Impact of ruminal pH on enteric methane emissions.

The objective of this study was to determine the impact of ruminal pH on methane (CH4) emission from beef cattle. Ruminal pH and CH4 data were generated in 2 experiments using 16 beef heifers offered high-forage (55% barley silage) or high-grain (92% concentrate; DM basis) diets. Both experiments were designed as a replicated 4 × 4 Latin square with 4 periods and 4 dietary treatments. Methane was measured over 4 consecutive days using open-circuit respiratory chambers with each chamber housing 2 heifers. The ruminal pH of individual heifers was measured using indwelling pH loggers. The mean ruminal pH and CH4 emission (g/h) of 2 heifers in every chamber were summarized in 30-min blocks. Even though rumen methanogens have been described to be inhibited by a pH < 6.0 in vitro, in vivo CH4-production rates (g/h) did not decrease when ruminal pH declined to threshold levels for subacute (5.2 ≤ pH < 5.5) or acute ruminal acidosis (pH < 5.2; P > 0.05). Daily mean CH4 emission (g/d) and ruminal pH were only mildly correlated (r2 = 0.27; P < 0.05), suggesting that additional factors, such as increased propionate formation or passage rate, account for the lower CH4 emissions from cattle fed high-grain as compared to high-forage diets. Lowering ruminal pH alone is, therefore, not an effective CH4-mitigation strategy. Mechanisms permitting methanogens to survive episodes of low-ruminal pH might include changes in community structure toward more pH-tolerant strains or sequestration into microenvironments within biofilms or protozoa where methanogens are protected from low pH.

Potential of milk fatty acid composition to predict diet composition and authenticate feeding systems and altitude origin of European bulk milk.

The aims of this work were to elucidate the potential of using milk fatty acid (FA) concentration to predict cow diet composition and altitude of bulk milk collected in 10 different European countries and to authenticate cow-feeding systems and altitude of the production area using a data set of 1,248 bulk cow milk samples and associated farm records. The predictions based on FA for cow diet composition were excellent for the proportions of fresh herbage [coefficient of determination (R2)=0.81], good for hay, total herbage-derived forages, and total preserved forages (R2>0.73), intermediate for corn silage and grass silage (R2>0.62), and poor for concentrates (R2<0.51) in the cow diet. Milk samples were assigned to groups according to feeding system, level of concentrate supplementation, and altitude origin. Milk FA composition successfully authenticated cow-feeding systems dominated by a main forage (>93% of samples correctly classified), but the presence of mixed diets reduced the discrimination. Altitude prediction reliability was intermediate (R2<0.62). Milk FA composition was not able to authenticate concentrate supplementation level in the diet (<58% of samples correctly classified). Similarly, the altitude origin was not successfully authenticated by milk FA composition (<76% of samples correctly classified). The potential of milk FA composition to authenticate cow feeding was confirmed using a data set representative of the diversity of European production conditions.

Enteric methane emission, diet digestibility, and nitrogen excretion from beef heifers fed sainfoin or alfalfa.

Effects of plant-bound condensed tannin (CT)-containing sainfoin vs. CT-free alfalfa (or low-CT alfalfa-sainfoin mixture), plant stage of maturity, and their interaction on enteric methane (CH4) emissions, diet digestibility, and N excretion were studied, using 8 ruminally cannulated beef heifers in 2 sequential short-term experiments (Exp. 1 and 2). In Exp. 1, first growth legumes were harvested daily and offered fresh to heifers. Heifers were assigned to 100% sainfoin or 80% alfalfa:20% sainfoin (as-fed basis). Responses were measured at early (late vegetative to early bud; stage 2 to 3) and late (early flower; stage 5) stage of maturity. In Exp. 2, the same legumes were harvested from second growth (late bud; stage 4) and offered to heifers as hay; 100% sainfoin or 100% alfalfa. In both experiments, heifers were fed once daily at 1× maintenance. When fed as fresh forage (Exp. 1), sainfoin, compared with the alfalfa-sainfoin blend, had greater digestibility of OM (74.7 vs. 70.9%; P = 0.02), yet tended to have lower CP digestibility (73.2 vs. 77.1%; P = 0.059). There was no difference between fresh legumes for CH4 emissions [25.9 g/kg DMI ± 4.02 SE; 8.5% of gross energy intake (GEI) ± 1.26 SE; or 36.8 g/kg digested OM ± 1.75 SE]. The fresh legumes were more digestible at early, rather than at late, maturity and, consequently, enteric CH4 (27.4 vs. 24.4 g/kg DMI; P < 0.004; 8.9 vs. 8.1% GEI; P < 0.008) was greater at early, rather than at later, growth. When fed as hay (Exp. 2), sainfoin, compared with alfalfa, had greater digestibility of OM (60.5 vs. 50.3%; P = 0.007), lower digestibility of CP (64.2 vs. 68.8%; P = 0.004), yet there was no difference between the legume hays for CH4 emissions (22.4 g/kg DMI ± 1.29 SD and 7.1% GEI ± 0.40 SD). However, on the basis of OM digested, CH4 emissions were lower for sainfoin than alfalfa hay (44.3 vs. 59.0 g/kg; P = 0.008). Percentage of total N excretion in urine was less for sainfoin compared with alfalfa, both for fresh legumes in Exp. 1 (74 vs. 78%; P = 0.017) or hay in Exp. 2 (64 vs. 72%; P < 0.001), and increasing maturity lowered urinary N excretion. In conclusion, feeding CT-containing sainfoin partially shifted N excretion from urine to feces, but it had little impact on enteric CH4 emissions from beef cattle fed at maintenance as compared with feeding either 80% alfalfa:20% sainfoin (fresh forages) or 100% alfalfa (hay). Feeding fresh legumes harvested between the late vegetative to early bud stage, compared with harvested at the early flower stage, increased N excreted in urine as well as enteric CH4 emissions from beef cattle fed at maintenance.

Prediction of bulk milk fatty acid composition based on farming practices collected through on-farm surveys.

The aim of this study was to predict the fatty acid (FA) composition of bulk milk using data describing farming practices collected via on-farm surveys. The FA composition of 1,248 bulk cow milk samples and the related farming practices were collected from 20 experiments led in 10 different European countries at 44°N to 60°N latitude and sea level to 2,000 m altitude. Farming practice-based FA predictions [coefficient of determination (R(2)) >0.50] were good for C16:0, C17:0, saturated FA, polyunsaturated FA, and odd-chain FA, and very good (R(2) ≥0.60) for trans-11 C18:1, trans-10 + trans-11 C18:1, cis-9,trans-11 conjugated linoleic acid, total trans FA, C18:3n-3, n-6:n-3 ratio, and branched-chain FA. Fatty acids were predicted by cow diet composition and by the altitude at which milk was produced, whereas animal-related factors (i.e., lactation stage, breed, milk yield, and proportion of primiparous cows in the herd) were not significant in any of the models. Proportion of fresh herbage in the cow diet was the main predictor, with the highest effect in almost all FA models. However, models built solely on conserved forage-derived samples gave good predictions for odd-chain FA, branched-chain FA, trans-10 C18:1 and C18:3n-3 (R(2) ≥0.46, 0.54, 0.52, and 0.70, respectively). These prediction models could offer farmers a valuable tool to help improve the nutritional quality of the milk they produce.

Effect of dried distillers grains plus solubles on enteric methane emissions and nitrogen excretion from growing beef cattle.

The objectives of this study were to examine the impact of corn- or wheat-based dried distillers grains with solubles (CDDGS or WDDGS) on enteric methane (CH4) emissions from growing beef cattle and determine if the oil in CDDGS was responsible for any response observed. Effects of CDDGS or WDDGS on total N excretion and partitioning between urine and fecal N were also examined in this replicated 4 × 4 Latin square using 16 ruminally cannulated crossbreed heifers (388.5 ± 34.9 kg of initial BW). The control diet contained (DM basis) 55% whole crop barley silage, 35% barley grain, 5% canola meal, and 5% vitamin and mineral supplement. Three dried distillers grains with solubles (DDGS) diets were formulated by replacing barley grain and canola meal (40% of dietary DM) with CDDGS, WDDGS, or WDDGS plus corn oil (WDDGS+oil). For WDDGS+oil, corn oil was added to WDDGS (4.11% fat DM basis) to achieve the same fat level as in CDDGS (9.95% fat DM basis). All total mixed diets were fed once daily ad libitum. Total collection of urine and feces was conducted between d 11 and 14. Enteric CH4 was measured between d 18 and 21 using 4 environmental chambers (2 animals fed the same diet per chamber). Methane emissions per kilogram of DM intake (DMI) and as percent of GE intake (GEI) among heifers fed WDDGS (23.9 g/kg DMI and 7.3% of GEI) and the control (25.3 g/kg DMI and 7.8% of GEI) were similar (P = 0.21 and P = 0.19) whereas heifers fed CDDGS (21.5 g/kg DMI and 6.6% of GEI) and WDDGS+oil (21.1 g/kg DMI and 6.3% of GEI) produced less (P < 0.05) CH4. Total N excretion (g/d) differed (P < 0.001) among treatments with WDDGS resulting in the greatest total N excretion (303 g/d) followed by WDDGS+oil (259 g/d), CDDGS (206 g/d), and the control diet (170 g/d), respectively. Compared with the control diet, heifers offered WDDGS, CDDGS, and WDDGS+oil excreted less fecal N (P < 0.001) but more (P < 0.001) urinary N. Results suggest that high-fat CDDGS or WDDGS+oil can mitigate enteric CH4 emissions in growing beef cattle. However, to completely assess the impact of DDGS on greenhouse gas emissions of growing feedlot cattle, the potential contribution of increased N excretion to heightened NH3 and nitrous oxide emissions requires consideration.

Effects of increasing concentrations of glycerol in concentrate diets on nutrient digestibility, methane emissions, growth, fatty acid profiles, and carcass traits of lambs.

Two experiments were conducted to evaluate the effects of increasing concentrations of glycerol in concentrate diets on total tract digestibility, methane (CH4) emissions, growth, fatty acid profiles, and carcass traits of lambs. In both experiments, the control diet contained 57% barley grain, 14.5% wheat dried distillers grain with solubles (WDDGS), 13% sunflower hulls, 6.5% beet pulp, 6.3% alfalfa, and 3% mineral-vitamin mix. Increasing concentrations (7, 14, and 21% dietary DM) of glycerol in the dietary DM were replaced for barley grain. As glycerol was added, alfalfa meal and WDDGS were increased to maintain similar concentrations of CP and NDF among diets. In Exp.1, nutrient digestibility and CH4 emissions from 12 ram lambs were measured in a replicated 4 × 4 Latin square experiment. In Exp. 2, lamb performance was evaluated in 60 weaned lambs that were blocked by BW and randomly assigned to 1 of the 4 dietary treatments and fed to slaughter weight. In Exp. 1, nutrient digestibility and CH4 emissions were not altered (P = 0.15) by inclusion of glycerol in the diets. In Exp.2, increasing glycerol in the diet linearly decreased DMI (P < 0.01) and tended (P = 0.06) to reduce ADG, resulting in a linearly decreased final BW. Feed efficiency was not affected by glycerol inclusion in the diets. Carcass traits and total SFA or total MUFA proportions of subcutaneous fat were not affected (P = 0.77) by inclusion of glycerol, but PUFA were linearly decreased (P < 0.01). Proportions of 16:0, 10t-18:1, linoleic acid (18:2 n-6) and the n-6/n-3 ratio were linearly reduced (P < 0.01) and those of 18:0 (stearic acid), 9c-18:1 (oleic acid), linearly increased (P < 0.01) by glycerol. When included up to 21% of diet DM, glycerol did not affect nutrient digestibility or CH4 emissions of lambs fed barley based finishing diets. Glycerol may improve backfat fatty acid profiles by increasing 18:0 and 9c-18:1 and reducing 10t-18:1 and the n-6/n-3 ratio.

Effect of silage botanical composition on ruminal biohydrogenation and transfer of fatty acids to milk in dairy cows.

Ruminal biohydrogenation and transfer of fatty acids (FA) to milk were determined for 4 silages with different botanical compositions using 4 multiparous Norwegian Red dairy cows [(mean ± SD) 118 ± 40.9 d in milk, 22.5 ± 2.72 kg of milk/d, 631 ± 3.3 kg of body weight, 3.3 ± 0.40 points on body condition score at the start of the experiment] fitted with rumen cannulas. Treatments consisted of 4 experimental silages: a mix of the first and third cut of organically managed short-term grassland with timothy (Phleum pratense L.) and red clover (Trifolium pratense L.; 2 yr old; ORG-SG); organically managed long-term grassland with a high proportion of unsown species (6 yr old; ORG-LG); conventionally managed ley with perennial ryegrass (Lolium perenne L.; CON-PR); and conventionally managed ley with timothy (CON-TI). The herbages were cut, wilted, and preserved with additive in round bales and fed at 0.90 of ad libitum intake. A barley (Hordeum vulgare L.) concentrate constituted 300 g/kg of dry matter of the total feed offered. A Latin square design (4 × 4) with 3-wk periods and the last week in each period used for sampling was implemented. Omasal flows of FA were measured using Yb acetate, Cr-EDTA, and the indigestible neutral detergent fiber fraction as indigestible markers. The composition of FA was analyzed in feed, omasal digesta, and milk. Compared with ORG-LG, ORG-SG had a higher herbage proportion of red clover (0.36 vs. 0.01) and lower proportions of timothy (0.42 vs. 0.18), smooth meadowgrass (Poa pratensis L.), meadow fescue (Festuca pratensis Huds.), white clover (Trifolium repens L.), dandelion (Taraxacum spp.), and creeping buttercup (Ranunculus repens L.). The silages were well preserved. The concentration of neutral detergent fiber was higher and the concentration of Kjeldahl-N was lower for CON-TI than for the other silages. Silage type had no effect on dry matter intake, but milk yield was lower for CON-TI than for the other silages. Apparent biohydrogenation of C18:3n-3 was lower for ORG-SG (932 g/kg) than for ORG-LG (956 g/kg), CON-PR (959 g/kg), and CON-TI (958 g/kg). Compared with the grass-based silages, ORG-SG and ORG-LG resulted in higher omasal flows of C18:1 trans FA and higher milk fat proportions of C18:1 trans FA and C18:2 cis-9,trans-11. Apparent recovery of C18:3n-3 in milk was higher for ORG-SG (61 g/kg) than for ORG-LG (33 g/kg), CON-PR (34 g/kg), and CON-TI (38 g/kg), and milk fat proportion of C18:3n-3 was higher for ORG-SG than for CON-TI. Milk fat proportions of C16:0 were lower for ORG-SG and ORG-LG compared with those for CON-PR and CON-TI. It was concluded that high proportions of red clover and other dicotyledons in the silages affected ruminal biohydrogenation and increased milk fat proportions of beneficial FA.

The effect of excess cobalt on milk fatty acid profiles and transcriptional regulation of SCD, FASN, DGAT1 and DGAT2 in the mammary gland of lactating dairy cows.

The main objective of this study was to investigate the effect of excess cobalt (Co) on gene expression of stearoyl-CoA desaturase (SCD), fatty acid synthase (FASN), diacylglycerol acyltransferase 1 (DGAT1) and diacylglycerol acyltransferase 2 (DGAT2) of lactating dairy cows in relation to milk fatty acid profile. Seven multiparous cows of the Norwegian Red cattle breed (NRF) had their basal diet supplemented with 1.4 g Co as a 24 g/l solution of Co-acetate per os twice daily for 7 days followed by a 9-day depuration period. Udder biopsies were performed prior to the treatment period, after 1 week of treatment and immediately after the depuration period. Excess Co reduced the proportion of all cis-9 monounsaturated fatty acids and increased the proportion of 18:0 in milk. However, gene expression levels of SCD, DGAT1, DGAT2 and FASN were not significantly altered. Our results indicate that the effect of Co on milk fatty acid profile is mediated at the post-transcriptional level by reduced activity of SCD in the mammary gland. Potential mechanisms explaining how Co might reduce stearoyl-CoA desaturation are discussed.

Cobalt reduces the Δ9-desaturase index of sow milk.

The main objective of this study was to examine if cobalt (Co) reduces Δ(9) -desaturase indices in milk and blood lipids in sows. The experimental design consisted of a repeated measurement consisting of a pre-treatment period of a minimum of 9 days, a treatment period of 5 days and a post-treatment period of 6 days. Experimental animals consisted of 10 lactating sows; five sows had an intramuscular injection of 59 mg Co diluted in 5 ml 0.9% saline solution twice a day, whereas the other five had an intramuscular injection of 5 ml 0.9% saline solution twice a day as a control. Milk Δ(9) -desaturase indices for cis-9 18:1, cis-9 16:1 and cis-9 14:1 were significantly reduced (p < 0.0001) as a result of the Co-treatment, contrasting with the plasma Δ(9) -desaturase indices, which were unaffected. Potential mechanisms explaining how Co might reduce milk Δ(9) -desaturase indices are discussed. Moreover, the toxicological level of Co and potential implications of using Co-ethylenediaminetetraacetic acid as a liquid marker in digestibility experiments are addressed.

Intravenous injections of cobalt reduce fatty acid desaturation products in milk and blood of lactating cows.

The objective of this study was to determine whether intravenous infusion of Co affects levels of fatty acid desaturation products in bovine milk. Six cows were assigned to two replicated 3 × 3 Latin squares with 14-day periods. Treatment occurred on days 1 to 5 and depuration occurred on days 6-14. Two treatments were tested, the first consisting of per os supplementation of 3.5 g Co daily in the form of Co acetate and the second consisting of intravenous injection of 175 mg Co daily in the form of Co acetate diluted in saline solution. The third treatment was a control. Both Co treatments decreased cis-9 18:1 levels from approximately 18 to 14 g/100 g fatty acids, and increased 18:0 levels from 11 to 17 g/100 g fatty acids in milk fat (p < 0.001). The proportions of cis-9 10:1, cis-9 12:1, cis-9 14:1, cis-9 16:1 and cis-9 17:1 decreased (p < 0.001), whereas 17:0 and trans-11 18:1 increased (p < 0.001). In blood plasma, levels of cis (6,9,12) 18:3 (p < 0.001) and cis (8,11,14,17) 20:4 (p = 0.008) decreased after both the Co treatments. It is concluded that intravenous supply of Co reduces levels of fatty acid desaturation products in both bovine milk and blood.

Cobalt supplied per os reduces the mammary Delta9-desaturase index of bovine milk.

Results indicated that the dual marker system of Yb-acetate and Co-EDTA supplied per os reduced the proportion of fatty acids in bovine milk that were products of Delta (9)-desaturase. To verify this effect and identify the responsible marker component, 18 cows (3 cows per treatment) were administered per os a 0.25-L solution of either Co-acetate, Co-EDTA, Co-EDTA + Yb-acetate, EDTA, Yb-acetate, or water twice daily for 5 d. The daily amounts of Co, Yb, and EDTA were, respectively, 3.50, 3.44, and 21.00 g per cow. Milk and blood were sampled and analyzed for content of fatty acids, and blood was sampled and analyzed for Co and cobalamin. Only solutions containing Co had a reducing effect (P < or = 0.01) on fatty acids that were products of Delta(9)-desaturase in milk--cis-9 10:1, cis-9 14:1, cis-9 16:1, cis-9, trans-11 18:2, and cis-9 18:1--with the exception of the solution containing Co-EDTA + Yb-acetate for cis-9 18:1. Of the substrate fatty acids of Delta (9)-desaturase, only 18:0 increased (P < 0.001) in all groups supplied with Co-containing solutions. Thus, Co had a reducing effect (P < or = 0.004) on the Delta (9)-desaturase indices [(product of Delta(9)-desaturase)/(product of Delta(9)-desaturase + substrate of Delta(9)-desaturase)] of milk for cis-9 14:1, cis-9 16:1, cis-9 18:1, and cis-9, trans-11 18:2. There were no differences in Delta(9)-desaturase indices between Co-EDTA and Co-acetate. None of the marker solutions influenced the fatty acid composition of blood plasma, and Co was detected only in the blood samples from cows treated with solutions containing Co. On the basis of these results, we concluded that Co given per os decreased the Delta(9)-desaturase indices of bovine milk.

Technical note: assessment of recovery site of mobile nylon bags for measuring ileal digestibility of starch in dairy cows.

The objective of this study was to evaluate recovery site of mobile nylon bags for measuring ileal digestibility of ruminally undegraded starch in dairy cows. Eight feed samples of untreated and treated concentrates were examined. Three lactating cows equipped with rumen fistula and duodenal and ileal cannulas were used in the experiment. The mobile nylon bags containing intact feeds or residues after a 12-h ruminal incubation were pretreated using a 2-step procedure to simulate abomasal digestion before insertion through the duodenal cannula. To assess the effect of hindgut fermentation on starch digestibility, approximately half of the bags were collected from the ileum and half from the feces. The results indicate that feed samples should be preincubated in rumen before insertion into duodenum, and that samples with relatively high fractions of rumen-undigestible starch should be collected from the ileum instead of from feces.

Apparent ruminal degradation and rumen escape of lysine, methionine, and threonine administered intraruminally in mixtures to high-yielding cows.

We studied the kinetics of lysine, methionine, and threonine in six high-yielding dairy cows at peak lactation (stage 1) and 6 mo later (stage 2). The cows were fitted with cannulas in the rumen and duodenum and were automatically fed every 4th h. The three amino acids (AA) were administered intraruminally in mixtures at dosages of 100, 200, 300, and 400 mmol of each, together with polyethylene glycol (PEG) as a liquid marker. Mean rumen liquid pools at stages 1 and 2 were not significantly different. The mean liquid outflow decreased from 13.6 to 9.5 L/h, and there was a significant linear increase in the liquid outflow with increasing dosages of AA. No significant interaction was found between feeding levels and AA dosages on rates of apparent degradation and rumen escape values. Expressed as percentages of the dosage, all three AA studied showed a significant linear decrease in degradation and a significant increase in rumen escape values with increasing dosage. At the feeding levels in stages 1 and 2, the highest relative degradation rates (percentage of dosage) were observed for threonine. The relative degradation rate of methionine was significantly lower than of lysine at the high feeding level but significantly higher at the low feeding level. The mean rumen escape values of threonine, methionine, and lysine across dosages and feeding levels were 16.7, 22.1, and 20.5%, respectively. The flow of the administered AA into the duodenum during an 8-h period after administration increased with increasing dosages, with peak concentrations after 1 h. Thus, the amounts of rumen escape of the three AA were considerable at all dosages, even when the AA were administered in unprotected form.