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Supplementing different ratios of short- and medium-chain fatty acids to long-chain fatty acids in dairy cows: Changes of milk fat production and milk fatty acids composition

  • Author Footnotes
    1 Y. Sun and D. P. Bu contributed equally to this research.
    Y. Sun
    Footnotes
    1 Y. Sun and D. P. Bu contributed equally to this research.
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • Author Footnotes
    1 Y. Sun and D. P. Bu contributed equally to this research.
    D.P. Bu
    Footnotes
    1 Y. Sun and D. P. Bu contributed equally to this research.
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • J.Q. Wang
    Correspondence
    Corresponding author:
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • H. Cui
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • X.W. Zhao
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • X.Y. Xu
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • P. Sun
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • L.Y. Zhou
    Affiliations
    State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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  • Author Footnotes
    1 Y. Sun and D. P. Bu contributed equally to this research.
Open ArchivePublished:February 18, 2013DOI:https://doi.org/10.3168/jds.2012-5356

      Abstract

      Milk fat synthesis might be promoted by the dietary addition of long-chain fatty acids (LCFA) or short- and medium-chain fatty acids (SMCFA). This study evaluated unprotected lipid supplementation with different ratios of SMCFA to LCFA, which had equivalent fatty acid (FA) proportions (by weight) to those in milk, on milk fat production and milk FA composition. Thirty-six Holstein cows (183 ± 46 d in milk) were divided into 3 treatments according to a randomized block design. Cows in 3 treatments received supplements of 80 g/d of SMCFA mixture and 320 g/d of LCFA mixture (ratio of SMCFA to LCFA was 20:80); 400 g/d of butterfat (ratio of SMCFA to LCFA was 40:60); or 240 g/d of SMCFA mixture and 160 g/d of LCFA mixture (ratio of SMCFA to LCFA was 60:40). The FA compositions of the SMCFA mixture and the LCFA mixture were similar to the de novo synthesized FA (except C4:0) and preformed FA (except trans FA) found in the butterfat, respectively. Fatty acid supplements and butterfat were consumed by cows daily before the morning feeding during the 8-wk experimental period. Dry matter intake and milk yield were not different among the treatments. The milk fat percentage and total SMCFA concentration in milk fat tended to increase linearly and the proportion of milk total solids increased linearly with increasing ratios of SMCFA to LCFA in the supplements, whereas milk fat yield was not changed. We suggest that increasing ratios of SMCFA to LCFA in diets has the potential to improve milk fat synthesis.

      Key words

      Introduction

      Milk fat, which represents the major economic value of milk, is the substantial component contributing to the energy density of whole milk and dairy products and accounts for many of their physical properties, processing attributes, and organoleptic qualities (
      • Harvatine K.J.
      • Boisclair Y.R.
      • Bauman D.E.
      Recent advances in the regulation of milk fat synthesis.
      ). Compared with other solid components in milk, fat concentration is the most sensitive to the dietary influences (
      • Sutton J.A.
      Altering milk composition by feeding.
      ). The effect of dairy cow nutrition on milk fat composition and yield has been reviewed extensively (
      • Lock A.L.
      • Bauman D.E.
      Modifying milk fat composition of dairy cows to enhance fatty acids beneficial to human health.
      ; emsp
      • Jenkins T.C.
      • McGuire M.A.
      Major advances in nutrition: Impact on milk composition.
      ; emsp
      • Harvatine K.J.
      • Boisclair Y.R.
      • Bauman D.E.
      Recent advances in the regulation of milk fat synthesis.
      ). But the studies that demonstrated consistent ways to increase milk fat concentration are limited.
      The addition of saturated long-chain fatty acids (LCFA) tended to increase milk fat yield (
      • Steele W.
      • Moore J.H.
      The effect of a series of saturated fatty acids in the diet on milk-fat secretion in the cow.
      ; emsp
      • Drackley J.K.
      • Klusmeyer T.H.
      • Trusk A.M.
      • Clark J.H.
      Infusion of long-chain fatty acids varying in saturation and chain length into the abomasums of lactating dairy cows.
      ), but the de novo synthesis of short- and medium-chain fatty acids (SMCFA) by mammary gland cells was inhibited by the exogenous LCFA (
      • Hansen H.O.
      • Knudsen J.
      Effect of exogenous long-chain fatty acids on lipid biosynthesis in dispersed ruminant mammary gland epithelial cells: Esterification of long-chain exogenous fatty acid.
      ,
      • Hansen H.O.
      • Knudsen J.
      Effect of exogenous long-chain fatty acids on individual fatty acid synthesis by dispersed ruminant mammary gland cells.
      ). The SMCFA (C4–C14) and about half of C16, which form de novo from circulating acetate and BHBA in the mammary gland, make up 40% of all the milk FA (
      • Chilliard Y.
      • Ferlay A.
      • Mansbridge R.M.
      • Doreau M.
      Ruminant milk fat plasticity: Nutritional control of saturated, polyunsaturated, trans and conjugated fatty acids.
      ); LCFA (the carbon chain length >C16) along with the other half of C16, which originate from feed and body adipose tissues (
      • Mansbridge R.J.
      • Blake J.S.
      Nutritional factors affecting the fatty acid composition of bovine milk.
      ; emsp
      • Kalač P.
      • Samková E.
      The effect of feeding various forages on fatty acid composition of bovine milk fat: A review.
      ), comprise 60% of all FA in the milk (
      • Chilliard Y.
      • Ferlay A.
      • Mansbridge R.M.
      • Doreau M.
      Ruminant milk fat plasticity: Nutritional control of saturated, polyunsaturated, trans and conjugated fatty acids.
      ).
      • Steele W.
      • Moore J.H.
      The effect of a series of saturated fatty acids in the diet on milk-fat secretion in the cow.
      reported that the milk fat percentage was increased when myristic acid and palmitic acid were supplemented to the diet of lactating cows. Researchers inferred that the provision of SMCFA via dietary means might enhance milk fat content (
      • Kadegowda A.K.G.
      • Plperova L.S.
      • Delmonte P.
      • Erdman R.A.
      Abomasal infusion of butterfat increases milk fat in lactating dairy cows.
      ; emsp
      • Vyas D.
      • Teter B.B.
      • Erdman R.A.
      Milk fat responses to dietary short and medium chain fatty acids in lactating dairy cows.
      ).
      • Kadegowda A.K.G.
      • Plperova L.S.
      • Delmonte P.
      • Erdman R.A.
      Abomasal infusion of butterfat increases milk fat in lactating dairy cows.
      reported abomasal infusion of butterfat—containing both SMCFA and LCFA with FA composition identical to that of milk—increased milk fat percentage and yield, whereas infusion of only the LCFA present in the butterfat had no effect.
      Thus, we hypothesized that unprotected fat supplements with different ratios of SMCFA to LCFA would have diverse influences on milk fat production, and milk fat synthesis might be promoted. In this study, the effect of different ratios of SMCFA to LCFA (20:80, 40:60, and 60:40) on milk fat synthesis and milk FA composition was evaluated.

      Materials and methods

      Experimental Design and Treatments

      The present study was performed at Beijing Cangdafu Dairy Farm (Beijing, China). Animals were cared for in accordance with the guidelines established by the Institute of Animal Science, Chinese Academy of Agriculture Science, Beijing, China.
      Thirty-six lactating Holstein cows were blocked by average daily milk yield, DIM, and parity (183 ± 46, 21 ± 3.37 kg/d, and 1.83 ± 1.25, respectively) and then randomly assigned to 1 of 3 treatments, each treatment consisting of 12 cows. Treatment supplements were added to diets as follows: (1) 80 g/d of SMCFA mixture and 320 g/d of LCFA mixture (20SM80L; ratio of SMCFA to LCFA was 20:80); (2) 400 g/d of butterfat (40SM60L: ratio of SMCFA to LCFA was 40:60); or (3) 240 g/d of SMCFA mixture and 160 g/d of LCFA mixture (60SM40L; ratio of SMCFA to LCFA was 60:40). The FA compositions of the 3 treatment supplements are presented in Table 1. Except for butyrate in the SMCFA and trans FA in the LCFA, the FA compositions of the SMCFA mixture and LCFA mixture were similar to the FA derived from de novo synthesis and preformed FA in butterfat (Bright Dairy Co., Shanghai, China), which contain all FA with composition identical to milk. Because the amount of trans-10,cis-12 conjugated linoleic acid (CLA) in butterfat is less than the effective dose for milk fat depression (
      • Peterson D.G.
      • Baumgard L.H.
      • Bauman D.E.
      Short communication: Milk fat response to low doses of trans-10, cis-12 conjugated linoleic acid (CLA).
      ), the inhibitory effect of trans-10,cis-12 CLA in the butterfat was neglected. The SMCFA mixture included 6% caproic acid (C6:0), 4% caprylic acid (C8:0), 9% capric acid (C10:0), 10% lauric acid (C12:0), 32% myristic acid (C14:0) and 39% palmitic acid (C16:0; Guanhua Co. Ltd., Nanjing, China). The LCFA mixture included 59% cocoa butter (major FA by weight percentage were C12:0, 1.25%; C16:0, 24.64%; C18:0, 35.55%; cis-9 C18:1, 32.91%; C18:2, 3.45%; Linzhishanyang Co. Ltd., Jiangsu, China), 16% olive oil (major FA by weight percentage were: C16:0, 9.43%; C18:0, 2.86%; cis-9 C18:1, 72.81%; C18:2, 12.20%; Shijikangxin Ltd., Beijing, China), and 25% palm oil (major FA by weight percentage were: C16:0, 47.12%; C18:0, 4.69%; cis-9 C18:1, 37.39%; C18:2, 9.67%; Yihai Ltd., Shanghai, China).
      Table 1Fatty acid composition of FA supplements in treatments.
      FA
      Expressed as numbers of carbons:numbers of double bonds.
      Treatment,
      20SM80L=supplemented with 400g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L=supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L=supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      g/100 g of total FA
      20SM80L40SM60L60SM40L
      4:00.003.920.00
      6:01.232.283.71
      8:00.811.342.35
      10:01.803.275.36
      12:02.683.756.61
      14:06.5011.0818.62
      14:10.001.530.00
      15:00.001.180.00
      16:030.0528.8233.37
      16:10.251.290.32
      17:00.140.570.07
      18:018.1810.859.08
      cis-9 18:132.4420.9816.82
      trans-11 18:10.033.350.02
      Conjugated linoleic acid0.111.720.06
      18:25.142.533.30
      18:30.260.880.13
      20:00.370.250.19
      cis-8,11,14 20:30.000.010.00
      cis-11,14,17 20:30.000.170.00
      Others00.220
      1 Expressed as numbers of carbons:numbers of double bonds.
      2 20SM80L = supplemented with 400 g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L = supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L = supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      Because about half of the C16:0 is formed de novo (the other half originates from feed and body adipose tissues;
      • Kalač P.
      • Samková E.
      The effect of feeding various forages on fatty acid composition of bovine milk fat: A review.
      ), only 50% of the C16:0 found in the butterfat was included in the both SMCFA mixture and LCFA mixture. The SMCFA mixture provided 50% of the C16:0 and equivalent proportion (by weight) of C6:0, C8:0, C10:0, C12:0, and C14:0 FA as those found in the butterfat. The LCFA mixture provided 50% of the C16:0 and equivalent proportion (by weight) of C18 FA as found in the butterfat. The SMCFA and LCFA provided by the butterfat were approximately 40 and 60% (by weight) of the total FA, respectively. The butterfat supplemented in 40SM60L treatment was prepared from commercial butter by melting at 37°C and separating the oil layer when it became solid.
      The total duration of the experiment was a single period of 9 wk, including a pretrial period of 1 wk. The FA supplements and butterfat were mixed thoroughly with 800 g Molasses Soyhulls (contains 40% soy molasses and 60% soy hulls; Jinhai Foods Inc., Qinhuangdao, China), and then mixed with 1 kg (wet weight) diet, and consumed by cows of each treatment every morning before feeding during the 8-wk experimental period. The diet was formulated to meet the nutrient requirements (
      China Standard NY/T 34
      Feeding Standard of Dairy Cattle. China Nong Ye Hang Ye Biao Zhun/Tuijian-34.
      ) of cows weighing 600 kg, averaging 150 DIM, and producing 30 kg of milk (3.5% FCM/d). The ingredient and chemical composition of the basal diet are shown in Table 2. Cows were housed in a tie-stall barn and fed individually. Diets were fed as a TMR 3 times daily.
      Table 2Ingredient and chemical composition of the experimental diet (%, DM basis, unless specified otherwise).
      ItemValue
      Ingredient
       Alfalfa hay10.79
       Chinese wildrye10.79
       Corn silage21.77
       Dry distillers grains5.52
       Soybean hull1.2
       Ground corn23.34
       Wheat bran5.29
       Soybean meal7.34
       Cottonseed meal1.68
       Rapeseed meal1.68
       Sunflower seed meal1.2
       Yeast5.29
       Sodium bicarbonate1.08
       Calcium phosphate dibasic0.48
       Limestone0.84
       Sodium chloride0.6
       Calcium carbonate precipitated light0.48
       Magnesium chloride0.12
       Mineral-vitamin premix
      Mineral-vitamin premix contained (per kilogram of DM) a minimum 250,000 IU of vitamin A; 65,000 IU of vitamin D; 2,100 IU of vitamin E; Zn2+ 2,100mg; Cu2+ 540mg; Fe2+ 400mg; Mn2+ 560mg; Se4+ 15mg; I− 35mg; Co2+ 68mg.
      0.48
      Chemical composition
       DM, %50.0
       CP16.07
       NDF39.78
       ADF22.39
       NEL,
      Calculated value (based on China Standard NY/T 34, 2004).
      Mcal/kg of DM
      1.48
       Ca0.9
       P0.42
      1 Mineral-vitamin premix contained (per kilogram of DM) a minimum 250,000 IU of vitamin A; 65,000 IU of vitamin D; 2,100 IU of vitamin E; Zn2+ 2,100 mg; Cu2+ 540 mg; Fe2+ 400 mg; Mn2+ 560 mg; Se4+ 15 mg; I 35 mg; Co2+ 68 mg.
      2 Calculated value (based on
      China Standard NY/T 34
      Feeding Standard of Dairy Cattle. China Nong Ye Hang Ye Biao Zhun/Tuijian-34.
      ).

      Sampling, Measurements, and Analyses

      The feed offered and feed refused were recorded for individual cows daily. Orts were restricted to 5 to 10% of intake on an as-fed basis. The offered TMR were sampled daily and frozen at −20°C. Samples of orts were collected from each cow, composited for each treatment, and frozen at −20°C until analysis. Weekly representative samples of TMR and orts were analyzed for DM content by oven-drying at 60°C for 48 h. Dietary formulations were adjusted weekly during the experiment period to account for small changes in ingredient DM content. Dried feed samples from each week were ground through a Cyclotec 1093 mill (Tecator, Hoganas, Sweden) using a 1-mm screen and analyzed for composition. Samples were further dried at 105°C for 2 h to determine the absolute DM, and chemical analyses were expressed on the basis of the final absolute DM. Content of CP in feed samples was determined using the macro-Kjeldahl nitrogen test with a Kjeltec digester 20 and Kjeltec System 1026 distilling unit (Tecator). Contents of NDF and ADF were determined using the basic procedure of
      • 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.
      . In the procedure for NDF determination, sodium sulfite was not used, but heat-stable amylase (type XI-A from Bacillus subtilis; Sigma-Aldrich Corp., St. Louis, MO) was added to the substrate before the procedure.
      The daily DMI of individual cows was calculated by subtracting the weekly mean orts from the weekly mean feed offered. Cows were milked 3 times daily, and the milk yield of individual cows was recorded consecutively 3 d of each week. On the last day of each week, milk samples from individual cows were collected from 3 consecutive milkings and composited based on the average milk production at each milking (morning, afternoon, and night; volume ratio: 4:3:3). One aliquot of each milk sample was stored with preservative (bronopol tablet; D&F Control System Inc., Dublin, ON, Canada) at 4°C for analysis of fat, protein, lactose, TS, nonfat solids, CN, citric acid, and urea content using mid-infrared analysis (Foss MilkoScan, Foss Food Technology Corp., Eden Prairie, MN). Another aliquot was stored at −20°C until analyzed for FA composition.
      Fatty acid analysis was done according to the method described by
      • Bu D.P.
      • Wang J.Q.
      • Dhiman T.R.
      • Liu S.J.
      Effectiveness of oils rich in linoleic and linolenic acids to enhance conjugated linoleic acid in milk from dairy cows.
      , with minor changes as indicated. The frozen milk samples from individual cows were thawed in a refrigerator at 4°C, and centrifuged at 5,000 × g for 20 min at 8°C to separate fat from milk. The fat cake was transferred to a 5-mL tube, and 20 mg of the fat was esterified using the method containing with NaOCH3:methanol followed by HCl:methanol, described by
      • Kramer J.K.G.
      • Fellner V.
      • Dugan M.E.R.
      • Sauer F.D.
      • Mossoba M.M.
      • Yurawecz M.P.
      Evaluating acid and base catalysts in the methylation of milk and rumen fatty acids with special emphasis on conjugated dienes and total trans fatty acids.
      . Fatty acid methyl esters were separated by using an Agilent 6890 GC (Agilent Technologies, Santa Clara, CA) fit ted with a flame-ionization detector. The samples containing methyl esters in hexane (2 μL) were injected through the split injection port (50:1) onto an HP-88 fused silica 100 m × 0.25 mm column with a 0.20-μm film (Agilent Technologies). The oven temperature was initially 120°C for 10 min and was increased to 230°C at 1.5°C/min and held at that temperature for 30 min. The injector and detector temperatures were maintained at 250°C and 280°C, respectively, and the total run time was 113.33 min. The qualitative external standard method was used in this study. Each peak was identified using known standards of FA and FA methyl esters (Nu-Chek Prep, Elysian, MN; Matreya, Pleasant Gap, PA; Supelco 37 Component FA methyl esters mix, Supelco Inc., Bellefonte, PA). The percentage of each FA was calculated by dividing the area under the FA peak by the sum of the areas for all reported FA peaks. The yield of FA was calculated by multiplying the individual milk FA by milk fat yield and by a coefficient of 93.3% (
      • Glasser F.
      • Doreau M.
      • Ferlay A.
      • Chilliard Y.
      Technical note: Estimation of milk fatty acid yield from milk fat data.
      ). Fatty acids were reported as grams per hundred grams of total FA.

      Statistical Analysis

      The milk yield, milk composition, and milk FA composition were analyzed as a randomized block design with repeated measures using the MIXED procedures of SAS (version 9.0, SAS Institute Inc., Cary, NC). The fixed effects consist of treatment, week, and treatment × week interaction. The variance for cow nested within treatment was used as random error term to test the main effect of treatment. Data from the pretrial period were used as covariates for milk yield and milk composition analysis, and DIM throughout the whole experiment was used as covariate for milk FA composition. The covariance structure was auto-regressive order (1), and downward degrees of freedom using the Kenward-Roger method. Data are presented as covariate-adjusted least squares means with their standard error of the mean. All data were tested for linear and quadratic effects of the 3 supplements. The significance level was declared at P < 0.05 and the trend was declared at P = 0.05 to 0.10.
      The model used for milk composition and milk FA analysis was
      Yijk=μ+Ti+Dj(i)+Wk+(TW)ik×(B+φi)×Xij+Eijk,


      where Yijk = dependent variable measured at week k on the jth cow assigned to the ith treatment; μ = population mean; Ti = treatment effect; Dj(i) = random effect of the jth cow within the ith treatment; Wk = week effect; (TW)ik = fixed interaction effect between treatment and week; b = the common regression coefficient of pre-treatment data (or DIM) of Xij; φi = the slope deviation of the ith treatment from the common slope b; Xij = the pretreatment data (or DIM) of cow j on treatment i; and Eijk = random error associated with the jth cow assigned to the ith treatment at week k.

      Results and discussion

      The average values of DMI, milk yield, and milk composition were presented in Table 3. Days in milk and milk yield were not affected by the supplements, nor were the 3.5% FCM yield, ECM yield, and milk production efficiency (ECM/DMI). It has been demonstrated that abomasal infusion of 400 g/d butterfat or dietary supplementation of 400 g/d SMCFA had no effect on DMI (
      • Kadegowda A.K.G.
      • Plperova L.S.
      • Delmonte P.
      • Erdman R.A.
      Abomasal infusion of butterfat increases milk fat in lactating dairy cows.
      ; emsp
      • Vyas D.
      • Teter B.B.
      • Erdman R.A.
      Milk fat responses to dietary short and medium chain fatty acids in lactating dairy cows.
      ).
      • Hristov A.N.
      • Vander Pol M.
      • Agle M.
      • Zaman S.
      • Schneider C.
      • Ndegwa P.
      • Vaddella V.K.
      • Johnson K.
      • Shingfield K.J.
      • Karnati S.K.R.
      Effect of lauric acid and coconut oil on ruminal fermentation, digestion, ammonia losses from manure, and milk fatty acid composition in lactating cows.
      reported that 530 g/d of coconut oil added directly into the rumen via the cannula did not affect DMI. However,
      • Grummer R.R.
      • Socha M.T.
      Milk fat composition and plasma energy metabolite concentration in lactating cows fed medium-chain triglycerides.
      reported that DMI was decreased by supplementation with medium-chain triacylglycerol.
      • Kongmun P.
      • Wanapat M.
      • Pakdee P.
      • Navanukraw C.
      • Yu Z.
      Manipulation of rumen fermentation and ecology of swamp buffalo by coconut oil and garlic powder supplementation.
      reported that the supplementation of 7% coconut oil in concentrate significantly reduced DMI in buffaloes. The different effects of these lipid supplements on DMI might have been because the amounts added were different in these studies.
      Table 3Dry matter intake, milk yield, and milk composition of cows supplemented with 20SM80L, 40SM60L, and 60SM40L
      20SM80L=supplemented with 400 g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L=supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L=supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      ItemTreatmentSEM
      SEM=standard error of least squares means.
      P-value
      20SM80L40SM60L60SM40LTreatmentWeekTreatment × WeekLinearQuadratic
      DMI, kg/d16.2916.1015.990.120.26<0.010.230.110.80
      Milk yield, kg/d23.5523.9921.850.970.260.020.490.250.27
      3.5% FCM,
      3.5% FCM=0.432 × milk (kg)+16.216 × fat (kg); Dairy Records Management Systems (2011).
      kg/d
      25.9026.8725.461.240.710.230.260.810.44
      ECM,
      ECM=0.327 × milk (kg)+12.95 × fat (kg)+7.65 × protein (kg); Dairy Records Management Systems (2011).
      kg/d
      26.6227.3525.751.240.660.240.250.630.45
      Efficiency, ECM/DMI1.721.591.510.100.370.150.020.170.85
      Fat, %4.014.204.410.110.06<0.010.070.020.96
      Fat yield, kg/d0.970.990.970.050.960.130.180.990.78
      Protein, %3.463.433.480.040.740.810.470.730.48
      Protein yield, kg/d0.830.820.760.040.45<0.010.340.230.69
      Lactose, %4.624.624.660.040.680.380.500.470.63
      TS, %13.09b13.26
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      b
      13.55
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.120.04<0.010.190.010.68
      SNF, %9.008.959.070.050.300.210.670.340.20
      a ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      1 20SM80L = supplemented with 400 g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L = supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L = supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      2 SEM = standard error of least squares means.
      3 3.5% FCM = 0.432 × milk (kg) + 16.216 × fat (kg);

      Dairy Records Management Systems. 2011. DHI Glossary. Accessed February 2011. http://www.drms.org/PDF/materials/glossary.pdf.

      .
      4 ECM = 0.327 × milk (kg) + 12.95 × fat (kg) + 7.65 × protein (kg);

      Dairy Records Management Systems. 2011. DHI Glossary. Accessed February 2011. http://www.drms.org/PDF/materials/glossary.pdf.

      .
      As the ratios of SMCFA to LCFA in the supplements increased, milk fat percentage tended to increase (P < 0.10) linearly (P < 0.05), and the TS percentage increased (P < 0.05) linearly (P < 0.05), whereas milk fat yield, nonfat solids percentage, protein percentage and yield, as well as the lactose percentage were not dif ferent in those treatments. Similarly,
      • Vyas D.
      • Teter B.B.
      • Erdman R.A.
      Milk fat responses to dietary short and medium chain fatty acids in lactating dairy cows.
      reported that milk fat concentration was increased by the increasing amounts of SMCFA supplemented in the diet of lactating cows. In previous research, supplementing myristic acid and palmitic acid to the diet of lactating cows increased the milk fat percentage (
      • Steele W.
      • Moore J.H.
      The effect of a series of saturated fatty acids in the diet on milk-fat secretion in the cow.
      ), and intravenous infusion of trilaurin and trimyristin also had positive effect on the milk fat yield (
      • Storry J.E.
      • Tuckley B.
      • Hall A.J.
      The effects of intravenous infusions of triglycerides on the secretion of milk fat in the cow.
      ).
      Conversely, the milk fat percentage tended to decrease (P < 0.10) linearly (P < 0.05) with the increasing ratios of LCFA to SMCFA. Although supplements of saturated LCFA tended to increase the milk fat yield (
      • Steele W.
      • Moore J.H.
      The effect of a series of saturated fatty acids in the diet on milk-fat secretion in the cow.
      ; emsp
      • Drackley J.K.
      • Klusmeyer T.H.
      • Trusk A.M.
      • Clark J.H.
      Infusion of long-chain fatty acids varying in saturation and chain length into the abomasums of lactating dairy cows.
      ), it has been demonstrated that exogenous C18 FA (stearic, oleic, and linoleic acids) inhibited de novo FA synthesis and the incorporation of FA synthesized de novo into triacylglycerols (
      • Hansen H.O.
      • Knudsen J.
      Effect of exogenous long-chain fatty acids on lipid biosynthesis in dispersed ruminant mammary gland epithelial cells: Esterification of long-chain exogenous fatty acid.
      ,
      • Hansen H.O.
      • Knudsen J.
      Effect of exogenous long-chain fatty acids on individual fatty acid synthesis by dispersed ruminant mammary gland cells.
      ).
      • Kadegowda A.K.G.
      • Plperova L.S.
      • Delmonte P.
      • Erdman R.A.
      Abomasal infusion of butterfat increases milk fat in lactating dairy cows.
      reported that abomasal infusion of butterfat, which contains both SMCFA and LCFA, increased milk fat concentration, whereas infusion of only the LCFA present in butterfat had no effect. Short- and medium-chain fatty acids might contribute more to milk fat synthesis than LCFA; SMCFA are transported by the portal venous system and reach the liver more rapidly than do LCFA, whereas LCFA move via the ex trahepatic tissues and may be partially retained (
      • Bach A.C.
      • Babayan V.K.
      Medium-chain triglycerides: An update.
      ).
      • Hansen H.O.
      • Knudsen J.
      Effect of exogenous long-chain fatty acids on lipid biosynthesis in dispersed ruminant mammary gland epithelial cells: Esterification of long-chain exogenous fatty acid.
      reported that palmitic and lauric acids stimulated the secretion of FA from mammary gland cells and the incorporation of those FA into milk as triacylglycerol.
      • Kadegowda A.K.G.
      • Plperova L.S.
      • Delmonte P.
      • Erdman R.A.
      Abomasal infusion of butterfat increases milk fat in lactating dairy cows.
      concluded that palmitic acid, the preferred substrate for the initial acylation of sn-1 position, may stimulate triacylglycerol synthesis in the mammary gland, but because the amounts of palmitic acid in the supplements were similar, the effect of palmitic acid on milk fat synthesis was not clear in this study.
      The milk FA composition (g/100 g of total FA) and milk FA yield (g/d) of individual FA are presented in Table 4 and Table 5, respectively. As the ratios of SMCFA to LCFA in the supplements increased, concentration of total SMCFA, which derived from de novo synthesis, tended to increase (P < 0.10) linearly (P < 0.10). Concentrations and yields of C13:0, C15:0, C16:1, C20:2, C22:0, cis-8,11,14 C20:3, and cis-11,14,17 20:3, as well as the concentration of C4:0, increased (P < 0.05) quadratically (P < 0.05), and were highest in milk from cows that received butterfat supplement (40SM60L), except cis-8,11,14 C20:3 and cis-11,14, 17 20:3, which were lower (P < 0.05) than in 20SM80L and 60SM40L. The concentrations of C12:0 and C14:1, as well as yield of trans-9 C18:1, tended to increase (P < 0.10) linearly (P < 0.15), and the concentration of C14:0 increased (P < 0.05) linearly (P < 0.05) with increasing amounts of those FA supplemented. Similar changes were observed that supplementing pure FA (C12:0, C14:0, C16:0, C18:0, or C18:1) increased those individual FA in milk fat (
      • Steele W.
      • Moore J.H.
      The effect of a series of saturated fatty acids in the diet on milk-fat secretion in the cow.
      ,
      • Steele W.
      • Moore J.H.
      The effects of mono-unsaturated and saturated fatty acids in the diet on milk-fat secretion in the cow.
      ). Concentrations of C6:0, C8:0, and C10:0 were not influenced by the supplements and thus were most likely metabolized by other tissues. Kadegowda (2008) reported that the most efficient transfers of FA, from the lipids infused into milk fat, were C14:0 and C12:0 with transfer efficiency of 83 and 67%, respectively. As the amounts of palmitic acids in the supplements were similar, C16:0 was not different among the treatments.
      Table 4Milk fatty acids composition of cows supplemented with 20SM80L, 40SM60L, and 60SM40L
      20SM80L=supplemented with 400 g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L=supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L=supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      FA
      Expressed as numbers of carbons:numbers of double bonds.
      Treatment, g/100 g of total FASEM
      SEM=standard error of least squares means.
      P-value
      20SM80L40SM60L60SM40LTreatmentWeekTreatment × WeekLinearQuadratic
      4:03.57
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      b
      3.86
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      3.20b0.190.04<0.01<0.010.200.04
      6:02.022.251.970.100.10<0.01<0.010.770.04
      8:01.121.251.150.060.20<0.01<0.010.730.08
      10:02.352.562.530.130.48<0.01<0.010.350.42
      11:00.030.050.040.010.230.020.800.230.20
      12:02.702.953.150.130.08<0.010.020.030.86
      13:00.03b0.09
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.04b0.01<0.01<0.01<0.010.11<0.01
      14:09.98b10.83
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      11.43
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.23<0.01<0.01<0.01<0.010.63
      14:11.121.191.340.060.07<0.010.150.030.65
      15:00.89b1.10
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.93b0.03<0.010.070.510.38<0.01
      16:031.0831.2030.830.460.84<0.01<0.010.710.66
      16:10.43b0.62
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.42b0.01<0.01<0.01<0.010.58<0.01
      17:00.440.420.430.030.830.410.140.840.56
      18:010.9810.5110.340.380.51<0.010.580.260.73
      trans-9 18:11.030.990.790.090.150.530.470.110.44
      trans-11 18:11.261.401.300.070.37<0.010.040.720.17
      cis-9 18:122.84
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      20.62b21.90
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      b
      0.700.09<0.010.330.370.04
      trans-9,trans-12 18:2Trace0.19Trace0.170.590.790.831.000.32
      cis-9,cis-12 18:22.943.113.080.100.49<0.010.950.360.40
      cis-9,trans-11 CLA
      Conjugated linoleic acids.
      0.570.600.590.030.79<0.01<0.010.760.53
      trans-10,cis-12 CLATrace0.01Trace0.010.080.370.241.000.03
      18:30.470.480.460.020.67<0.010.870.850.40
      20:00.050.080.040.040.640.790.820.780.41
      20:10.070.070.060.010.140.230.240.450.10
      20:2Traceb0.31
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.03b0.03<0.01<0.01<0.010.61<0.01
      cis-8,11,14 20:30.01
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      Traceb0.01
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      <0.01<0.010.160.740.94<0.01
      cis-11,14, 17 20:33.86
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      3.03b3.85
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.16<0.01<0.01<0.010.96<0.01
      22:00.06b0.14
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.07b0.01<0.010.510.160.66<0.01
      Others0.050.100.080.060.880.500.990.740.65
      Summations
       <16:023.87b26.14
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      25.77
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      b
      0.670.06<0.010.010.070.11
       >16:044.6942.0542.990.880.12<0.01<0.010.200.19
       ≥20:04.123.734.120.180.19<0.01<0.010.990.07
       SFA65.3467.3566.160.750.17<0.01<0.010.460.08
       MUFA26.8024.8925.820.710.18<0.010.040.360.10
       PUFA7.897.758.030.300.79<0.01<0.010.750.56
      a ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      1 20SM80L = supplemented with 400 g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L = supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L = supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      2 Expressed as numbers of carbons:numbers of double bonds.
      3 SEM = standard error of least squares means.
      4 Conjugated linoleic acids.
      Table 5Milk fatty acids yield of cows from 20SM80L, 40SM60L, and 60SM40L
      20SM80L=supplemented with 400 g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L=supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L=supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      FA
      Expressed as numbers of carbons:numbers of double bonds.
      Treatment, g/100 g of total FASEM
      SEM=standard error of least squares means.
      P-value
      20SM80L40SM60L60SM40LTreatmentWeekTreatment × WeekLinearQuadratic
      4:031.8735.6728.523.030.230.01<0.010.460.13
      6:017.9920.7517.591.710.340.090.020.880.15
      8:09.9411.5310.230.930.420.190.040.840.20
      10:020.8623.4122.551.900.640.620.120.550.45
      11:00.280.410.380.060.300.260.720.260.26
      12:024.0826.7928.131.960.380.740.330.170.77
      13:00.24b0.81
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.37b0.06<0.01<0.01<0.010.14<0.01
      14:088.9398.41101.586.300.380.370.400.180.67
      14:110.1110.7311.800.790.35<0.010.570.160.81
      15:07.88b9.96
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      8.24b0.520.020.480.280.64<0.01
      16:0278.14282.74274.0117.170.930.140.170.870.74
      16:13.78b5.59
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      3.69b0.24<0.01<0.01<0.010.80<0.01
      17:03.883.823.820.380.990.480.550.910.95
      18:097.7996.0391.455.710.73<0.010.540.460.83
      trans-9 18:19.208.807.070.700.090.290.500.060.41
      trans-11 18:111.1312.4811.470.650.30<0.010.030.730.13
      cis-9 18:1203.69185.65193.079.450.42<0.010.580.460.26
      trans-9,trans-12 18:2Trace1.27Trace1.160.610.820.871.000.34
      cis-9,cis-12 18:226.1427.9927.241.380.65<0.010.820.600.42
      cis-9,trans-11 CLA
      Conjugated linoleic acids.
      5.115.375.180.250.74<0.01<0.010.860.45
      trans-10,cis-12 CLATrace
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      b
      0.12
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      Traceb0.040.040.260.121.000.01
      18:34.154.354.100.220.66<0.010.780.880.38
      20:00.470.640.310.290.650.800.850.730.45
      20:10.600.660.510.050.080.040.090.300.07
      20:2Traceb2.78
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.29b0.35<0.01<0.01<0.010.60<0.01
      cis-8,11,14 20:30.10
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.02b0.09
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.01<0.010.070.760.95<0.01
      cis-11,14,17 20:333.93
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      27.22b33.68
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      1.850.02<0.01<0.010.93<0.01
      22:00.53b1.21
      ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      0.590.08<0.010.100.020.64<0.01
      Others0.450.770.830.570.910.560.980.670.85
      Summations
       <16:0212.01238.47229.2715.910.500.300.150.470.35
       >16:0397.28378.88379.5917.290.72<0.010.400.500.64
       ≥20:036.2033.2436.212.130.50<0.01<0.011.000.24
       SFA582.52612.71588.0136.180.810.210.260.920.52
       MUFA238.68223.83227.7610.660.62<0.010.640.500.46
       PUFA69.8669.1070.763.570.94<0.01<0.010.870.77
      a ,bMeans in the same row with different superscripts differ significantly for treatment effect.
      1 20SM80L = supplemented with 400 g/d of FA supplement, containing 20% short- and medium-chain fatty acid (SMCFA) mixture and 80% of long-chain fatty acid (LCFA) mixture; 40SM60L = supplemented with 400 g/d of butterfat, providing 40% SMCFA and 60% LCFA (approximately); 60SM40L = supplemented with 400 g/d of FA supplement, containing 60% SMCFA mixture and 40% LCFA mixture.
      2 Expressed as numbers of carbons:numbers of double bonds.
      3 SEM = standard error of least squares means.
      4 Conjugated linoleic acids.

      Conclusions

      Fat content and total SMCFA concentration in milk fat tended to increase linearly with increasing ratios of SMCFA to LCFA in the unprotected lipid supplementation. Increasing ratios of SMCFA to LCFA can potentially improve milk fat synthesis. However, as both SMCFA and LCFA have positive effects on milk fat synthesis, further studies are needed to test the role of SMCFA and LCFA by abomasal infusion of the FA supplements and to refine the most effective ratio of SMCFA to LCFA to promote milk fat synthesis.

      Acknowledgements

      We gratefully acknowledge Donald Palmquist, professor emeritus at The Ohio State University (Columbus), for his assistance with editing this paper. The study was supported by National Basic Research Program (973) of China (grant no.2011CB100805) and grants (2012BAD12B02-5; 2004DA125184G1103) by Ministry of Science and Technology.