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Lactational performance, enteric gas emissions, and plasma amino acid profile of dairy cows fed diets with soybean or canola meals included on an equal protein basis

Open ArchivePublished:January 14, 2021DOI:https://doi.org/10.3168/jds.2020-18851

      ABSTRACT

      This study investigated the effects of feeding solvent-extracted canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM) on an equivalent crude protein basis on performance, plasma AA profiles, enteric gas emissions, milk fatty acids, and nutrient digestibility in lactating dairy cows. Fifteen Holstein cows (95 ± 20 d in milk) were used in a replicated 3 × 3 Latin square design experiment with 3 periods of 28 d each. Treatments were 3 diets containing 17.1% CM, 14.2% ESBM, or 13.6% SSBM (dry matter basis). Vegetable oil was added (canola oil for CM or soybean oil for SSBM) to equalize the ether extract concentration of the diets. Rumen-protected Met was supplemented targeting digestible Met supply of 2.2% of metabolizable protein in all diets. Canola meal increased dry matter intake (DMI) by 5.9 and 8.9% in comparison with ESBM and SSBM, respectively. Milk urea nitrogen was lowest in CM, followed by SSBM, and was highest for ESBM. No differences were observed in feed efficiency, energy-corrected milk yield, and milk composition or component yields among treatments. Cows fed CM emitted less enteric CH4 per kg of DMI compared with both ESBM and SSBM, but CH4 emission intensity (CH4 per kg of energy-corrected milk) was similar among treatments. In summary, replacement of ESBM or SSBM with CM, on an equal crude protein basis, in the diet of lactating dairy cows enhanced DMI, but yields of energy-corrected milk and milk components and feed efficiency were similar among treatments.

      Key words

      INTRODUCTION

      Solvent-extracted soybean meal (SSBM) is a byproduct from the oil industry widely used as a protein supplement in farm animal diets. Over the past 40 yr, increased production of canola oil in North America led to an increased use of its byproduct, canola meal (CM), as a protein source in dairy cow rations. Comparative performance of dairy cows fed diets with SSBM or CM have been studied and 2 meta-analyses concluded that CM generally gives similar or greater DMI, milk yield (MY), and milk protein yield (
      • Huhtanen P.
      • Hetta M.
      • Swensson C.
      Evaluation of canola meal as a protein supplement for dairy cows: A review and a meta-analysis.
      ;
      • Martineau R.
      • Ouellet D.R.
      • Lapierre H.
      Feeding canola meal to dairy cows: A meta-analysis on lactational responses.
      ).
      Due to different environmental conditions during growth and harvest, as well as variations in cultivars and meal processing, Canadian solvent-extracted CM can vary substantially in its nutritional composition. A survey that analyzed CM samples from 12 Canadian processing plants over a 4-yr period observed that CM RUP content ranged from 43 to 51% (
      • Broderick G.A.
      • Colombini S.
      • Costa S.
      • Karsli M.A.
      • Faciola A.P.
      Chemical and ruminal in vitro evaluation of Canadian canola meals produced over 4 years.
      ), which is greater than the average RUP value for CM reported in the current
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      of 35.7% and is comparable to the RUP content of heat-treated or extruded soybean meal (ESBM; 49.5%;
      • Harper M.T.
      • Oh J.
      • Melgar A.
      • Nedelkov K.
      • Räisänen S.
      • Chen X.
      • Martins C.M.M.R.
      • Young M.
      • Ott T.L.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Production effects of feeding extruded soybean meal to early-lactation dairy cows.
      ).
      Extruded soybean meal, which is a different product from expeller soybean meal or other commercially available heat-treated SBM products, is produced by a process that includes initial grinding, preheating, and pressing of the beans through a die (
      • Björck I.
      • Asp N.G.
      The effects of extrusion cooking on nutritional value—A literature review.
      ). Previous work by
      • Giallongo F.
      • Oh J.
      • Frederick T.
      • Isenberg B.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Extruded soybean meal increased feed intake and milk production in dairy cows.
      demonstrated increased DMI and consequently MY in dairy cows fed diets in which SSBM was substituted by ESBM. However, we are not aware of any research comparing ESBM to CM. Comparing CM to ESBM, rather than SSBM, is appropriate because canola seeds, due to their high oil content, undergo an extrusion process before solvent extraction of the oil (
      • Unger E.H.
      Commercial processing of canola and rapeseed: Crushing and oil extraction.
      ). This extrusion, similar to the ESBM process, creates heat due to friction that increases RUP content of the resulting CM.
      Therefore, we hypothesized that an ESBM-based diet would be equivalent to a CM-based diet in terms of lactational performance of dairy cows, but the CM diet may outperform a SSBM-based diet. The specific objectives of the study were to investigate the effects of these 3 feed protein sources, fed on an equal CP basis (with added rumen-protected Met and vegetable oil), on lactational performance, plasma AA profiles, enteric gas emissions, milk fatty acids (FA), digestibility, and N excretions in lactating dairy cows.

      MATERIALS AND METHODS

      All procedures involving animals carried out in the experiment were approved by The Pennsylvania State University's Animal Care and Use Committee.

      Animals and Experimental Design

      The experiment was conducted in the tiestall barn of The Pennsylvania State University's Dairy Teaching and Research Center. Fifteen lactating Holstein cows (3 primiparous and 12 second-lactation cows), averaging (±SD) 95 (±20.0) DIM, 46.5 (±7.80) kg/d MY, and 585 (±37.8) kg of BW at the beginning of the study were used in a replicated 3 × 3 Latin square design balanced for carryover effects. Cows were grouped into 5 squares based on parity, DIM, and MY. Each experimental period lasted 28 d, with the first 18 d for adaptation to the diets, followed by 10 d for data and sample collection. Cows within square were randomly assigned to 1 of 3 treatment diets fed as TMR containing CM, ESBM, or SSBM as the main source of feed protein, included at 17.1%, 14.2%, and 13.6% of DM, respectively (Table 1). Our goal was to feed the same amount of CP from each protein source, rather than have the same physical inclusion rate. Vegetable oil was added to the SSBM (soybean oil; Sam's Club, Bentonville, AR) and CM (canola oil; Sam's Club, Bentonville, AR) diets to match the ether extract concentration of the ESBM diet. Rumen-protected Met (Mepron, Evonik Nutrition and Care GmbH, Hanau-Wolfgang, Germany) was used to achieve a target digestible Met supply of 2.2% of MP in all diets. Rumen escape and intestinal digestibility of Met in Mepron were assumed to be 80 and 90%, respectively, according to the manufacturer's specification. The Met concentration of diets was calculated based on AA analysis of CM, ESBM, and SSBM (analytical procedures specified below) and AA values based on
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      library for all other feed ingredients. Rumen-degraded and RUP values for the protein meals were derived from the in situ experiment (see below) and
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      feed library data were used for all other feed ingredients.
      Table 1Ingredients and chemical composition of diets containing canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM) fed in the experiment
      ItemDiet
      CMESBMSSBM
      Ingredient, % of DM
      Or as indicated.
       Corn silage
      Corn silage was 44.4% DM and contained (DM basis) 7.3% CP and 39.0% NDF.
      45.145.145.2
       Alfalfa haylage
      Alfalfa haylage was 31.9% DM and contained (DM basis) 21.7% CP and 41.3% NDF.
      11.011.011.0
       Hay-straw mixture
      Chopped (Standard Roto Grind Model 760, Roto Grind Tub Grinders, Greeley, CO) hay-straw mixture contained (DM basis) 11.5% CP.
      1.995.495.21
       Whole cottonseed5.985.995.98
       Corn grain, ground9.909.909.89
       SSBM13.6
       CM17.1
       ESBM14.2
       SoyPLUS
      SoyPLUS (West Central Cooperative, Ralston, IA) contained (DM basis) 46.6% CP.
      1.991.991.99
       Molasses
      Liquid molasses was from Westway Feed Products (Tomball, TX).
      4.914.914.91
       Vegetable oil
      Vegetable oil: canola oil in CM diet and soybean oil in SSBM diet.
      0.660.89
       Mepron
      Mepron is a rumen-protected Met source (Mepron, Evonik Nutrition and Care GmbH, Hanau-Wolfgang, Germany): 80% rumen by-pass fraction and 90% intestinal digestibility, based on manufacturer's specifications.
      0.050.080.08
       Mineral and vitamin premix
      The premix (Cargill Animal Nutrition, Cargill Inc., Roaring Spring, PA) contained (%, as-is basis) trace mineral mix, 0.86; MgO (56% Mg), 8.0; NaCl, 6.4; vitamin ADE premix (Cargill Animal Nutrition, Cargill Inc.), 0.48; limestone, 37.2; selenium premix (Cargill Animal Nutrition, Cargill Inc.), 0.07; and dry corn distillers grains with solubles, 46.7. Ca, 14.1%; P, 0.39%; Mg, 4.59%; K, 0.44%; S, 0.39%; Se, 6.91 mg/kg; Cu, 362 mg/kg; Zn, 1,085 mg/kg; Fe, 186 mg/kg, vitamin A, 276,717 IU/kg; vitamin D, 75,000 IU/kg; and vitamin E, 1,983 IU/kg.
      1.291.291.29
      CP supply from protein meals,
      Crude protein supply from CM, ESBM, and SSBM, respectively.
      g/kg of DMI
      70.070.069.0
      Composition, % of DM
       CP
      Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      16.316.716.6
       RDP
      Estimated based on NRC (2001) and in situ data from the current experiment for the protein meals using actual DMI, milk yield, milk composition, and BW of the cows throughout the experiment.
      8.208.709.50
       RUP
      Estimated based on NRC (2001) and in situ data from the current experiment for the protein meals using actual DMI, milk yield, milk composition, and BW of the cows throughout the experiment.
      8.108.007.10
       NDF
      Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      32.931.430.9
       ADF
      Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      22.220.720.6
       Ether extract
      Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      5.005.105.00
       NEL,
      Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      Mcal/kg of DM
      1.541.581.58
       NEL balance,
      Estimated based on NRC (2001) and in situ data from the current experiment for the protein meals using actual DMI, milk yield, milk composition, and BW of the cows throughout the experiment.
      Mcal/d
      0.60−0.10−0.20
       MP balance,
      Estimated based on NRC (2001) and in situ data from the current experiment for the protein meals using actual DMI, milk yield, milk composition, and BW of the cows throughout the experiment.
      Metabolizable protein balance estimated based on NRC (2001) using CM, ESBM, and SSBM protein degradability values estimated in the current in situ experiment.
      g/d
      93.028881.0
       Digestible Met,
      Estimated based on NRC (2001) and in situ data from the current experiment for the protein meals using actual DMI, milk yield, milk composition, and BW of the cows throughout the experiment.
      Metabolizable protein balance estimated based on NRC (2001) using CM, ESBM, and SSBM protein degradability values estimated in the current in situ experiment.
      g/d
      60.061.059.0
       NFC
      Estimated based on NRC (2001) and in situ data from the current experiment for the protein meals using actual DMI, milk yield, milk composition, and BW of the cows throughout the experiment.
      42.943.343.8
       Ca
      Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      0.720.640.69
       P
      Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      0.440.360.35
      1 Or as indicated.
      2 Corn silage was 44.4% DM and contained (DM basis) 7.3% CP and 39.0% NDF.
      3 Alfalfa haylage was 31.9% DM and contained (DM basis) 21.7% CP and 41.3% NDF.
      4 Chopped (Standard Roto Grind Model 760, Roto Grind Tub Grinders, Greeley, CO) hay-straw mixture contained (DM basis) 11.5% CP.
      5 SoyPLUS (West Central Cooperative, Ralston, IA) contained (DM basis) 46.6% CP.
      6 Liquid molasses was from Westway Feed Products (Tomball, TX).
      7 Vegetable oil: canola oil in CM diet and soybean oil in SSBM diet.
      8 Mepron is a rumen-protected Met source (Mepron, Evonik Nutrition and Care GmbH, Hanau-Wolfgang, Germany): 80% rumen by-pass fraction and 90% intestinal digestibility, based on manufacturer's specifications.
      9 The premix (Cargill Animal Nutrition, Cargill Inc., Roaring Spring, PA) contained (%, as-is basis) trace mineral mix, 0.86; MgO (56% Mg), 8.0; NaCl, 6.4; vitamin ADE premix (Cargill Animal Nutrition, Cargill Inc.), 0.48; limestone, 37.2; selenium premix (Cargill Animal Nutrition, Cargill Inc.), 0.07; and dry corn distillers grains with solubles, 46.7. Ca, 14.1%; P, 0.39%; Mg, 4.59%; K, 0.44%; S, 0.39%; Se, 6.91 mg/kg; Cu, 362 mg/kg; Zn, 1,085 mg/kg; Fe, 186 mg/kg, vitamin A, 276,717 IU/kg; vitamin D, 75,000 IU/kg; and vitamin E, 1,983 IU/kg.
      10 Crude protein supply from CM, ESBM, and SSBM, respectively.
      11 Values calculated using the chemical analysis (Cumberland Valley Analytical Services Inc., Waynesboro, PA) of the feed ingredients and their inclusion in the diets.
      12 Estimated based on
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      and in situ data from the current experiment for the protein meals using actual DMI, milk yield, milk composition, and BW of the cows throughout the experiment.
      13 Metabolizable protein balance estimated based on
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      using CM, ESBM, and SSBM protein degradability values estimated in the current in situ experiment.
      All 3 diets had similar ingredient composition and were formulated to meet or exceed NEL and MP requirements (
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      ) of a Holstein cow producing 46 kg of milk/d with 3.30% milk fat and 2.85% true protein at 27 kg/d DMI and BW of 611 kg. The SSBM was locally sourced (Cargill Inc., Roaring Spring, PA) and the ESBM was produced by Fabin Bros. (Indiana, PA) at 171°C extrusion temperature. The CM was purchased through Gavilon Group LLC (Omaha, NE) and was sourced from processing plants in Canada (Bunge in Harrowby, MB, and ADM in Windsor, ON, Canada). The 3 diets were mixed using a mobile mixer (Rissler Mobile TMR Mixer Model 1050, I. H. Rissler, Mohnton, PA) and were fed once daily (0700 h) as TMR to achieve 10% refusals. All cows had free access to drinking water and were milked twice daily (at approximately 0600 and 1800 h).

      Sampling and Measurements

      Individual feed intake (on as-fed basis) and MY of the cows were recorded daily throughout the experiment. Cow BW was also recorded twice daily for the entire experiment using an AfiFarm 3.04E scale system (S.A.E. Afikim, Rehovot, Israel) while cows exited the milk parlor. Total mixed ration and refusals from each diet were sampled twice weekly, and samples were composited (on an equal weight basis) by week and diet. Samples of individual forages (i.e., corn silage, alfalfa haylage, and the straw-hay mix) and concentrate feeds were collected weekly. Forages were composited by experimental period, whereas one composite sample for the entire experiment was prepared for each concentrate feed ingredient. All feed samples were stored at −20°C until analysis. Samples were dried for DM determination at 55°C for 72 h in a forced-air oven, and ground in a Wiley Mill (1-mm screen; Thomas Scientific, Swedesboro, NJ) for further analyses. Feed DMI was calculated from the as-fed TMR intake using the DM content of the weekly composited TMR and refusals samples. Composite samples of individual feed ingredients were analyzed by wet chemistry methods for CP (method 990.03;
      • AOAC International
      Official Methods of Analysis.
      ), RDP and RUP (CM, ESBM, and SSBM only; using an in situ procedure described below), amylase-treated NDF (
      • Van Soest P.J.
      • Robertson J.B.
      • Lewis B.A.
      Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition.
      ), ADF (method 973.18;
      • AOAC International
      Official Methods of Analysis.
      ), ether extract (method 2003.05;
      • AOAC International
      Official Methods of Analysis.
      ), ash (method 942.05;
      • AOAC International
      Official Methods of Analysis.
      ), Ca and P (method 985.01;
      • AOAC International
      Official Methods of Analysis.
      ), and estimated NFC and NEL by Cumberland Valley Analytical Services Inc. (Waynesboro, PA). The analyzed composition of the feed ingredients and their inclusion rate in the TMR were used to compute CP, NDF, ADF, ether extract, Ca, and P concentration of the diets (Table 1). Dietary supplies of NEL, MP, and digestible Met were estimated using
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      based on actual DMI, MY, milk composition, and BW of the cows during the experiment. Concentrations of MP, RDP, and RUP were estimated based on in situ data derived in the current study for CM, ESBM, and SSBM and
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      values for the other feed ingredients. Composite TMR samples were analyzed for starch according to
      • Hall M.B.
      Determination of starch, including maltooligosaccharides, in animal feeds: Comparison of methods and a method recommended for AOAC collaborative study.
      and indigestible NDF (iNDF) as described by
      • Huhtanen P.
      • Kaustell K.
      • Jaakkola S.
      The use of internal markers to predict total digestibility and duodenal flow of nutrients in cattle given six different diets.
      and modified by
      • Lee C.
      • Hristov A.N.
      • Cassidy T.W.
      • Heyler K.S.
      • Lapierre H.
      • Varga G.A.
      • De Veth M.J.
      • Patton R.A.
      • Parys C.
      Rumen-protected lysine, methionine, and histidine increase milk protein yield in dairy cows fed a metabolizable protein-deficient diet.
      . Samples of SSBM, CM, and ESBM were also analyzed for AA composition at the University of Missouri–Columbia's Agricultural Experiment Station Chemical Laboratory (Columbia, MO) following the procedures of
      • Deyl Z.
      • Hyanek J.
      • Horakova M.
      Profiling of amino acids in body fluids and tissues by means of liquid chromatography.
      and
      • Fekkes D.
      State-of-the-art of high-performance liquid chromatographic analysis of amino acids in physiological samples.
      . Amino acid composition of the other feed ingredients was analyzed with ion-exchange chromatography by Evonik Nutrition & Care GmbH (Hanau-Wolfgang, Germany;
      • AOAC International
      Official Method of Analysis.
      ;
      • European Commission
      2009/150/EC Commission regulation laying down the methods of sampling and analysis for the official control of feed.
      ). Intestinal digestibility of CM, ESBM, and SSBM protein was analyzed at Rock River Laboratories Inc. (Watertown, WI) using the 3-step procedure of
      • Calsamiglia S.
      • Stern M.D.
      A three-step in vitro procedure for estimating intestinal digestion of protein in ruminants.
      .
      During the last week of each experimental period, 8 spot fecal and urine samples were collected in 3 consecutive days at intervals staggered in time to cover a 24-h period starting at 0500, 1100, 1700, and 2300 h (d 1), 0800, 1400, and 2000 h (d 2), and 0200 h (d 3). Fecal samples were oven-dried at 55°C for 72 h, ground through a 1-mm sieve in a Wiley Mill (Thomas Scientific), composited per cow and experimental period, and then analyzed DM, OM, CP, NDF, ADF, iNDF, and starch as described above. Total-tract apparent digestibility of DM, OM, NDF, ADF, CP, and starch was estimated using iNDF as an internal digestibility marker (
      • Schneider B.H.
      • Flatt W.P.
      The Evaluation of Feeds through Digestibility Experiments.
      ). Urine samples were processed and analyzed for allantoin, uric acid, creatinine, urinary urea N (UUN), and total N. Total N was analyzed in freeze-dried urine samples of approximately 60 µL of 1:10 diluted and acidified urine using a Costech ECS 4010 C/N/S elemental analyzer (Costech Analytical Technologies Inc., Valencia, CA). Stanbio Laboratory (Boerne, TX) kits were used to analyze UUN (Urea Nitrogen Kit 580), creatinine (Creatinine Kit 420), and uric acid (Uric Acid Kit 1045). Allantoin was analyzed following the procedure by
      • Chen X.B.
      • Chen Y.K.
      • Franklin M.F.
      • Ørskov E.R.
      • Shand W.J.
      The effect of feed intake and body weight on purine derivative excretion and microbial protein supply in sheep.
      . Daily volume of excreted urine was estimated based on urinary creatinine concentration, assuming a creatinine excretion rate of 29 mg/kg of BW based on total urine collection data from
      • Hristov A.N.
      • Lee C.
      • Cassidy T.
      • Long M.
      • Heyler K.
      • Corl B.
      • Forster R.
      Effects of lauric and myristic acids on ruminal fermentation, production, and milk fatty acid composition in lactating dairy cows.
      . Daily total N, urinary urea, and purine derivative excretions were calculated based on the estimated urine output.
      Blood samples were collected from the tail vein or artery into EDTA vacutainers (Becton, Dickinson and Company, Franklin Lakes, NJ) 4 times in 2 consecutive days at 0900 and 1700 h (d 1) and 1400 and 2000 h (d 2). Blood plasma was separated, processed (
      • Lee C.
      • Hristov A.N.
      • Cassidy T.W.
      • Heyler K.S.
      • Lapierre H.
      • Varga G.A.
      • De Veth M.J.
      • Patton R.A.
      • Parys C.
      Rumen-protected lysine, methionine, and histidine increase milk protein yield in dairy cows fed a metabolizable protein-deficient diet.
      ), and composited on an equal volume basis per cow and period for analysis of AA at the University of Missouri–Columbia's Agricultural Experiment Station Chemical Laboratory as described above.
      Milk samples were collected from 2 consecutive milkings (evening and morning) on 2 separate days (i.e., a total of 4 milkings) during wk 4 of each experimental period. Milk samples were preserved with 2-bromo-2-nitropropane-1,3 diol and submitted to Dairy One Laboratory (Ithaca, NY) for analysis of fat, true protein, lactose, and MUN using infrared spectroscopy and Milkoscan models 6000, FT+, or 7 and Fossomatic models 5000 of FC (Foss Electric A/S, Hillerød, Denmark). Energy-corrected milk was calculated according to
      • Sjaunja L.O.
      • Baevre L.
      • Junkkarinen L.
      • Pedersen J.
      • Setälä J.
      A Nordic proposal for an energy corrected milk (ECM) formula.
      : ECM (kg/d) = kg of milk × [(38.3 × % fat × 10 + 24.2 × % true protein × 10 + 16.54 × % lactose × 10 + 20.7) ÷ 3,140]. Evening and morning milk samples were analyzed separately to weigh the milk component concentrations for evening and morning MY. A separate unpreserved milk sample (from all 4 milkings) was stored at −20°C, composited on an equal volume basis per cow and period, and analyzed for FA as described by
      • Rico D.E.
      • Harvatine K.J.
      Induction of and recovery from milk fat depression occurs progressively in dairy cows switched between diets that differ in fiber and oil concentration.
      .
      Enteric CH4, CO2, and H2 emissions were measured using the GreenFeed system (C-Lock Inc., Rapid City, SD) as described by
      • Hristov A.N.
      • Oh J.
      • Giallongo F.
      • Frederick T.
      • Weeks H.
      • Zimmerman P.R.
      • Harper M.T.
      • Hristova R.A.
      • Zimmerman R.S.
      • Branco A.F.
      The use of an automated system (GreenFeed) to monitor enteric methane and carbon dioxide emissions from ruminant animals.
      . Briefly, measurements occurred 8 times in 3 d, covering a 24-h period as follows: 0900, 1500, and 2100 h (d 1), 0300, 1200, and 1700 h (d 2), and 0000 and 0500 h (d 3). Individual breath gas samples were collected for 5 min, followed by 2-min background air sample collection.
      A subexperiment was conducted to determine in situ ruminal degradability of CP of CM, ESBM, and SSBM. Three cows were used in the in situ experiment and were fed (% of DM) the following: corn silage, 43.4; alfalfa haylage, 12.0; grass-hay mix, 3.40; ground corn grain, 8.70; whole roasted soybeans, 8.00; SoyPLUS (Landus Cooperative, Ames, IA), 5.01; canola meal, 8.49; cottonseed hulls, 5.01; molasses, 4.49; and a mineral and vitamin premix, 1.50 (Cargill Animal Nutrition, Cargill Inc., Roaring Spring, PA). The experimental procedures were as described by
      • Lee C.
      • Hristov A.N.
      • Cassidy T.W.
      • Heyler K.S.
      • Lapierre H.
      • Varga G.A.
      • De Veth M.J.
      • Patton R.A.
      • Parys C.
      Rumen-protected lysine, methionine, and histidine increase milk protein yield in dairy cows fed a metabolizable protein-deficient diet.
      . Samples of all 3 meals were collected throughout the experiment and composited at the end of the experiment. The composite samples were used for the in situ experiment. Triplicate samples of 7 g each (as-fed basis and without further processing) were weighed into Ankom nylon bags (10 cm × 20 cm forage bag; Ankom Technology Corp., Macedon, NY), which were sequentially incubated in the ventral rumen for 2, 4, 8, 24, and 48 h and simultaneously removed. It is noted that a 16-h time point (recommended by
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      ) was not used in the in situ experiment. Samples were not pre-soaked before placed into the rumen. Following incubation, all bags were manually washed, including the 0 h samples, which were not incubated in the rumen, with cold tap water until the water ran clean. All samples were oven-dried for 72 h at 55°C and aliquots of each bag residue were pulverized using a Mixer Mill MM 200 (Retsch GmbH, Haan, Germany) and analyzed for N using an elemental analyzer (Costech ECS 4010 C/N/S, Costech Analytical Technologies Inc., Valencia, CA) to calculate CP (N × 6.25). Ruminal disappearance was calculated based on average per cow and incubation time point, of initial dry weight of the incubated sample, dry weight of the residues, and N content of the incubated samples and bag residues. Degradation data were fitted to a 3-parameter, exponential rise to a maximum model: p = a + b × (1 – ect), with the constraint that a + b ≤ 100%, using SigmaPlot v. 10.0 (Systat Software Inc., San Jose, CA), where p is the degraded fraction of CP at time t, a is the soluble fraction (or intercept), b is the potentially degradable fraction of CP, and c is the rate of degradation of fraction b (
      • Ørskov E.R.
      • McDonald I.
      The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage.
      ). Effective degradability (ED; percentage of CP that would be potentially degraded in the rumen at specified passage rate) was estimated using the equation of
      • Ørskov E.R.
      • McDonald I.
      The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage.
      : ED = a + b × [c ÷ (c + k)], where a, b, and c are as specified above and k is the rate of passage assumed to be 6%/h.

      Statistical Analysis

      All data were analyzed using the MIXED procedure of SAS, version 9.4 (SAS Institute Inc., Cary, NC). Milk yield and DMI data for the last 10 d of each experimental period were used in the statistical analysis. Feed efficiency (MY ÷ DMI) was estimated based on MY and DMI data over the last 10 d of each experimental period. These data were analyzed as repeated measures. The statistical model included treatment, experimental period, the repeated term (day), and treatment × day interaction. Square and cow within square were random effects and all others were fixed. The best covariance structure for repeated measures was chosen by the lowest corrected Akaike information criterion, which was AR(1) for DMI and MY, VC for BW, and CS for feed efficiency. Milk composition and component yield data were averaged per cow and per period, and the average values were used in the statistical analysis and to calculate ECM. For ECM feed efficiency (ECM ÷ DMI), the 10-d average DMI was used. Enteric gas emission data were averaged across all sampling points and the average values per cow and per period were used in the statistical analysis. Milk composition, plasma AA, milk FA, enteric gas emissions, digestibility, and N and purine derivative excretion data were analyzed with the model described above, excluding the repeated term and its interaction with treatment. The in situ degradability data were analyzed with protein source in the model. When the main effect of treatment or protein source were significant, means were separated by pairwise t-test (pdiff option of PROC MIXED) with Tukey's adjustment. Mean differences were considered significant at P ≤ 0.05, trends were declared at 0.05 < P ≤ 0.10, and numerical differences were declared at 0.10 < P ≤ 0.15. Data are presented as least squares means.

      RESULTS

      Diet and Feed Composition

      Dietary ingredients and chemical composition of the diets fed are shown in Table 1. All 3 diets had similar ingredient composition, except that the SBM diets had a greater hay-straw mixture inclusion to achieve similar NDF values as for the CM diet. Differences in the CP content of the hay-straw mixture throughout the experiment resulted in slight differences in CP concentration of the CM and SBM diets.
      The CM diet provided NEL in excess of the cow's requirements (
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      ) and the ESBM and SSBM diets were slightly below NEL requirements. All 3 diets provided MP and RUP in excess of the
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      recommendations, but were 15.7, 11.6, and 3.8% deficient in estimated RDP supply (CM, ESBM, and SSBM diets, respectively; RDP and RUP balance not shown in Table 1). In addition, diets provided an estimated (
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      ) digestible Met supply of 1.96, 1.93, and 2.05% of MP (respectively), which was below the 2.2% recommended by
      • Schwab C.G.
      • Huhtanen P.
      • Hunt C.W.
      • Hvelplund T.
      Nitrogen requirements in cattle.
      .
      Chemical and AA composition of the meals is presented in Table 2. The ESBM and SSBM had 20 and 25% (respectively) greater CP concentration than CM. The RUP content of CM was greater than expected based on average
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      values (36% of CP). Likewise, analyzed RUP content of SSBM was 14.4% greater than the average
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      value (43%). Intestinal digestibility of RUP was greater for ESBM, in comparison with CM and SSBM (by 21.6% and 7.8%, respectively). As expected, CM had on average 3.8 times greater NDF content than the SBM meals.
      Table 2Chemical composition and AA concentration of canola meal (CM), extruded soybean meal (ESBM), and solvent-extracted soybean meal (SSBM) fed to lactating dairy cows in the experiment
      ItemProtein meal
      CMESBMSSBM
      CP,
      Analyzed by Cumberland Valley Analytical Services Inc. (Waynesboro, PA) using wet chemistry methods.
      % DM
      40.749.051.0
       RDP,
      Estimated using in situ values and NRC (2001) equations to calculate RDP and RUP.
      % of CP
      36.838.950.8
       RUP,
      Estimated using in situ values and NRC (2001) equations to calculate RDP and RUP.
      % of CP
      63.261.149.2
      RUP intestinal digestibility,
      Analyzed by Rock River Laboratories Inc. (Watertown, WI) using the Calsamiglia and Stern (1995) method.
      % of RUP
      81.899.592.3
      NDF
      Analyzed by Cumberland Valley Analytical Services Inc. (Waynesboro, PA) using wet chemistry methods.
      30.39.006.90
      ADF
      Analyzed by Cumberland Valley Analytical Services Inc. (Waynesboro, PA) using wet chemistry methods.
      20.73.904.30
      Ash
      Analyzed by Cumberland Valley Analytical Services Inc. (Waynesboro, PA) using wet chemistry methods.
      7.735.997.74
      Ca
      Analyzed by Cumberland Valley Analytical Services Inc. (Waynesboro, PA) using wet chemistry methods.
      0.860.290.75
      P
      Analyzed by Cumberland Valley Analytical Services Inc. (Waynesboro, PA) using wet chemistry methods.
      1.160.720.70
      EAA,
      Analyzed by University of Missouri–Columbia's Agricultural Experiment Station Chemical Laboratories (Columbia, MO) following the procedures of Deyl et al. (1986) and Fekkes (1996).
      % of CP
       Arg5.587.357.27
       His2.682.652.58
       Ile4.285.054.92
       Leu6.937.797.61
       Lys5.856.686.41
       Met1.991.391.37
       Phe3.925.165.02
       Thr4.143.853.72
       Trp1.161.501.34
       Val5.054.924.77
       Total EAA41.646.345.0
      NEAA,
      Analyzed by University of Missouri–Columbia's Agricultural Experiment Station Chemical Laboratories (Columbia, MO) following the procedures of Deyl et al. (1986) and Fekkes (1996).
      % of CP
       Ala4.364.424.29
       Asp5.587.357.27
       Cys2.571.501.47
       Glu16.518.317.8
       Gly5.134.444.37
       Pro6.405.505.40
       Ser3.424.314.16
       Tyr2.543.633.61
       Total NEAA46.549.448.3
       Total EAA and NEAA88.195.793.3
      1 Analyzed by Cumberland Valley Analytical Services Inc. (Waynesboro, PA) using wet chemistry methods.
      2 Estimated using in situ values and
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      equations to calculate RDP and RUP.
      3 Analyzed by Rock River Laboratories Inc. (Watertown, WI) using the
      • Calsamiglia S.
      • Stern M.D.
      A three-step in vitro procedure for estimating intestinal digestion of protein in ruminants.
      method.
      4 Analyzed by University of Missouri–Columbia's Agricultural Experiment Station Chemical Laboratories (Columbia, MO) following the procedures of
      • Deyl Z.
      • Hyanek J.
      • Horakova M.
      Profiling of amino acids in body fluids and tissues by means of liquid chromatography.
      and
      • Fekkes D.
      State-of-the-art of high-performance liquid chromatographic analysis of amino acids in physiological samples.
      .
      Concentrations of Arg, Ile, Leu, Lys, Phe, and Trp in the meal CP were greater in SBM than CM. Concentrations of Thr, Val, and Met were greater in CM than SBM. Overall, concentration of total EAA was greater for the SBM products than CM. Concentrations of most individual and total NEAA were greater in SBM than CM, except for Cys, Gly, and Pro, which were greater in CM than in SBM. The sum of EAA + NEAA was on average 7% lower for CM in comparison with ESBM and SSBM.
      The in situ CP degradability data for the 3 meals are shown in Table 3. The soluble fraction (a) tended to be greater (P = 0.10) and the potentially degradable fraction (b) of CP tended to be lower (P = 0.10) for SBM than CM. The rate of degradation of fraction b CP was 67% greater (P = 0.01) for SSBM than CM or ESBM. Effective degradability of CP, estimated at an assumed 6%/h rate of passage, was also 38 and 30% greater (P = 0.01) for SSBM than CM and ESBM, respectively.
      Table 3Ruminal in situ degradability of canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM) CP
      Values are model estimates of in situ CP disappearance curves. Data were fitted to the equation a + b × (1 – e−ct), with the constraint that a + b ≤100%, using SigmaPlot v. 10.0 (Systat Software Inc., San Jose, CA), where p is the degraded fraction of CP at time t, a is the soluble fraction of CP (or intercept), b is the potentially degradable fraction of CP, and c is the rate of degradation of fraction b (Ørskov and McDonald, 1979).
      ItemMealSEMP-value
      CMESBMSSBM
      Soluble fraction (a), %5.8010.813.11.520.10
      Potentially degradable fraction (b), %94.289.286.91.510.10
      Rate of degradation of b, %/h0.03
      Means within a row with different superscripts differ (P < 0.05).
      0.03
      Means within a row with different superscripts differ (P < 0.05).
      0.05
      Means within a row with different superscripts differ (P < 0.05).
      0.0040.01
      Effective degradability,
      Effective degradability (ED) was estimated using the equation of Ørskov and McDonald (1979): ED = a + b × [c ÷ (c + k)], where a,b, and c are as specified above and k is the rate of passage assumed to be 6%/h.
      %
      36.7
      Means within a row with different superscripts differ (P < 0.05).
      38.8
      Means within a row with different superscripts differ (P < 0.05).
      50.6
      Means within a row with different superscripts differ (P < 0.05).
      2.060.01
      a,b Means within a row with different superscripts differ (P < 0.05).
      1 Values are model estimates of in situ CP disappearance curves. Data were fitted to the equation a + b × (1 – ect), with the constraint that a + b ≤100%, using SigmaPlot v. 10.0 (Systat Software Inc., San Jose, CA), where p is the degraded fraction of CP at time t, a is the soluble fraction of CP (or intercept), b is the potentially degradable fraction of CP, and c is the rate of degradation of fraction b (
      • Ørskov E.R.
      • McDonald I.
      The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage.
      ).
      2 Effective degradability (ED) was estimated using the equation of
      • Ørskov E.R.
      • McDonald I.
      The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage.
      : ED = a + b × [c ÷ (c + k)], where a,b, and c are as specified above and k is the rate of passage assumed to be 6%/h.

      Feed Intake and Milk Production and Composition

      The CM diet increased (P < 0.001) DMI by 2.4 and 1.6 kg/d compared with ESBM and SSBM diets, respectively (Table 4). Compared with SSBM, the CM and ESBM diets increased (P = 0.002) MY by 2.7 and 1.5 kg/d, respectively. No differences in MY between CM and ESBM diets were observed and treatments did not affect feed efficiency. Milk urea nitrogen concentration was lowest (P < 0.001) in CM, followed by SSBM, and was highest for ESBM. Treatments did not affect milk composition and component yields, ECM yield, and ECM feed efficiency. There was a trend for lower (P = 0.11) BW of the cows when fed the CM versus both SBM diets, but this experiment was not designed to investigate effects on BW.
      Table 4Dry matter intake, BW, and milk production variables in dairy cows fed diets containing canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM)
      ItemDietSEM
      Largest SEM published in table; n = 438 for DMI; n = 421 for milk yield; n = 413 for milk yield ÷ DMI; n = 44 for milk composition variables; and n = 450 for BW (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      P-value
      Main effect of treatment.
      CMESBMSSBM
      DMI, kg/d26.9
      Means within a row with different superscripts differ (P < 0.05).
      25.3
      Means within a row with different superscripts differ (P < 0.05).
      24.5
      Means within a row with different superscripts differ (P < 0.05).
      0.82<0.001
      ESBM versus SSBM, P = 0.12.
      Milk yield, kg/d43.8
      Means within a row with different superscripts differ (P < 0.05).
      42.6
      Means within a row with different superscripts differ (P < 0.05).
      41.1
      Means within a row with different superscripts differ (P < 0.05).
      1.890.002
       Milk yield ÷ DMI, kg/kg1.641.701.700.0390.35
      Milk fat, %3.663.643.650.1250.99
       Milk fat, kg/d1.601.551.540.0920.67
      Milk true protein, %3.103.093.170.0410.17
       Milk true protein, kg/d1.361.321.340.0770.82
      Milk lactose, %4.784.854.810.0360.19
       Milk lactose, kg/d2.102.082.050.1050.86
      MUN, mg/dL9.23
      Means within a row with different superscripts differ (P < 0.05).
      12.0
      Means within a row with different superscripts differ (P < 0.05).
      10.4
      Means within a row with different superscripts differ (P < 0.05).
      0.40<0.001
      ECM,
      Sjaunja et al. (1990).
      kg/d
      41.440.340.32.200.74
       ECM ÷ DMI, kg/kg1.561.651.660.0630.32
      Milk NEL,
      According to NRC (2001).
      Mcal/d
      30.830.130.01.640.74
      BW, kg6025985945.790.11
      a–c Means within a row with different superscripts differ (P < 0.05).
      1 Largest SEM published in table; n = 438 for DMI; n = 421 for milk yield; n = 413 for milk yield ÷ DMI; n = 44 for milk composition variables; and n = 450 for BW (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      2 Main effect of treatment.
      3 ESBM versus SSBM, P = 0.12.
      4
      • Sjaunja L.O.
      • Baevre L.
      • Junkkarinen L.
      • Pedersen J.
      • Setälä J.
      A Nordic proposal for an energy corrected milk (ECM) formula.
      .
      5 According to
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      .

      Plasma Amino Acids

      Compared with CM and SSBM, the ESBM diet increased (P ≤ 0.05) plasma concentrations of Ile, Leu, Val, and the sum of EAA and had lower (P < 0.005) Met concentration (Table 5). In addition, the ESBM diet increased (P < 0.005) plasma concentrations of Cit and decreased that of Cys compared with the CM and SSBM diets. The SSBM diet had lower concentration of 1-methylhistidine than both ESBM and CM (P < 0.001). The CM diet had lower (P < 0.001) plasma urea concentration in comparison with the SBM diets.
      Table 5Blood plasma AA concentration (μM) in dairy cows fed diets containing canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM)
      ItemDietSEM
      Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis).
      P-value
      Main effect of treatment.
      CMESBMSSBM
      Arg78.984.079.14.560.29
      His48.051.446.32.450.29
      Ile129
      Means within a row with different superscripts differ (P < 0.05).
      153
      Means within a row with different superscripts differ (P < 0.05).
      128
      Means within a row with different superscripts differ (P < 0.05).
      5.52<0.001
      Leu142
      Means within a row with different superscripts differ (P < 0.05).
      171
      Means within a row with different superscripts differ (P < 0.05).
      132
      Means within a row with different superscripts differ (P < 0.05).
      5.75<0.001
      Lys80.683.280.13.330.69
      Met25.4
      Means within a row with different superscripts differ (P < 0.05).
      20.0
      Means within a row with different superscripts differ (P < 0.05).
      23.0
      Means within a row with different superscripts differ (P < 0.05).
      0.920.001
      Phe46.4
      Means within a row with different superscripts differ (P < 0.05).
      49.1
      Means within a row with different superscripts differ (P < 0.05).
      42.2
      Means within a row with different superscripts differ (P < 0.05).
      1.590.005
      Thr10293.495.65.270.36
      Trp30.0
      Means within a row with different superscripts differ (P < 0.05).
      29.4
      Means within a row with different superscripts differ (P < 0.05).
      27.3
      Means within a row with different superscripts differ (P < 0.05).
      0.930.04
      Val271
      Means within a row with different superscripts differ (P < 0.05).
      302
      Means within a row with different superscripts differ (P < 0.05).
      250
      Means within a row with different superscripts differ (P < 0.05).
      9.15<0.001
      ∑EAA
      Sum of EAA (Arg, His, Ile, Leu, Lys, Phe, Thr, Trp, and Val).
      953
      Means within a row with different superscripts differ (P < 0.05).
      1,036
      Means within a row with different superscripts differ (P < 0.05).
      904
      Means within a row with different superscripts differ (P < 0.05).
      30.00.002
      ∑EAA without Met927
      Means within a row with different superscripts differ (P < 0.05).
      1,016
      Means within a row with different superscripts differ (P < 0.05).
      881
      Means within a row with different superscripts differ (P < 0.05).
      29.50.001
      Ala26323624510.20.08
      Asn44.550.446.02.290.07
      Asp5.09
      Means within a row with different superscripts differ (P < 0.05).
      7.09
      Means within a row with different superscripts differ (P < 0.05).
      6.23
      Means within a row with different superscripts differ (P < 0.05).
      0.580.02
      Cit71.2
      Means within a row with different superscripts differ (P < 0.05).
      80.6
      Means within a row with different superscripts differ (P < 0.05).
      70.9
      Means within a row with different superscripts differ (P < 0.05).
      3.450.006
      Cys1.95
      Means within a row with different superscripts differ (P < 0.05).
      1.27
      Means within a row with different superscripts differ (P < 0.05).
      1.59
      Means within a row with different superscripts differ (P < 0.05).
      0.08<0.001
      Gln2432412499.540.66
      Glu54.653.851.92.160.50
      Gly28327928611.80.87
      Orn43.848.442.42.240.10
      Pro78.782.374.54.100.16
      Ser76.579.874.33.410.24
      Tau50.250.447.53.800.64
      Tyr48.148.644.41.930.10
      ∑NEAA
      Sum of NEAA (Ala, Asn, Asp, Cys, Cit, Gln, Glu, Gly, Orn, Pro, Ser, Tau, and Tyr were considered as NEAA).
      1,2731,2681,25135.00.85
      ∑TAA
      Sum of total AA.
      2,2262,3042,15460.00.11
      Carnosine14.214.313.50.550.39
      1-MH
      MH = methylhistidine.
      18.0
      Means within a row with different superscripts differ (P < 0.05).
      17.7
      Means within a row with different superscripts differ (P < 0.05).
      15.0
      Means within a row with different superscripts differ (P < 0.05).
      1.43<0.001
      3-MH
      MH = methylhistidine.
      3.773.573.470.170.22
      Urea3,433
      Means within a row with different superscripts differ (P < 0.05).
      4,695
      Means within a row with different superscripts differ (P < 0.05).
      4,397
      Means within a row with different superscripts differ (P < 0.05).
      114<0.001
      a–c Means within a row with different superscripts differ (P < 0.05).
      1 Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis).
      2 Main effect of treatment.
      3 Sum of EAA (Arg, His, Ile, Leu, Lys, Phe, Thr, Trp, and Val).
      4 Sum of NEAA (Ala, Asn, Asp, Cys, Cit, Gln, Glu, Gly, Orn, Pro, Ser, Tau, and Tyr were considered as NEAA).
      5 Sum of total AA.
      6 MH = methylhistidine.

      Milk Fatty Acids

      Compared with ESBM and SSBM, the CM diet increased (P ≤ 0.03) concentrations of 18:1, 20:0, and MUFA in milk fat (Table 6). On the other hand, ESBM increased (P ≤ 0.001) concentrations of 17:0. 18:2, 18:3, and PUFA in comparison with both CM and SSBM. The SSBM diet increased (P ≤ 0.002) concentrations of 16:0 and SFA and decreased (P < 0.001) preformed FA.
      Table 6Fatty acid (FA) composition of milk fat (g/100 g of total FA) in dairy cows fed diets containing canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM)
      ItemDietSEM
      Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      P-value
      Main effect of treatment.
      CMESBMSSBM
      4:04.524.654.410.110.07
      6:02.32
      Means within a row with different superscripts differ (P < 0.05).
      2.43
      Means within a row with different superscripts differ (P < 0.05).
      2.35
      Means within a row with different superscripts differ (P < 0.05).
      0.040.02
      8:01.27
      Means within a row with different superscripts differ (P < 0.05).
      1.34
      Means within a row with different superscripts differ (P < 0.05).
      1.30
      Means within a row with different superscripts differ (P < 0.05).
      0.030.02
      10:02.822.922.960.110.13
      12:03.153.233.370.130.11
      14:010.1
      Means within a row with different superscripts differ (P < 0.05).
      10.3
      Means within a row with different superscripts differ (P < 0.05).
      10.7
      Means within a row with different superscripts differ (P < 0.05).
      0.240.02
      cis-9 14:10.81
      Means within a row with different superscripts differ (P < 0.05).
      0.87
      Means within a row with different superscripts differ (P < 0.05).
      0.92
      Means within a row with different superscripts differ (P < 0.05).
      0.030.03
      15:01.02
      Means within a row with different superscripts differ (P < 0.05).
      0.94
      Means within a row with different superscripts differ (P < 0.05).
      1.10
      Means within a row with different superscripts differ (P < 0.05).
      0.0490.04
      16:026.1
      Means within a row with different superscripts differ (P < 0.05).
      27.0
      Means within a row with different superscripts differ (P < 0.05).
      28.6
      Means within a row with different superscripts differ (P < 0.05).
      0.872<0.001
      cis-9 16:11.25
      Means within a row with different superscripts differ (P < 0.05).
      1.26
      Means within a row with different superscripts differ (P < 0.05).
      1.37
      Means within a row with different superscripts differ (P < 0.05).
      0.0890.02
      17:00.51
      Means within a row with different superscripts differ (P < 0.05).
      0.48
      Means within a row with different superscripts differ (P < 0.05).
      0.51
      Means within a row with different superscripts differ (P < 0.05).
      0.0110.003
      18:012.1
      Means within a row with different superscripts differ (P < 0.05).
      11.1
      Means within a row with different superscripts differ (P < 0.05).
      10.5
      Means within a row with different superscripts differ (P < 0.05).
      0.4790.004
      trans-4 18:10.04
      Means within a row with different superscripts differ (P < 0.05).
      0.03
      Means within a row with different superscripts differ (P < 0.05).
      0.03
      Means within a row with different superscripts differ (P < 0.05).
      0.002<0.001
      trans-5 18:10.023
      Means within a row with different superscripts differ (P < 0.05).
      0.017
      Means within a row with different superscripts differ (P < 0.05).
      0.016
      Means within a row with different superscripts differ (P < 0.05).
      0.001<0.001
      trans-6,8 18:10.44
      Means within a row with different superscripts differ (P < 0.05).
      0.36
      Means within a row with different superscripts differ (P < 0.05).
      0.36
      Means within a row with different superscripts differ (P < 0.05).
      0.018<0.001
      trans-9 18:10.35
      Means within a row with different superscripts differ (P < 0.05).
      0.30
      Means within a row with different superscripts differ (P < 0.05).
      0.30
      Means within a row with different superscripts differ (P < 0.05).
      0.011<0.001
      trans-10 18:10.770.720.710.0600.62
      trans-11 18:11.391.331.310.0890.52
      trans-12 18:10.65
      Means within a row with different superscripts differ (P < 0.05).
      0.59
      Means within a row with different superscripts differ (P < 0.05).
      0.61
      Means within a row with different superscripts differ (P < 0.05).
      0.0310.05
      cis-9 18:119.8
      Means within a row with different superscripts differ (P < 0.05).
      18.8
      Means within a row with different superscripts differ (P < 0.05).
      18.1
      Means within a row with different superscripts differ (P < 0.05).
      0.4690.001
      cis-11 18:11.05ª0.78
      Means within a row with different superscripts differ (P < 0.05).
      0.78
      Means within a row with different superscripts differ (P < 0.05).
      0.029<0.001
      cis-9,cis-12 18:22.22
      Means within a row with different superscripts differ (P < 0.05).
      3.18
      Means within a row with different superscripts differ (P < 0.05).
      2.26
      Means within a row with different superscripts differ (P < 0.05).
      0.078<0.001
      cis-6,cis-9,cis-12 18:30.018
      Means within a row with different superscripts differ (P < 0.05).
      0.028
      Means within a row with different superscripts differ (P < 0.05).
      0.023
      Means within a row with different superscripts differ (P < 0.05).
      0.001<0.001
      cis-9,cis-12,cis-15 18:30.40
      Means within a row with different superscripts differ (P < 0.05).
      0.50
      Means within a row with different superscripts differ (P < 0.05).
      0.36
      Means within a row with different superscripts differ (P < 0.05).
      0.010<0.001
      20:00.14
      Means within a row with different superscripts differ (P < 0.05).
      0.12
      Means within a row with different superscripts differ (P < 0.05).
      0.11
      Means within a row with different superscripts differ (P < 0.05).
      0.004<0.001
      cis-9,trans-11 CLA0.590.610.620.0370.51
      Others2.342.242.370.0940.12
      Total trans FA4.173.853.830.1980.05
      ΣSFA66.0
      Means within a row with different superscripts differ (P < 0.05).
      66.5
      Means within a row with different superscripts differ (P < 0.05).
      68.0
      Means within a row with different superscripts differ (P < 0.05).
      0.6310.002
      ΣMUFA28.1
      Means within a row with different superscripts differ (P < 0.05).
      26.6
      Means within a row with different superscripts differ (P < 0.05).
      26.1
      Means within a row with different superscripts differ (P < 0.05).
      0.541<0.001
      ΣPUFA3.50
      Means within a row with different superscripts differ (P < 0.05).
      4.66
      Means within a row with different superscripts differ (P < 0.05).
      3.57
      Means within a row with different superscripts differ (P < 0.05).
      0.109<0.001
      ΣDe novo
      De novo FA (<C16) are synthesized by the mammary gland; preformed FA (>C16) originate primarily from extraction from plasma; and mixed FA (C16) originate from both sources.
      25.2
      Means within a row with different superscripts differ (P < 0.05).
      26.0
      Means within a row with different superscripts differ (P < 0.05).
      26.3
      Means within a row with different superscripts differ (P < 0.05).
      0.430.03
      ΣMixed27.4
      Means within a row with different superscripts differ (P < 0.05).
      28.3
      Means within a row with different superscripts differ (P < 0.05).
      30.0
      Means within a row with different superscripts differ (P < 0.05).
      0.929<0.001
      ΣPreformed41.5
      Means within a row with different superscripts differ (P < 0.05).
      40.0
      Means within a row with different superscripts differ (P < 0.05).
      37.6
      Means within a row with different superscripts differ (P < 0.05).
      0.898<0.001
      ΣOBCFA
      Odd- and branched-chain FA. Sum of C11:0, iso C13:0, anteiso C13:0, C13:0, iso C15:0, anteiso C15:0, C15:0, iso C16:0, iso C17:0, anteiso C17:0, C17:0, and C17:1 cis-9.
      3.62
      Means within a row with different superscripts differ (P < 0.05).
      3.43
      Means within a row with different superscripts differ (P < 0.05).
      3.78
      Means within a row with different superscripts differ (P < 0.05).
      0.0760.001
      a–c Means within a row with different superscripts differ (P < 0.05).
      1 Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      2 Main effect of treatment.
      3 De novo FA (<C16) are synthesized by the mammary gland; preformed FA (>C16) originate primarily from extraction from plasma; and mixed FA (C16) originate from both sources.
      4 Odd- and branched-chain FA. Sum of C11:0, iso C13:0, anteiso C13:0, C13:0, iso C15:0, anteiso C15:0, C15:0, iso C16:0, iso C17:0, anteiso C17:0, C17:0, and C17:1 cis-9.

      Enteric Gas Emissions

      Daily enteric CH4 emission was similar among diets, but cows fed CM had lower (P = 0.006) CH4 yield (i.e., CH4/kg DMI) than cows fed the ESBM and SSBM diets (Table 7). The CM diet had lower (P = 0.004) CH4 g/kg of digested OM in comparison with the SSBM diet. Methane emission intensity (i.e., CH4/kg of ECM milk) was similar among treatments. Hydrogen and CO2 emissions were not different among treatments.
      Table 7Enteric gas emissions in dairy cows fed diets containing canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM)
      ItemDietSEM
      Largest SEM published in table; n = 45 for all variables except CH4, g/kg of ECM, n = 44 (n represents the number of observations used in the statistical analysis). Data are presented as LSM.
      P-value
      Main effect of treatment.
      CMESBMSSBM
      CH4, g/d39641141417.20.46
      CH4, g/kg of DMI15.0
      Means within a row with different superscripts differ (P < 0.05).
      16.9
      Means within a row with different superscripts differ (P < 0.05).
      17.0
      Means within a row with different superscripts differ (P < 0.05).
      0.850.006
      CH4, g/kg of digested OM23.6
      Means within a row with different superscripts differ (P < 0.05).
      25.8
      Means within a row with different superscripts differ (P < 0.05).
      27.0
      Means within a row with different superscripts differ (P < 0.05).
      1.310.004
      CH4,
      Sjaunja et al. (1990).
      g/kg of ECM
      9.539.9410.40.600.18
      CO2, g/d13,11812,86813,1633390.38
      H2, g/d0.490.430.480.050.27
      a,b Means within a row with different superscripts differ (P < 0.05).
      1 Largest SEM published in table; n = 45 for all variables except CH4, g/kg of ECM, n = 44 (n represents the number of observations used in the statistical analysis). Data are presented as LSM.
      2 Main effect of treatment.
      3
      • Sjaunja L.O.
      • Baevre L.
      • Junkkarinen L.
      • Pedersen J.
      • Setälä J.
      A Nordic proposal for an energy corrected milk (ECM) formula.
      .

      Apparent Total-Tract Digestibility and Nitrogen Excretion

      Intake of all nutrients during the digestibility measurement periods was greater (P ≤ 0.004) for CM compared with ESBM and SSBM diets (Table 8). Apparent total-tract digestibility of DM, OM, and starch was lower (P ≤ 0.02) for SSBM in comparison with ESBM, but no differences between CM and SSBM diets were observed. The SSBM diet also had lower (P = 0.002) NDF digestibility than both CM and ESBM diets. The ESBM diet had the greatest (P < 0.001) CP digestibility and there was no difference in CP digestibility between CM and SSBM.
      Table 8Nutrient intake and apparent total-tract digestibility in dairy cows fed diets containing canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM)
      ItemDietSEM
      Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      P-value
      Main effect of treatment.
      CMESBMSSBM
      Intake,
      Intake during 3-d digestibility and urine data collection periods.
      kg/d
       DM26.8
      Means within a row with different superscripts differ (P < 0.05).
      24.6
      Means within a row with different superscripts differ (P < 0.05).
      24.3
      Means within a row with different superscripts differ (P < 0.05).
      0.84<0.001
       OM25.2
      Means within a row with different superscripts differ (P < 0.05).
      23.1
      Means within a row with different superscripts differ (P < 0.05).
      22.9
      Means within a row with different superscripts differ (P < 0.05).
      0.79<0.001
       NDF9.37
      Means within a row with different superscripts differ (P < 0.05).
      8.12
      Means within a row with different superscripts differ (P < 0.05).
      8.15
      Means within a row with different superscripts differ (P < 0.05).
      0.290<0.001
       ADF5.52
      Means within a row with different superscripts differ (P < 0.05).
      4.60
      Means within a row with different superscripts differ (P < 0.05).
      4.86
      Means within a row with different superscripts differ (P < 0.05).
      0.107<0.001
       CP4.34
      Means within a row with different superscripts differ (P < 0.05).
      4.08
      Means within a row with different superscripts differ (P < 0.05).
      4.03
      Means within a row with different superscripts differ (P < 0.05).
      0.1360.004
       Starch6.65
      Means within a row with different superscripts differ (P < 0.05).
      6.18
      Means within a row with different superscripts differ (P < 0.05).
      6.15
      Means within a row with different superscripts differ (P < 0.05).
      0.2100.001
      Apparent total-tract digestibility, %
       DM66.7
      Means within a row with different superscripts differ (P < 0.05).
      68.5
      Means within a row with different superscripts differ (P < 0.05).
      66.1
      Means within a row with different superscripts differ (P < 0.05).
      0.660.02
       OM67.9
      Means within a row with different superscripts differ (P < 0.05).
      69.5
      Means within a row with different superscripts differ (P < 0.05).
      67.0
      Means within a row with different superscripts differ (P < 0.05).
      0.640.02
       NDF48.0
      Means within a row with different superscripts differ (P < 0.05).
      47.2
      Means within a row with different superscripts differ (P < 0.05).
      43.9
      Means within a row with different superscripts differ (P < 0.05).
      1.070.002
       ADF41.140.442.41.540.58
       CP67.9
      Means within a row with different superscripts differ (P < 0.05).
      73.2
      Means within a row with different superscripts differ (P < 0.05).
      68.8
      Means within a row with different superscripts differ (P < 0.05).
      0.89<0.001
       Starch97.6
      Means within a row with different superscripts differ (P < 0.05).
      97.8
      Means within a row with different superscripts differ (P < 0.05).
      97.4
      Means within a row with different superscripts differ (P < 0.05).
      0.100.006
      a,b Means within a row with different superscripts differ (P < 0.05).
      1 Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      2 Main effect of treatment.
      3 Intake during 3-d digestibility and urine data collection periods.
      Nitrogen intake was greater (P = 0.002) for CM in comparison with SSBM and ESBM diets (Table 9). Daily fecal N excretion was greater (P < 0.001) for CM compared with the ESBM diet and tended (P = 0.09) to be greater for CM than the SSBM diet. However, fecal N excretion as % of N intake was similar between CM and SSBM and was lower (P = 0.001) for the ESBM diet. Diet had no effect on urinary N excretion, total excreta N, and milk N secretion; diets also had no effect on urinary excretion of purine derivatives. The ESBM diet had greater (P < 0.001) daily UUN excretion in comparison with both CM and SSBM, but UUN excretion as % of N intake was not different between ESBM and SSBM. Urinary creatinine concentration was greater (P = 0.003) and consequently estimated urine output was lower (P = 0.014) for CM, compared with the SBM diets.
      Table 9Nitrogen utilization and purine derivative (PD) excretion in dairy cows fed diets containing canola meal (CM), extruded soybean meal (ESBM), or solvent-extracted soybean meal (SSBM)
      ItemDietSEM
      Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      P-value
      Main effect of treatment.
      CMESBMSSBM
      N intake,
      Intake during 3-d digestibility and urine data collection periods.
      g/d
      699
      Means within a row with different superscripts differ (P < 0.05).
      672
      Means within a row with different superscripts differ (P < 0.05).
      650
      Means within a row with different superscripts differ (P < 0.05).
      21.10.002
      N excretion or secretion, g/d
       Urine N20423422016.30.24
       UUN
      UUN = urinary urea nitrogen.
      129
      Means within a row with different superscripts differ (P < 0.05).
      186
      Means within a row with different superscripts differ (P < 0.05).
      160
      Means within a row with different superscripts differ (P < 0.05).
      9.1<0.001
       Fecal N223
      Means within a row with different superscripts differ (P < 0.05).
      175
      Means within a row with different superscripts differ (P < 0.05).
      203
      Means within a row with different superscripts differ (P < 0.05).
      10.6<0.001
       Total excreta N42741042320.40.67
       Milk N21320721112.10.82
      As % of N intake
       Urine N29.835.034.12.140.17
       UUN18.8
      Means within a row with different superscripts differ (P < 0.05).
      27.8
      Means within a row with different superscripts differ (P < 0.05).
      24.8
      Means within a row with different superscripts differ (P < 0.05).
      1.14<0.001
       Fecal N32.0
      Means within a row with different superscripts differ (P < 0.05).
      26.1
      Means within a row with different superscripts differ (P < 0.05).
      31.0
      Means within a row with different superscripts differ (P < 0.05).
      1.060.001
       Total excreta N61.861.165.22.470.45
       Milk N30.830.932.61.230.42
      Urine output, kg/d20.5
      Means within a row with different superscripts differ (P < 0.05).
      24.5
      Means within a row with different superscripts differ (P < 0.05).
      24.0
      Means within a row with different superscripts differ (P < 0.05).
      1.520.003
      Urinary PD excretion, mmol/d
       Allantoin65770171276.30.86
       Uric acid77.377.678.06.320.99
       Total PD80986287591.60.85
      Creatinine, mg/L885
      Means within a row with different superscripts differ (P < 0.05).
      730
      Means within a row with different superscripts differ (P < 0.05).
      774
      Means within a row with different superscripts differ (P < 0.05).
      56.90.003
      a–c Means within a row with different superscripts differ (P < 0.05).
      1 Largest SEM published in table; n = 45 (n represents number of observations used in the statistical analysis). Data are presented as LSM.
      2 Main effect of treatment.
      3 Intake during 3-d digestibility and urine data collection periods.
      4 UUN = urinary urea nitrogen.

      DISCUSSION

      Diet and Feed Composition

      The diets used in this study were formulated based on
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      . The discrepancy between analyzed RDP and RUP of CM (this study and
      • Maxin G.
      • Ouellet D.R.
      • Lapierre H.
      Ruminal degradability of dry matter, crude protein, and amino acids in soybean meal, canola meal, corn, and wheat dried distillers grains.
      ) and book values (i.e.,
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      ) suggests that some nutritional models likely underestimates MP supply when CM is fed to lactating dairy cows. The
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      dairy model, for example, uses 36.7% RUP (CP basis) for mechanically extracted CM versus 43% to 48% for SSBM, when DMI is at 4% of BW and the diet is 50% forages. Analyzed RUP in the current experiment, however, was 63.2% versus 49.2% for the 2 meals, respectively. The more recent beef
      • NRC (National Research Council)
      Nutrient Requirements of Beef Cattle.
      model ranks RUP of CM higher than that of high-protein SSBM (42.3 versus 29.5%, respectively), which is in the same direction as analyzed data from the current experiment. In contrast, the latest Institut National de la Recherche Agronomique model (
      • Nozière P.
      • Sauvant D.
      • Delaby L.
      INRA Feeding System for Ruminants.
      ) uses rumen ED of N (calculated at 6%/h passage rate) of 69 and 63% for rapeseed meal and 48% CP SBM (both <5% oil), respectively, which is considerably different from in situ ED of CP determined in the current study (36.7% and 50.6%, respectively, estimated at the same, 6%/h, rate of passage). It is noted that the RUP values for CM estimated in the current experiment are higher than reported by others (e.g.,
      • Maxin G.
      • Ouellet D.R.
      • Lapierre H.
      Ruminal degradability of dry matter, crude protein, and amino acids in soybean meal, canola meal, corn, and wheat dried distillers grains.
      ;
      • Broderick G.A.
      • Colombini S.
      • Costa S.
      • Karsli M.A.
      • Faciola A.P.
      Chemical and ruminal in vitro evaluation of Canadian canola meals produced over 4 years.
      ) and may be specific to the particular batch of CM used in the experiment.
      These discrepancies in RUP estimates among nutritional models and analyzed samples can be partially related to variations in the composition of oilseed meals due to cultivar, environmental conditions during growth and harvest, and meal processing (
      • Paula E.M.
      • Monteiro H.F.
      • Silva L.G.
      • Benedeti P.D.B.
      • Daniel J.L.P.
      • Shenkoru T.
      • Broderick G.A.
      • Faciola A.P.
      Effects of replacing soybean meal with canola meal differing in rumen-undegradable protein content on ruminal fermentation and gas production kinetics using 2 in vitro systems.
      ), but will also depend on the analytical procedures used. In the case of CM, the process of oil extraction from canola seeds is likely also a factor contributing to the higher analyzed versus
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      values for RUP. Because canola seeds have greater oil content than soybeans (approximately 42 versus 19%, respectively;
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      ), canola requires an extra step to extract the oil from the seeds: first the seeds go through an extrusion process to reduce the oil content to around 18%, after which the meal is subjected to solvent extraction (). Oil from soybeans is directly extracted with solvent (to produce SSBM) because of their lower oil content. Mechanical extraction, or extrusion, generates heat which decreases ruminal protein degradability and increases RUP content of the meal (
      • Björck I.
      • Asp N.G.
      The effects of extrusion cooking on nutritional value—A literature review.
      ;
      • Giallongo F.
      • Oh J.
      • Frederick T.
      • Isenberg B.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Extruded soybean meal increased feed intake and milk production in dairy cows.
      ). As a result CM had a RUP value similar to that of ESBM in the current experiment.
      In the present experiment, diets were initially, before the experiment began, formulated using
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      feed library values for protein fractions for all feed ingredients. However, values presented in Table 1 were derived based on analyzed ingredient composition at the end of the experiment and using values from the conducted in situ experiment for the protein meals. Greater RUP values, lower degradation rates of fraction b CP, and lower ED of the meals in comparison with
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      library values resulted in differences between predicted and actual RDP and digestible Met supply in all 3 diets. Although the reconstituted diets suggested deficiencies (based on
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      ) in RDP supply, MUN values for all 3 diets (average of 10.5 ± 0.40 mg/dL) were within the range considered optimal for Holstein cows (i.e., 8 to 12 mg/dL;
      • Kohn R.A.
      • Kalscheur K.F.
      • Russek-Cohen E.
      Evaluation of models to estimate urinary nitrogen and expected milk urea nitrogen.
      ), suggesting positive ruminal CP balance. It has been discussed in the literature that
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      may overpredict RUP supply (
      • Broderick G.A.
      • Huhtanen P.
      • Ahvenjarvi S.
      • Reynal S.
      • Shingfield K.
      Quantifying ruminal nitrogen metabolism using the omasal sampling technique in cattle—A meta-analysis.
      ;
      • White R.R.
      • Roman-Garcia Y.
      • Firkins J.L.
      • Kononoff P.
      • VandeHaar M.J.
      • Tran H.
      • McGill T.
      • Garnett R.
      • Hanigan M.D.
      Evaluation of the National Research Council (2001) dairy model and derivation of new prediction equations. 2. Rumen degradable and undegradable protein.
      ), thus underestimating RDP supply in some dietary situations (
      • Cyriac J.
      • Rius A.G.
      • McGilliard M.L.
      • Pearson R.E.
      • Bequette B.J.
      • Hanigan M.D.
      Lactation performance of mid-lactation dairy cows fed ruminally degradable protein at concentrations lower than National Research Council recommendations.
      ). The in situ technique is the standard technique to predict protein degradability of feedstuffs; however, predictions of kp and kd appear to be biased in the current
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      system, resulting in discrepancies between predicted and observed production responses (
      • White R.R.
      • Roman-Garcia Y.
      • Firkins J.L.
      • Kononoff P.
      • VandeHaar M.J.
      • Tran H.
      • McGill T.
      • Garnett R.
      • Hanigan M.D.
      Evaluation of the National Research Council (2001) dairy model and derivation of new prediction equations. 2. Rumen degradable and undegradable protein.
      ). Rumen-protected Met was supplemented to all diets in an attempt to meet
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      recommendations for digestible Met supply. Differences between initially formulated and reconstituted diet composition, however, resulted in digestible Met deficiencies for all 3 diets, with the ESBM diet having the largest deficiency (0.27 percentage units; intended versus observed Met supply).

      Feed Intake and Milk Production and Composition

      Increased DMI when CM replaces SSBM has been previously reported (meta-analyses by
      • Huhtanen P.
      • Hetta M.
      • Swensson C.
      Evaluation of canola meal as a protein supplement for dairy cows: A review and a meta-analysis.
      ;
      • Martineau R.
      • Ouellet D.R.
      • Lapierre H.
      Feeding canola meal to dairy cows: A meta-analysis on lactational responses.
      ). It is speculated that the increased DMI in cows fed CM is due to better supply of EAA (i.e., Met), that can potentially enhance MY, and as a consequence, cows would need to increase their DMI to support the increased energy demand of the mammary gland (
      • Huhtanen P.
      • Hetta M.
      • Swensson C.
      Evaluation of canola meal as a protein supplement for dairy cows: A review and a meta-analysis.
      ).
      • Paula E.M.
      • Broderick G.A.
      • Faciola A.P.
      Effects of replacing soybean meal with canola meal for lactating dairy cows fed 3 different ratios of alfalfa to corn silage.
      reported increased MY when CM replaced SSBM, but no effect on DMI was observed.
      • Shingfield K.J.
      • Vanhatalo A.
      • Huhtanen P.
      Comparison of heat-treated rapeseed expeller and solvent-extracted soya-bean meal as protein supplements for dairy cows given grass silage-based diets.
      also observed marginal responses in milk and ECM yields when heat-treated rapeseed expeller meal replaced SBM with no effects on DMI. In contrast, other studies observed a lack of effect of CM on both DMI and cow performance (
      • Paula E.M.
      • Broderick G.A.
      • Danes M.A.C.
      • Lobos N.E.
      • Zanton G.I.
      • Faciola A.P.
      Effects of replacing soybean meal with canola meal or treated canola meal on ruminal digestion, omasal nutrient flow, and performance in lactating dairy cows.
      ;
      • Toti J.
      • Ghasemi E.
      • Khorvash M.
      Effects of replacing soybean meal with canola meal and decreasing crude protein on milk production and nutrient utilization of dairy cows in early lactation.
      ). In the current experiment, the effect of CM on MY was clearly a result of increased DMI, because feed efficiency was similar among diets, which is in agreement with data from
      • Pereira A.B.D.
      • Moura D.C.
      • Whitehouse N.L.
      • Brito A.F.
      Production and nitrogen metabolism in lactating dairy cows fed finely ground field pea plus soybean meal or canola meal with or without rumen-protected methionine supplementation.
      . Increased DMI with the CM diet observed in the current experiment could be partially attributed to differences in the energy density of the diets. Greater DMI was reported when cereal grains were replaced with fibrous by-products (
      • Huhtanen P.
      • Rinne M.
      • Nousiainen J.
      Evaluation of concentrate factors affecting silage intake of dairy cows: A development of the relative total diet intake index.
      ), which was attributed to lower energy density of the latter. In the present experiment, the CM diet, due to its higher fiber content, had an estimated NEL concentration of 1.54 Mcal/kg DM, compared with 1.58 Mcal/kg DM for the SBM diets. Because cows had the same ECM production, lower energy density may have been compensated by greater DMI for the CM diet. The greater intake for the CM diet may be also partially related to greater hay-straw inclusion in the SBM diets (23.5 versus 25.8% in CM and SBM diets, respectively). Rates of passage of forage fiber sources are likely slower than those of nonforage sources (
      • Firkins J.L.
      Effects of feeding nonforage fiber sources on site of fiber digestion.
      ), which may have influenced rumen fill and therefore DMI.
      In the case of ESBM versus SSBM, the difference in MY in the current experiment was partially a result of the numerical increase in DMI by the former diet, likely in addition to its greater RUP content. In our previous studies with ESBM we reported increased DMI (compared with SSBM) in mid-lactation (
      • Giallongo F.
      • Oh J.
      • Frederick T.
      • Isenberg B.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Extruded soybean meal increased feed intake and milk production in dairy cows.
      ), but not in early-lactation cows (
      • Harper M.T.
      • Oh J.
      • Melgar A.
      • Nedelkov K.
      • Räisänen S.
      • Chen X.
      • Martins C.M.M.R.
      • Young M.
      • Ott T.L.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Production effects of feeding extruded soybean meal to early-lactation dairy cows.
      ). Diets containing ESBM were also reported to increase MY when replacing SSBM, but no differences in milk components or feed efficiency were observed (
      • Giallongo F.
      • Oh J.
      • Frederick T.
      • Isenberg B.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Extruded soybean meal increased feed intake and milk production in dairy cows.
      ), which is in agreement with responses in the current experiment. In the meta-analysis by
      • Huhtanen P.
      • Hetta M.
      • Swensson C.
      Evaluation of canola meal as a protein supplement for dairy cows: A review and a meta-analysis.
      , milk protein yield was increased by CM compared with SBM, which was a result of increased DMI and consequently MY because milk protein concentration was not affected. Similar results were reported in the meta-analysis by
      • Martineau R.
      • Ouellet D.R.
      • Lapierre H.
      Feeding canola meal to dairy cows: A meta-analysis on lactational responses.
      , which is in agreement with data from the current experiment.
      Lower MUN concentration in dairy cows fed CM compared with cows fed SSBM is typically reported in the literature (
      • Paula E.M.
      • Broderick G.A.
      • Danes M.A.C.
      • Lobos N.E.
      • Zanton G.I.
      • Faciola A.P.
      Effects of replacing soybean meal with canola meal or treated canola meal on ruminal digestion, omasal nutrient flow, and performance in lactating dairy cows.
      ,
      • Paula E.M.
      • Broderick G.A.
      • Faciola A.P.
      Effects of replacing soybean meal with canola meal for lactating dairy cows fed 3 different ratios of alfalfa to corn silage.
      ;
      • Pereira A.B.D.
      • Moura D.C.
      • Whitehouse N.L.
      • Brito A.F.
      Production and nitrogen metabolism in lactating dairy cows fed finely ground field pea plus soybean meal or canola meal with or without rumen-protected methionine supplementation.
      ) and is consistent with results from the current experiment. This effect is attributed to lower ruminal protein degradation of CM compared with SSBM (
      • Maxin G.
      • Ouellet D.R.
      • Lapierre H.
      Effect of substitution of soybean meal by canola meal or distillers grains in dairy rations on amino acid and glucose availability.
      ), and possibly a better utilization of AA absorbed postruminally in CM-fed cows (
      • Martineau R.
      • Ouellet D.R.
      • Lapierre H.
      The effect of feeding canola meal on concentrations of plasma amino acids.
      ). The increased plasma urea concentration with the SBM diets, compared with CM, agrees with the MUN data in the current study. These results can be partially attributed to the lower intestinal N digestibility (analyzed using a 3-step in vitro technique) of CM, compared with the other treatments. Compared with the other diets, ESBM had a greater digestible RUP supply, which was not accompanied by greater milk protein synthesis, thus likely resulting in increased AA catabolism (
      • Nousiainen J.
      • Shingfield K.J.
      • Huhtanen P.
      Evaluation of milk urea nitrogen as a diagnostic of protein feeding.
      ) and consequently MUN concentration. In addition, reviews by
      • Santos F.A.P.
      • Santos J.E.P.
      • Theurer C.B.
      • Huber J.T.
      Effects of rumen-undegradable protein on dairy cow performance: A 12-year literature review.
      and
      • Ipharraguerre I.R.
      • Clark J.H.
      Impacts of the source and amount of crude protein on the intestinal supply of nitrogen fractions and performance of dairy cows.
      suggested that microbial efficiency may decrease with increased RUP supply, which could have also contributed to greater MUN values in the ESBM diet. The greater MUN in SSBM compared with CM diet is likely related to greater RDP supply with the former diet.

      Plasma Amino Acids Concentrations

      Compared with ESBM, the CM diet had lower total-tract CP digestibility and, accordingly, higher fecal N excretion and lower plasma EAA concentrations. Diets were formulated to provide a similar amount of digestible Met; however, as discussed earlier, differences between formulated and reconstituted diets resulted in different Met supply. The ESBM diet had the largest deficiency in estimated Met supply, as well as the lowest Met plasma concentration. Concentration of an EAA in peripheral blood plasma reflects its absorption and use; hence, if the concentration of an EAA is decreased, it can be considered to be limiting in the diet (
      • Broderick G.A.
      • Satter L.D.
      • Harper A.E.
      Use of plasma amino acid concentration to identify limiting amino acids for milk production.
      ). Further, EAA that are not required by the mammary gland return to peripheral circulation (
      • Arriolo Apelo S.I.
      • Knapp J.R.
      • Hanigan M.D.
      Invited review: Current representation and future trends of predicting amino acid utilization in the lactating dairy cow.
      ). Because all 3 diets resulted in similar ECM and milk protein yields in the current experiment, it is likely that greater plasma Met concentration in CM and SSBM, in comparison with ESBM diet, was a result of greater supply of Met that did not result in greater milk protein synthesis. The efficiency of conversion of metabolizable AA into milk protein is not constant among individual AA and varies according to metabolizable AA supply and demand (
      • Doepel L.
      • Pacheco D.
      • Kennelly J.J.
      • Hanigan M.D.
      • Lopez I.F.
      • Lapierre H.
      Milk protein synthesis as a function of amino acid supply.
      ). This phenomenon may explain why the CM and SSBM diet did not improve milk protein production, in spite of greater plasma Met concentrations compared with the ESBM diet.
      Interestingly, plasma concentration of 1-methylhistidine was decreased by SSBM, compared with the other 2 diets. This response was similar to that observed in a previous experiment (
      • Giallongo F.
      • Oh J.
      • Frederick T.
      • Isenberg B.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Extruded soybean meal increased feed intake and milk production in dairy cows.
      ), where concentration of plasma 1-methylhistidine was lower for SSBM compared with ESBM processed at 171°C. The mechanism behind this effect is not clear. It is reported that anserine (β-alanyl-1-methyll-histidine) is the precursor of 1-methylhistidine, but it is unknown how hydrolysis of anserine and the subsequent appearance of 1-methylhistidine in blood and urine are regulated in cattle (
      • Houweling M.
      • Van Der Drift S.G.A.
      • Jorritsma R.
      • Tielens A.G.M.
      Quantification of plasma 1-and 3-methylhistidine in dairy cows by high-performance liquid chromatography–tandem mass spectrometry.
      ).

      Milk Fatty Acid Proportions

      No differences in milk fat concentration nor yield were observed among diets in the current experiment. However, milk FA composition was clearly altered by the type of protein meal and supplemental oil. It is well documented that the FA profile of milk can be modified by dietary factors (
      • Sutton J.D.
      Altering milk composition by feeding.
      ;
      • Jenkins T.C.
      • McGuire M.A.
      Major advances in nutrition: Impact on milk composition.
      ). The increased concentration of 18:1, 20:0, and MUFA with CM, compared with the ESBM and SSBM diets, is in agreement with previous reports in which canola oil was added to the diet of lactating cows (
      • DePeters E.J.
      • German J.B.
      • Taylor S.J.
      • Essex S.T.
      • Perez-Monti H.
      Fatty acid and triglyceride composition of milk fat from lactating Holstein cows in response to supplemental canola oil.
      ;
      • Hristov A.N.
      • Domitrovich C.
      • Wachter A.
      • Cassidy T.
      • Lee C.
      • Shingfield K.J.
      • Kairenius P.
      • Davis J.
      • Brown J.
      Effect of replacing solvent-extracted canola meal with high-oil traditional canola, high-oleic acid canola, or high-erucic acid rapeseed meals on rumen fermentation, digestibility, milk production, and milk fatty acid composition in lactating dairy cows.
      ). Similarly,
      • Lopes J.C.
      • Harper M.T.
      • Giallongo F.
      • Oh J.
      • Smith L.
      • Ortega-Perez A.M.
      • Harper S.A.
      • Melgar A.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Effect of high-oleic-acid soybeans on production performance, milk fatty acid composition, and enteric methane emission in dairy cows.
      observed increased PUFA concentration in milk fat from cows fed conventional ESBM compared with milk from cows fed high-oleic ESBM or whole roasted soybeans.

      Enteric Gas Emissions

      Treatment did not affect daily enteric CH4 emission in the current experiment, but cows fed CM produced less enteric CH4 per kg of DMI (i.e., CH4 yield) in comparison with both ESBM and SSBM.
      • Gidlund H.
      • Hetta M.
      • Krizsan S.J.
      • Lemosquet S.
      • Huhtanen P.
      Effects of soybean meal or canola meal on milk production and methane emissions in lactating dairy cows fed grass silage-based diets.
      observed a numerical trend for decreased CH4 yield in diets with inclusion of heat-treated CM compared with SSBM and associated this reduction to lower CP degradability of the heat-treated CM, which reduced availability of fermentable substrate in the rumen. The decreased CH4 yield with the CM diet in the current experiment was most likely a result of similar daily CH4 emission and increased DMI compared with ESBM and SSBM diets. The increase in DMI by CM, however, did not produce a significant effect on ECM and, therefore, CH4 emission intensity was not affected.

      Apparent Total-Tract Digestibility and Nitrogen Utilization

      • Paula E.M.
      • Broderick G.A.
      • Danes M.A.C.
      • Lobos N.E.
      • Zanton G.I.
      • Faciola A.P.
      Effects of replacing soybean meal with canola meal or treated canola meal on ruminal digestion, omasal nutrient flow, and performance in lactating dairy cows.
      reported lower DM, OM, NDF, and CP digestibilities in diets in which SSBM was substituted by CM. Other studies reported similar (
      • Brito A.F.
      • Broderick G.A.
      Effects of different protein supplements on milk production and nutrient utilization in lactating dairy cows.
      ;
      • Huhtanen P.
      • Hetta M.
      • Swensson C.
      Evaluation of canola meal as a protein supplement for dairy cows: A review and a meta-analysis.
      ) or decreased (
      • Pereira A.B.D.
      • Moura D.C.
      • Whitehouse N.L.
      • Brito A.F.
      Production and nitrogen metabolism in lactating dairy cows fed finely ground field pea plus soybean meal or canola meal with or without rumen-protected methionine supplementation.
      ) DM, OM, and CP digestibilities for CM in comparison with SSBM diets. In our previous studies with ESBM we did not observe differences in apparent digestibility of any nutrient between ESBM (171°C extrusion temperature, as in the present experiment) and SSBM diets (
      • Giallongo F.
      • Oh J.
      • Frederick T.
      • Isenberg B.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Extruded soybean meal increased feed intake and milk production in dairy cows.
      ;
      • Harper M.T.
      • Oh J.
      • Melgar A.
      • Nedelkov K.
      • Räisänen S.
      • Chen X.
      • Martins C.M.M.R.
      • Young M.
      • Ott T.L.
      • Kniffen D.M.
      • Fabin R.A.
      • Hristov A.N.
      Production effects of feeding extruded soybean meal to early-lactation dairy cows.
      ). The statistically significant effect of treatment on DM, OM, and starch digestibility in the current experiment was caused by differences between ESBM and SSBM, but digestibility of these nutrients for both diets was similar to that of CM.
      The ESBM meal had the greatest (in vitro) intestinal digestibility of CP, which may explain the observed greater CP apparent digestibility of the ESBM diet in comparison with both CM and SSBM diets in the current experiment. However, it is not clear why the SSBM diet had lower NDF digestibility than the CM and ESBM diets. As discussed before, the CM diet had lower portion of NDF coming from forage due to lower hay/straw inclusion compared with the SBM diets. Nonforage fiber sources have lower iNDF fraction compared with forages (
      • Bhatti S.A.
      • Firkins J.L.
      Kinetics of hydration and functional specific gravity of fibrous feed by-products.
      ), which may have affected NDF digestibility in the SSBM diet, compared with CM. This hypothesis, however, disagrees with the lack of difference in NDF digestibility between the CM and ESBM diets; therefore, it is unlikely that the difference in hay/straw inclusion is the reason for lower nutrient digestibilities in the SSBM diet. Although differences in FA profile among diets exist, the free oil inclusion in the SSBM diet was less than 1% of DM and it is unlikely to have affected fiber degradability.
      Urinary creatinine concentration in the current study was lower for the SBM diets, compared with CM and, as a result, estimated urine output was greater for the former diets. Daily creatinine production and consequently creatinine excretion are related to muscle mass and are therefore proportional to the animal's BW (
      • Hobson W.
      Urinary output of creatine and creatinine associated with physical exercise, and its relationship to carbohydrate metabolism.
      ;
      • Lofgreen G.P.
      • Garrett W.N.
      Creatinine excretion and specific gravity as related to the composition of the 9, 10, 11th rib cut of Hereford steers.
      ) and are little affected by dietary factors (
      • Chizzotti M.L.
      • de Campos Valadares Filho S.
      • Valadares R.F.D.
      • Chizzotti F.H.M.
      • Tedeschi L.O.
      Determination of creatinine excretion and evaluation of spot urine sampling in Holstein cattle.
      ). On the other hand, urine volume can be affected by N excretion as urine osmolality is kept constant (
      • Bannink A.
      • Valk H.
      • Van Vuuren A.M.
      Intake and excretion of sodium, potassium, and nitrogen and the effects on urine production by lactating dairy cows.
      ). It appears that greater osmotic pressure due to greater plasma urea N concentration with the SBM diets increased the water volume necessary for UUN excretion, resulting in greater urine volume, and by dilution, lower creatinine concentration in spot urine samples. The increased urinary urea excretion for the SBM diets is in agreement with the greater plasma urea and MUN concentrations with these diets compared with CM.

      CONCLUSIONS

      In this experiment, RUP content of CM was similar to that of ESBM and considerably greater than RUP of SSBM and
      • NRC (National Research Council)
      Nutrient Requirements of Dairy Cattle.
      values for CM. This is likely due to heat generated during the extrusion process of CM before solvent extraction. Although CM increased DMI, treatments had no effect on milk components and ECM yield or ECM feed efficiency. Cows fed CM produced less enteric CH4 per kg of DMI, but had similar CH4 emission intensity, compared with cows fed the SBM diets, which was a result of the greater DMI and similar ECM yield with the former diet. Overall, data suggest that CM may enhance DMI, but dairy cows fed CM, SSBM, or ESBM, on an equal CP basis, have similar performance in terms of ECM, component yields, and feed efficiency.

      ACKNOWLEDGMENTS

      This work was supported by the USDA (Washington, DC) National Institute of Food and Agriculture Federal Appropriations under Project PEN 04539 and Accession Number 1000803. The project was partially supported by funds from the Pennsylvania Soybean Board (Agreement R2012008). The authors thank Fabin Bros. Farms (Indiana, PA) for providing the extruded soybean meal for the experiment. The authors also thank the staff of The Pennsylvania State University Dairy Teaching and Research Center (University Park) for their conscientious care and management of the animals and for technical assistance during the study. There is no conflict of interest to state.

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