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Inclusion of sainfoin (Onobrychis viciifolia) silage in dairy cow rations affects nutrient digestibility, nitrogen utilization, energy balance, and methane emissions
Sainfoin (Onobrychis viciifolia) is a tanniniferous legume forage that has potential nutritional and health benefits preventing bloating, reducing nematode larval establishment, improving N utilization, and reducing greenhouse gas emissions. However, the use of sainfoin as a fodder crop in dairy cow rations in northwestern Europe is still relatively unknown. The objective of this study was to evaluate the effect of sainfoin silage on nutrient digestibility, animal performance, energy and N utilization, and CH4 production. Six rumen-cannulated, lactating dairy cows with a metabolic body weight (BW0.75) of 132.5 ± 3.6 kg were randomly assigned to either a control (CON) or a sainfoin (SAIN)-based diet over 2 experimental periods of 25 d each in a crossover design. The CON diet was a mixture of grass silage, corn silage, concentrate, and linseed. In the SAIN diet, 50% of grass silage dry matter (DM) of the CON diet was exchanged for sainfoin silage. The cows were adapted to 95% of ad libitum feed intake for a 21-d period before being housed in climate-controlled respiration chambers for 4 d, during which time feed intake, apparent total-tract digestibility, N and energy balance, and CH4 production was determined. Data were analyzed using a mixed model procedure. Total daily DM, organic matter, and neutral detergent fiber intake did not differ between the 2 diets. The apparent digestibility of DM, organic matter, neutral detergent fiber, and acid detergent fiber were, respectively, 5.7, 4.0, 15.7, and 14.8% lower for the SAIN diet. Methane production per kilogram of DM intake was lowest for the SAIN diet, CH4 production as a percentage of gross energy intake tended to be lower, and milk yield was greater for the SAIN diet. Nitrogen intake, N retention, and energy retained in body protein were greater for the SAIN than for the CON diet. Nitrogen retention as a percentage of N intake tended to be greater for the SAIN diet. These results suggest that inclusion of sainfoin silage in dairy cow rations reduces CH4 per kilogram of DM intake and nutrient digestibility. Moreover, sainfoin silage improves milk production and seems to redirect metabolism toward body protein accretion at the expense of body fat.
Methane (CH4) is the second most important gas involved in global warming, with CH4 from livestock accounting for 6.3% of the human-induced production of greenhouse gases when expressed in CO2-equivalents (
Tackling climate change through livestock: A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO),
Rome, Italy2013
). Among livestock, ruminants are the main contributors, accounting for 65% of emissions. Ruminants typically lose between 2 and 12% of their ingested energy as eructated CH4 (
). These energy losses are not only an environmental concern but also reduce efficiencies in ruminant production. Reducing the enteric CH4 emissions of cattle would lessen the impact of livestock production on the environment and potentially decrease the costs of production by increasing feed efficiency. A decrease in CH4 emissions from ruminants can be achieved by improving feed quality (
Sainfoin (Onobrychis viciifolia) is a tanniniferous legume that is grown under different climatic conditions in Europe, Asia, and western North America, primarily in calcareous soils (
), and it is useful for grazing, hay-making, and for silage. Sainfoin is reported to support a similar animal performance compared with grass and grass-clover hay when offered as hay to dairy cows (
). In addition, due to the CT in sainfoin (compared with alfalfa), N excretion is partially redirected from urine to feces in sheep and, therefore, could reduce ammonia (NH3) volatilization from ruminant manure (
Benefit of including bioactive legumes (sainfoin, red clover) in grass-based silages on ruminant production and pollutant emissions. Université Blaise Pascal, Vet Agro Sup, UMR Herbivores,
Clermont-Ferrand, France2015
Impact of variation in structure of condensed tannins from sainfoin (Onobrychis viciifolia) on in vitro ruminal methane production and fermentation characteristics.
J. Anim. Physiol. Nutr.2015; (b, http://dx.doi.org/10.1111/jpn.12336)
). Limited data, however, are available on the effect of sainfoin on CH4 emission in vivo, and to the authors’ knowledge, no data are available on the use of sainfoin silage in TMR typically fed to dairy cows. The hypothesis of this study was that inclusion of sainfoin silage at the expense of grass silage in a TMR for dairy cows would reduce CH4 emission, alter N metabolism, and affect milk production. Therefore, the objective of this study was to compare enteric CH4 emissions, diet digestibility, energy and protein utilization, and N excretions from dairy cows receiving TMR based on either sainfoin silage (a CT-containing forage) or grass silage (a CT-free forage).
Materials and Methods
Experimental Design
The experiment was approved by the Institutional Animal Care and Use Committee of Wageningen University (Wageningen, the Netherlands) and executed in accordance with European Union directive 2010/63/EU implemented by the Dutch legislation on the use of experimental animals. The experiment was conducted from February to April 2014 at the Carus Research Facilities of Wageningen University. The experiment followed a crossover design with 2 dietary treatments and 6 rumen-cannulated (Type 1C; Bar Diamond Inc., Parma, ID) lactating multiparous dairy cows with a mean ± SD metabolic BW (BW0.75) of 132.5 ± 3.6 kg, 214 ± 72 DIM, and an average milk production of 23.1 ± 2.8 kg/d at the start of the experiment. Cows were paired based on parity and milk production; within pairs, cows were randomly assigned to receive either a grass and corn silage-based control (CON) diet or a sainfoin-grass and corn silage-based (SAIN) diet (Table 1) for an experimental period of 25 d (adaptation period from d 8–29 and subsequent measurement period from d 29–33), after which animals were changed to the other dietary treatment for a second 25-d period. Before both experimental periods, all animals received the CON diet for a 7-d period (d 1–7).
Table 1Feedstuff and chemical compositions (g/kg of DM unless otherwise noted) of TMR containing grass silage (CON) or sainfoin silage (SAIN) used in the experiment
Grass silage: DM=366g/kg product; chemical composition (g/kg of DM): OM=907.1, CP=145.9, NDF=508.6, ADF=306.3, ADL=14.3, gross energy (GE)=19.2 MJ/kg of DM, NEL=7.4 MJ/kg of DM; pH=5.4.
Sainfoin silage was a mixture of cultivar ‘Zeus’ silage from clay soil and cultivar ‘Esparcette’ from sandy soil (ratio between silages from ‘Zeus’ and ‘Esparcette’=70:30 on DM basis). Sainfoin ‘Zeus’ silage: DM=200g/kg product; chemical composition (g/kg of DM): OM=785.2, CP=212.3, NDF=346.0, ADF=305.3, ADL=67.0, GE=17.1 MJ/kg of DM, NEL=4.3 MJ/kg of DM; condensed tannins (CT)=24.0, pH=5.5. Sainfoin ‘Esparcette’ silage: DM=380g/kg of product; chemical composition (g/kg of DM): OM=923.5, CP=96.5, NDF=441.0, ADF=336.5, ADL=59.6, GE=18.2 MJ/kg of DM, NEL=5.3 MJ/kg of DM; CT=31.0, pH=5.2.
Linseed: DM=922g/kg of product; chemical composition (g/kg of DM): OM=962.0, CP=239.5, NDF=201.3, ADF=156.2, ADL=29.1, crude fat=417.9, starch=14.3, GE=27.8 MJ/kg of DM, NEL=11.7 MJ/kg of DM.
60.0
60.0
Chemical composition
DM, g/kg of product
444.9
357.2
OM
918.9
891.3
CP
162.7
171.9
NDF
395.7
359.1
ADF
236.7
244.5
ADL
18.6
35.0
Crude fat
37.8
35.1
Starch
97.9
90.9
Gross energy, MJ/kg of DM
19.5
19.0
Condensed tannins
0.0
8.8
1 Values are means for 2 successive measurement periods. For all components, NEL was determined according to
Sainfoin cultivars ‘Zeus’ and ‘Esparcette’ were grown on a clay-type and sandy soil, respectively at the experimental facilities of the Plant Sciences Group (Unifarm) at Wageningen University. Both sainfoin cultivars were harvested at the end of the flowering period in the second vegetation cycle and separately ensiled in round bales. The characteristics of the silages are included in Table 1. The SAIN diet contained a mixture of both sainfoin silages in a ratio of 70:30 on DM basis for ‘Zeus’ and ‘Esparcette’, respectively (see Table 1). The CON diet was composed of grass silage (600 g/kg of DM), corn silage (100 g/kg of DM), concentrate (240 g/kg of DM), and linseed (60 g/kg of DM) prepared as a TMR. In the SAIN diet, half of the grass silage DM was replaced by the sainfoin silage mixture. The TMR were prepared twice a week, and daily portions per animal were weighed into bins and stored overnight at 4°C until feeding to limit nutrient losses through respiration (
). During each feed preparation, samples were taken from individual feedstuffs, which were pooled per week and stored at −20°C pending chemical analyses. Diet formulation was identical for both experimental periods and the resulting chemical composition are summarized in Table 1. Diets were formulated to meet the energy and protein requirements of dairy cows (
Cows were fed individually and feed residues were collected to determine DMI throughout the experiment. The cows received their feed twice daily in equal portions at 0600 and 1600 h. The cows were fed ad libitum during the 7-d periods preceding the 25-d experimental periods. From d 8 to 33 of each experimental period, diets were offered at 95% of ad libitum intake to minimize feed residues. When present, feed residues were collected once per day before the morning feeding and twice per day from d 29 to 33 of each period.
During the first 21 d (d 8–29) of each 25-d experimental period, cows were housed in tiestalls before being transported (100 m, 10 min) in a trailer and housed individually in climate-controlled respiration chambers (CRC) for 4 d (d 29–33) to measure CH4 production, O2 consumption, and CO2 production, feed intake, feces and urine production to determine apparent total-tract digestibility, energy and N balance, and respiratory quotient (RQ). On d 8, 18, and 25 at 1500 h, cows were housed for 48 h in the CRC for measurement of CH4 and rumen fluid sampling. The data of the latter measurements are provided elsewhere. The CRC were described in detail by
. Briefly, the volume of the individual chambers was 35 m3, and relative humidity was maintained at 70% at a temperature of 16°C. Cows in the CRC were exposed to 16 h of light per day with the ventilation rate set at 42 m3/h per compartment, and the inlet and exhaust air of each compartment sampled at 10-min intervals. Gas concentrations and ventilation rates were corrected for pressure, temperature, and humidity to obtain standard temperature-pressure dew point volumes of inlet and exhaust air. Staff entered each CRC compartment twice daily at 0600 and 1600 h for approximately 30 min for milking and feeding. The gas measurements during these periods were excluded from data analysis. Water was freely available during the entire experiment.
Measurements and Sampling
Feed Intake and BW
Feed intake measurements determined from d 29 to 33 in each experimental period were used to calculate average nutrient intake per cow per day. Grass silage, corn silage, sainfoin silage, concentrate, and linseed were sampled and stored at −20°C before being freeze-dried and ground in an cross beater mill (Peppink 100 AN, Deventer, the Netherlands) to pass through a 1-mm sieve. After grinding, all samples were stored at 4°C pending analysis. Feed ingredient samples were analyzed for DM, ash, N, NDF, ADF, ADL, crude fat, starch, gross energy (GE), and CT.
In the CRC, feed residues were collected and weighed twice daily, before the morning and afternoon feedings, and stored at 4°C. Residues were pooled per cow per period and then subsampled. Feed residue subsamples were oven-dried at 60°C and ground in a cross beater mill (Peppink 100 AN) to pass through a 1-mm sieve before DM analysis. Feed DMI was calculated by subtracting the dry weight of feed residues from the dry weight of feed offered. Body weight of cows was weighed and recorded immediately after entering and just before leaving the CRC.
Total Collection for Digestibility and Metabolizability
Apparent total-tract digestibility and metabolizability of nutrients were determined by quantitative separate collection of urine and feces (Figure 1). Cows were fitted with a handmade external urinary collection device constructed from a cone-shaped rubber funnel (0.5 mm; RX Superba, Eriks, Ede, the Netherlands), attached with Velcro to a rubber template (1.5 mm; RX Superba, Eriks) that fitted over the vulva and was glued to the shaved skin with medical glue (Hollister BV, Amersfoort, the Netherlands). The funnel was attached to a spiral polyvinyl chloride flexible tube (Delphinus S 32.0 × 37.6 mm, Mees van den Brink, Veenendaal, the Netherlands) attached to a sealed collection barrel. Urine was collected twice daily at 0600 and at 1600 h and weighed, and a 0.5% (wt/wt) urine subsample was collected each time and immediately stored at −20°C to prevent NH3 losses. Urine subsamples were analyzed for total N and GE. Nitrogen retention (g/kg of BW0.75 per day) was estimated from N consumed through feed (corrected for orts) and excreted in the feces, urine, and milk. Water that condensed from the chamber air on the heat exchanger was collected and analyzed for N. The ventilated chamber air was sampled continuously and flushed through a 25% solution of hydrosulfuric acid to trap ammonia. The amount of N trapped in acid was determined at the end of the experimental period and used to quantify N released via ventilated chamber air. Both N in condensed water and N trapped in acid were used to determine N retention. Feces were quantitatively collected from the CRC at the end of the 4-d measurement period and homogenized, and 3 subsamples of approximately 500 g each were collected in sealable containers and immediately stored in a freezer at −20°C. Two of the fecal subsamples were then freeze-dried, ground at 1 mm, and stored at 4°C before analysis of DM, ash, N, NDF, ADF, crude fat, starch, and GE. The third fecal subsample was thawed overnight to ambient temperature and analyzed for DM and N in the wet material to determine N retention. Apparent digestibility of nutrients was calculated by the difference between intake and fecal output of the nutrient.
Figure 1Cow in climate-controlled respiration chamber and (insets) urine collection device for quantitative urine collection. Color version available online.
Milk was collected twice daily at 0600 and 1600 h from the cows in the CRC and recorded for individual cows. A milk sample (10 mL) of each milking was collected in a tube containing sodium azide (5 µL) for preservation and analyzed for fat, protein, and lactose contents. Additional representative milk samples (5 g/kg of milk) were taken at each milking, pooled per cow, and stored at −20°C pending analyses for N, urea, and energy in milk. Milk composition reported was corrected for differences in milk yield between individual milking events.
Analytical Procedures
Gross energy was determined using bomb calorimetry (IKA-C700, Janke & Kunkel, Heitersheim, Germany; ISO 9831;
Animal feeding stuffs, animal products, and faeces or urine–Determination of gross calorific value–Bomb calorimeter method. ISO 9831:1998. International Organization for Standardization (ISO),
Geneva, Switzerland1998
Animal feeding stuffs–Determination of moisture and other volatile matter content. ISO 6496:1999. International Organization for Standardization (ISO),
Geneva, Switzerland1999
Animal feeding stuffs–Determination of nitrogen content and calculation of crude protein content–Part 1. Kjeldahl method. ISO 5983–1:2005. International Organization for Standardization (ISO),
Geneva, Switzerland2005
Animal feeding stuffs–Enzymatic determination of total starch content. ISO 15914:2004. International Organization for Standardization (ISO),
Geneva, Switzerland2004
Whole milk–Determination of milk fat, protein and lactose content–Guidance on the operation of mid-infrared instruments. ISO 9622:1999. International Organization for Standardization (ISO),
Geneva, Switzerland1999
Milk–Determination of urea content–Enzymatic method using difference in pH. ISO 14637:2004. International Organization for Standardization (ISO),
Geneva, Switzerland2004
, with slight modifications. In brief, approximately 10 mg of dried plant material was weighed into a screw-cap test tube before 10 mL of acetone-butanol-HCl reagent was added. The latter reagent was prepared daily by first dissolving 150 mg of ammonium ferric sulfate dodecahydrate in 3.3 mL of water and 5 mL of 12 M HCl before adding 42 mL of butanol-1-ol and 50 mL of acetone. The tubes were left at room temperature for 1 h, after which they were heated at 70°C for 2.5 h in the dark, and air-cooled for 45 min to room temperature. The supernatants were transferred to quartz spectrophotometer cuvettes, the spectra were measured using a spectrophotometer (V530 Spectrophotometer, Jasco, Dunmow, UK) from 450 to 650 nm, and the absorption of the anthocyanin peak was recorded. The CT concentration in the plant material was calculated using a standard with known tannin content to give an average response factor of 1 absorbance unit per 25 µg of purified CT. The tannins for this standard were extracted from sainfoin with 70% acetone:water, subjected to Sephadex LH-20 column (GE Healthcare Life Science, Piscataway, NJ) chromatography to obtain fraction 2, which contained 100 g of CT/100 g of fraction (
). The CT concentration in plant material was expressed as a percentage of the total dry weight. Acetone-butanol-HCl reagent was used as a blank and as a diluent to keep maximal absorbance readings of anthocyanin peaks below 1.5 units.
Energy and Nitrogen Balance Calculation
Digestible (DEI) and metabolizable energy intake (MEI) per cow was calculated by subtracting the daily energy excreted in the feces (DEI) and urine and CH4 (MEI) from daily GE intake (GEI) through feed. Heat production (HP) was determined by indirect calorimetry at 10-min intervals (excluding the two 30-min feeding periods) by measuring the exchange of O2, CO2, and CH4 according to the principles described by
). Energy retention (ER) in body mass was calculated by subtracting the daily HP and energy in milk from MEI. Energy retention as body protein (ERp) was derived from the protein gain (N retention × 6.25) multiplied by 23.6 kJ/g (energetic value of body protein;
). Energy retention as fat (ERf) was calculated from the difference between ER and ERp. Energy retention data were expressed per kilogram of BW0.75 per day, where the mean BW per cow per balance period was used to calculate the metabolic BW.
Statistical Analysis
Effects of diet treatments on feed intake, nutrients digestibility, CH4 emissions, and N and energy utilization were tested by ANOVA using the MIXED procedure of SAS (
where Y = the dependent variable, µ = the overall mean, Ai = the effect of animal (i = 1 to 6), Tj = the effect of diet treatments (j = 1 to 2), Pk = the effect of period (k = 1 to 2), and εijk = the residual error term. Treatment and period were independent variables and animal was a random variable. Data are presented as the least squares means and standard error of the means (LSM ± SEM). Differences among main effects were analyzed using Tukey-Kramer’s multiple comparison procedure in the LSMEANS statement of SAS (
) with effects considered significant at P ≤ 0.05 and a trend at 0.05 < P ≤ 0.10. Order was initially included in the model but found to be not significant.
Respiratory quotient, CH4, and HP exchange rates for 60-min periods (expressed per kg of BW0.75 per day) were analyzed by repeated-measures ANOVA, using the MIXED procedure in SAS (2010) and applying a first-order antedependence covariance model (
). Animal, diet, period, day, and hour were included as model main effects. Day was included in the REPEATED statement, with hour nested within day. Animal was included in the SUBJECT statement, with animal nested within diet × period, thus correlating the diurnal measurements on the same animal and diet. Differences among main effects were analyzed using Tukey-Kramer’s multiple comparison procedure in the LSMEANS statement in SAS, with effects considered significant at P ≤ 0.05 and a trend at 0.05 < P ≤ 0.10.
Results
Feed Intake and Animal Performance
Results on feed intake and nutrient digestibility are shown in Table 2. No differences between treatment on DM, OM, NDF, crude fat, or starch intake of the cows were observed. However, N intake was greater (P = 0.027) for the SAIN diet with a trend observed for NDF (P = 0.091) and ADF (P = 0.051). Apparent digestibility of DM, OM, NDF, and ADF were lower (P ≤ 0.009) for the SAIN diet. The absolute amounts of DM and OM digested per day did not differ between treatments, but the amount of N digested tended (P = 0.097) to be greater for the SAIN diet compared with the CON diet. Total milk yield and milk per kilogram of OM digested was greater (P ≤ 0.042) for the SAIN diet (Table 3). Fat- and protein-corrected milk production (FPCM) and total daily milk protein yield tended to be greater (P ≤ 0.082) for the SAIN diet. We detected no differences (P = 0.209) between treatments on milk fat content, whereas milk protein content tended (P = 0.065) to be greater and MUN tended (P = 0.070) to be lower for the CON diet.
Table 2Feed intake and digestibility of macronutrients of a TMR containing grass silage (CON) or sainfoin silage (SAIN) when fed to lactating dairy cows
Methane production expressed in grams per day was not different between the 2 diets (Table 4). However, because of a numerically greater DMI for the SAIN diet, CH4 expressed per kilogram of DMI was lower (P = 0.005) for the SAIN diet. Methane expressed relative to GEI tended (P = 0.063) to be lower for the SAIN diet. However, CH4 expressed per kilogram of milk and per kilogram of FPCM were not different between the 2 diets.
Table 4Methane (CH4) emissions from dairy cows fed a TMR containing grass silage (CON) and sainfoin silage (SAIN)
We found no differences between treatments on GEI, CH4, energy in milk, energy in urine, or HP (Table 5). Energy in feces was greater (P = 0.039) for the SAIN diet compared with the CON diet. As a result, total energy retention of the cows was highest (P = 0.025) for the CON diet. Total energy retention expressed relative to GEI (ER% of GEI) was lower (P = 0.050) for the SAIN diet; ERp was greater (P = 0.038), whereas ERf was lower (P = 0.007) for cows fed the SAIN diet.
Table 5Energy balance (kJ/kg of BW0.75 per day, unless stated otherwise) and N balance (g/kg of BW0.75 per day, unless stated otherwise) in dairy cows fed a TMR containing grass silage (CON) or sainfoin silage (SAIN)
GEI=gross energy intake; DEI=digestible energy intake (GEI – energy in feces); MEI=ME intake (GEI – energy in feces – energy in urine – CH4); ER=energy retention (ER total=MEI – heat production – energy in milk); ERp=energy retention as body protein [N retention (g) × 6.25×23.6 kJ/g]; ERf=energy retention as body fat (ER – ERp); energy efficiency=[(energy in milk/GEI) × 100]; RQ=respiration quotient (CO2 produced/O2 consumed).
N retention=N intake – N feces – N urine – N milk – N in condensate collected from heat exchanger – N trapped from the outflowing air; N efficiency=(N in milk/N intake) × 100.
N intake
3.53
3.97
0.249
0.022
0.359
N feces
1.19
1.37
0.068
0.038
0.650
N urine
1.29
1.33
0.101
0.584
0.084
N milk
0.92
0.97
0.112
0.414
0.416
N retention
0.11
0.27
0.047
0.037
0.323
N retention (% N intake)
3.21
6.88
1.309
0.083
0.204
N efficiency (%)
25.86
24.22
1.514
0.295
0.128
1 Differences between treatment and period were considered significant at P ≤ 0.05.
2 Mean BW per cow per balance period was used to calculate metabolic BW (BW0.75).
3 GEI = gross energy intake; DEI = digestible energy intake (GEI – energy in feces); MEI = ME intake (GEI – energy in feces – energy in urine – CH4); ER = energy retention (ER total = MEI – heat production – energy in milk); ERp = energy retention as body protein [N retention (g) × 6.25 × 23.6 kJ/g]; ERf = energy retention as body fat (ER – ERp); energy efficiency = [(energy in milk/GEI) × 100]; RQ = respiration quotient (CO2 produced/O2 consumed).
4 N retention = N intake – N feces – N urine – N milk – N in condensate collected from heat exchanger – N trapped from the outflowing air; N efficiency = (N in milk/N intake) × 100.
Cows had greater (P = 0.022) N intake when fed the SAIN diet than fed the CON diet (Table 5). We detected no differences in N excreted in milk and urine between the 2 diets. The N retention and N excreted in feces were greater (P ≤ 0.038) for cows fed the SAIN diet.
Diurnal Patterns of HP, RQ, and CH4
Diurnal patterns of HP, RQ, and CH4 are shown in Figure 2. During the day, HP patterns did not differ (P ≥ 0.345) between the 2 diets at any time point. The CH4 production pattern for SAIN-fed cows was numerically lower between 2200 and 0600 h compared with CON-fed cows, with a significant (P = 0.002) effect observed at 2400 h. However, after the afternoon feeding, the CH4 production for SAIN-fed cows was numerically (P = 0.717) greater at 1800 h. The RQ pattern of the cows was greater (P < 0.0001) during the early morning at 0500 h and numerically greater (P ≥ 0.715) after the morning feeding (0700 to 1000 h), in the afternoon (1500 to 1700 h), and in the late evening (2100 to 2400 h) when fed the CON diet. As a result, the average of RQ tended (P = 0.066) to be greater for the CON diet than for the SAIN diet.
Figure 2Diurnal pattern of heat production, respiratory quotient (RQ), and CH4 production of dairy cows fed a TMR containing grass silage (CON; ○) or sainfoin silage (SAIN; ●). Arrows = feeding time.
We detected no significant differences in feed DMI of the cows when fed the 2 diets. However, due to compositional differences, ADF and N intake were greater for the SAIN diet. The average CT content in the 2 cultivars of sainfoin silage was 26.3 g/kg of DM, which resulted in a CT content in the SAIN diet of 8.8 g of CT/kg of DM. Substituting grass silage for sainfoin silage in the TMR of the cows fed at 95% of ad libitum did not reduce DMI in the present study. The palatability of the sainfoin silage was, therefore, at least comparable to that of the grass silage, and the intake of 8.8 g of CT/kg of DM did not affect DMI.
reported that DMI was not different in growing beef cattle fed a forage-based diet supplemented with quebracho tannin extract at levels of 0, 9, and 18 g of CT/kg of DM diet.
reported that consumption of Lotus pedunculatus with high CT contents (>50 g of CT/kg of DM) may negatively affect feed intake, whereas medium or low CT contents (<50 g of CT/kg of DM) seems to have no influence on feed intake by ruminants.
The apparent digestibility of DM, OM, NDF, and ADF was lower for the SAIN diet compared with the CON diet. This is in line with data reported by
, where apparent digestibility of OM, NDF, and ADF was lower for lambs fed sainfoin silage (containing approximately 5 g of CT/kg of DM) compared with lambs fed grass-clover (93.8% red clover and 6.2% white clover) silage.
also found numerically lower nutrient digestibilities in dairy cows fed grass and sainfoin hay compared with those fed only grass. Supplementation with tannin extract from quebracho trees to cattle (910 g of CT/kg of extract) at 9 and 18 g of CT/kg of DM diet had no effect on the apparent digestibility of DM, NDF, and ADF of the diet (
Effect of different levels of quebracho tannin on nitrogen utilization and growth performance of Najdi sheep fed alfalfa (Medicago sativa) hay as a sole diet.
reported decreased fiber digestibility in hay-fed rams at a quebracho dosage level of 22.5 g/kg of DMI. This shows that in addition to the CT content in the diet, the type of CT also contributes to effects on nutrient digestibility (
Interrelationships between the concentrations of total condensed tannin, free condensed tannin and lignin in Lotus sp. and their possible consequences in ruminant nutrition.
), thus preventing microbial digestion. Condensed tannins could also directly inhibit the cellulolytic microorganisms or activities of their fibrolytic enzymes (
). On the other hand, the lower DM, OM, NDF, and ADF digestibility for the SAIN diet might be explained in part by differences in the hemicellulose fraction [(NDF − ADF)/NDF] between diets, which was greater for the CON diet (40.18%) than for the SAIN diet (31.91%). Moreover, the ADL content of the SAIN diet (35.0 g/kg of DM) was greater than that of the CON diet (18.6 g/kg of DM).
reported that lignin is the major component in the cell wall limiting the digestibility of the cell wall polysaccharides in the rumen, by shielding the polysaccharides from microbial enzymatic hydrolysis. Although apparent digestibility of DM and OM was lower for the SAIN diet, the absolute amount of DM and OM digested did not differ between diet treatments. This could be explained by the numerical increase in DMI and OMI for the SAIN diet compared with the CON diet.
Milk Production
Milk yield of lactating ewes increased by 21% during mid to late lactation when the ewes were fed Lotus corniculatus containing 44.5 g of total CT/kg of DM diet, compared with ewes fed L. corniculatus in combination with polyethylene glycol (molecular weight of 3,500;
, who found that milk yields were greater on L. corniculatus (21.2 kg/cow per d) than on ryegrass (15.5 kg/cow per day), whereas there was no effect of intake. Similarly, in the current study, milk yield was 2 kg/cow per day greater for the SAIN diet even though feed intake and nutrients digested in absolute terms were similar between the 2 diets. A possible explanation could be that energy retention as body protein (ERp) of the cows when fed the SAIN diet was greater whereas energy retention as body fat (ERf) was lower when fed the SAIN diet (Table 5). This means that energy efficiency for production in cows fed the SAIN diet was greater than that in cows on the CON diet. During the measurement period in the CRC, all cows showed a minor loss of BW (−3.2 ± 0.69 kg; mean ± SEM) with no difference between the SAIN (average −3.0 kg) and CON (average −3.5 kg) diets. This would suggest that cows receiving the SAIN diet redirected more energy into milk rather than into the body tissue, especially in mid to late lactation, when cows are starting to deposit energy in the body, and this could be beneficial. Another aspect of the increase in milk production could be related to the sainfoin containing CT, which reduced protein degradation in the rumen, resulting in an increase in EAA available for absorption in the small intestine, as shown in previous studies (
). Therefore, increasing milk yield in our study could be due to increasing absorption of EAA in the small intestine. In future studies, it would be interesting to measure the effect of sainfoin on EAA supply in the small intestine.
Methane Production
The reduction in CH4 emissions observed in the current study could be explained by a decrease in fiber digestibility in the rumen, which agrees with the lower CH4 production. The products of fiber fermentation are acetate and butyrate, the biochemical pathways that liberate 2[H]− ions, and which are used in the rumen to produce CH4, whereas propionate production is considered as an H2 sink (
Methane production from in vitro rumen incubations with Lotus pedunculatus and Medicago sativa, and effects of extractable condensed tannin fractions on methanogenesis.
). In addition, the SAIN diet contained CT, which have been shown to reduce ruminal methanogenesis and decrease ruminal protozoa numbers in some studies (
Methane production from in vitro rumen incubations with Lotus pedunculatus and Medicago sativa, and effects of extractable condensed tannin fractions on methanogenesis.
Difference in the nature of tannins on in vitro ruminal methane and volatile fatty acid production and on methanogenic archaea and protozoal populations.
). In the current study, the CH4 emission per kilogram of FPCM was 15.81 and 14.36 g for the cows fed the CON and SAIN diets, respectively. These results are in line with those reported by
, who found that the CH4 emissions per kilogram of FPCM ranged from 14.6 to 17.4 g.
In our experiment, total daily CH4 emissions were similar between the 2 diets. However, cows fed the SAIN diet produced less CH4 per kilogram of DMI. These observations are in line with
, who compared the CH4 emission and milk yield in dairy cows fed either Hedysarum coronarium (CT-containing forage) or perennial ryegrass and found that CH4 emission per kilogram of DMI was lower in the cows fed H. coronarium. These results suggest that sainfoin could be an interesting roughage to be used in dairy cow diets as it resulted in CH4 emissions in the lower range compared with cows receiving grass silage or maize silage-based diets.
Energy Balance
The observed MEI:GEI ratio for the CON diet is in line with those reported by
, indicating that the animals received a diet of good quality. The SAIN fed cows had a 3.7-percentage-unit lower MEI:GEI ratio compared with CON, suggesting a slightly lower diet quality. The difference in MEI:GEI ratio between the 2 diets could be mainly ascribed to the decreased apparent energy digestibility (DEI:GEI, 73.0% for CON vs. 69.0% for SAIN) in the SAIN diet and to a somewhat lower metabolizability of the DEI (MEI:DEI, 87.0% for CON vs. 86.0% for SAIN). The energy retained (ER) in body mass was significantly greater in animals on the CON diet compared with the SAIN diet and considerably greater compared with studies of
. Those studies used dairy cows in mid lactation, whereas the animals in the current study were already in late lactation at the start of the experiment.
demonstrated that cows nearing the end of lactation start accreting more body fat relative to body protein. The CON diet animals showed that about 92% of the ER was related to ERf and 8% to ERp. In contrast, the SAIN diet showed that only 63.0% of ER was deposited as ERf and 37.0% to ERp, suggesting that metabolism in animals receiving the SAIN diet was redirected. A possible explanation could be that the CT in the SAIN diet modified the microbial profile or composition and microbial activity, resulting in more propionate than acetate. Acetate is an important precursor for fat metabolism (
Estimation of energy expenditure, net carbohydrate utilization, and net fat oxidation and synthesis by indirect calorimetry: Evaluation of errors with special reference to the detailed composition of fuels.
found that CT inhibited the growth of Butyrivibrio fibrisolvens, which are involved in fiber fermentation. The RQ tended to be greater for cows on the CON diet compared with cows on SAIN, which also indicates that nutrient metabolism could have differed between the 2 diets. The greater RQ for the CON-fed cows could be because the energy retained as body fat in these animals was greater than that of the SAIN-fed animals. In ruminants, lipogenesis mainly occurs in adipose tissue, for which acetate and butyrate are important precursors. Reducing equivalents (NADPH) needed for fatty acid synthesis come from glucose through the pentose phosphate cycle, a process that produces CO2 (
Estimation of energy expenditure, net carbohydrate utilization, and net fat oxidation and synthesis by indirect calorimetry: Evaluation of errors with special reference to the detailed composition of fuels.
). This means that the more fatty acids are synthesized, the more CO2 is produced, and, as a result, a greater RQ is obtained.
Nitrogen Balance
Nitrogen intake and N retention were greater on the SAIN diet, which could be related to the CP (171.9 g/kg of DM) in the SAIN diet, which was numerically greater than that of the CON diet (162.6 g/kg of DM). Improvement of N retention in cows fed the SAIN diet could be explained by content of CT, which reduces degradation of protein in the rumen and improves microbial protein synthesis (
The influence of addition of gallic acid, tannic acid, or quebracho tannins to alfalfa hay on in vitro rumen fermentation and microbial protein synthesis.
). The reduction of protein degradation in the rumen may occur due to the formation of tannin–protein complexes in the rumen pH and inhibition of the growth and activity of proteolytic bacterial populations (
Fecal N excretion also was greater for the SAIN diet, whereas we observed no difference in urinary N excretion between the 2 diets. These observations are in line with the study of
, who found that urinary N excretion was lower and feces N excretion was greater for lambs fed sainfoin silage compared with those fed grass-clover silage. Greater fecal N excretion has been reported in a study with CT-containing diets (
), where CT-protein complexes may not have been completely dissociated in the abomasum and lower digestive tract. Shifting the excretion pattern of N from urine to feces is beneficial to the environment because feces N is mainly in the organic form, which is less volatile compared with ammonia, whereas urinary N is more rapidly hydrolyzed to ammonia and nitrified to nitrate (
The inclusion of sainfoin silage in the diet of lactating dairy cows reduced nutrient digestibility and CH4 production per kilogram of DMI, while increasing milk production and improving N utilization. Moreover, inclusion of sainfoin silage in the diet resulted in greater efficiency with which ME intake was transformed into milk and energy retained in body protein. This suggests that sainfoin silage, or CT in sainfoin silage, affects metabolism and redirects it toward body protein accretion instead of body fat in late-lactation cows, resulting in leaner animals. Sainfoin silage has potential to be used in TMR for dairy cows to increase milk production.
Acknowledgments
The authors thank Bert Beukers, Willem van Ommeren, Teus Bleijenberg, and Ries Verkerk of the animal research facilities Carus of Wageningen University for their assistance with the dairy cow experiment; Stijn van de Goor for the technical assistance as part of his undergraduate course at Wageningen University, Wageningen, the Netherlands; Garry Waghorn (Dairy NZ, Hamilton New Zealand) for sharing his ideas on the urine collection device and views on tannin-related research; and Walter Gerrits (Animal Nutrition Group, Wageningen University, Wageningen, the Netherlands) for advice on the CRC data analyses. Irene Mueller-Harvey and Chris Drake (Reading University, Reading, UK) are acknowledged for the tannin analyses. This research was financially supported by European Union grant “LegumePlus” (PITN-GA-2011-289377). The authors report no conflicts of interest.
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