Corn silage-based diet supplemented with increasing amounts of linseed oil: Effects on methane production, rumen fermentation, nutrient digestibility, nitrogen utilization, and milk production of dairy cows.

In this study, we assessed the effects of increasing amounts of linseed oil (LSO) in corn silage-based diets on enteric CH4 production, rumen fermentation characteristics, protozoal population, nutrient digestibility, N utilization, and milk production. For this purpose, 12 multiparous lactating Holstein cows (84 ± 28 d in milk; mean ± SD) fitted with ruminal cannula were used in a replicated 4 × 4 Latin square design (35-d period). The cows were fed ad libitum a total mixed ration without supplementation (control) or supplemented [on a dry matter (DM) basis] with LSO at 2% (LSO2), 3% (LSO3) or 4% (LSO4). The forage:concentrate ratio was 61:39 (on DM basis) and was similar among the experimental diets. The forage portion consisted of corn silage (58% diet DM) and timothy hay (3% diet DM). The proportions of soybean meal, corn grain and soybean hulls decreased as the amount of LSO in the diet increased. Daily methane production (g/d) decreased quadratically as the amount of LSO increased in the diet. Increasing LSO dietary supplementation caused a linear decrease in CH4 emissions expressed on either DM intake (DMI) basis (-9, -20, and -28%, for LSO2, LSO3, and LSO4, respectively) or gross energy intake basis (-12, -22, and -31%, for LSO2, LSO3, and LSO4, respectively). At 2 and 3% LSO, the decrease in enteric CH4 emissions occurred without negatively affecting DMI or apparent total-tract digestibility of fiber and without changing protozoa numbers. However, these 2 diets caused a shift in volatile fatty acids pattern toward less acetate and more propionate. The effect of the LSO4 diet on enteric CH4 emissions was associated with a decrease in DMI, fiber apparent-total-tract digestibility, protozoa numbers (total and genera), and an increase in propionate proportion at the expense of acetate and butyrate proportions. Methane emission intensity [g of CH4/kg of energy-corrected milk (ECM)] decreased linearly (up to 28% decrease) with increasing LSO level in the diet. Milk fat yield decreased linearly (up to 19% decrease) with increasing inclusion of LSO in the diet. Milk protein yield increased at 2% or 3% LSO and decreased to the same level as that of the nonsupplemented diet at 4% LSO (quadratic effect). Yield of ECM was unchanged by LSO2 and LSO3 treatments but decreased (-2.8 kg/d) upon supplementation with 4% LSO (quadratic effect). Efficiency of milk production (kg ECM/kg DMI) was unaffected by the 3 levels of LSO. Ruminal NH3 concentration was quadratically affected by LSO supplementation; decreasing only at the highest level of LSO supplementation. The amount (g/d) of N excreted in feces and urine decreased linearly and quadratically, respectively, as the amount of LSO increased in the diet, mainly because of the reduction in N intake. Efficiency of dietary N used for milk N secretion increased linearly with increasing LSO supplementation in the diet. We conclude that supplementing corn silage-based diets with 2 or 3% of LSO can reduce enteric CH4 emissions up by to 20% without impairing animal productivity (i.e., ECM yield and feed efficiency).

Methane emissions of manure from dairy cows fed red clover- or corn silage-based diets supplemented with linseed oil.

The objective of this study was to investigate the effects of forage source (red clover silage: RCS vs. corn silage: CS) and diet supplementation with linseed oil (LO) on CH4 emissions of manure from dairy cows. For this purpose, 12 lactating cows were used in a 2 × 2 factorial arrangement of treatments. Cows were fed (ad libitum) RCS- or CS-based diets (forage:concentrate ratio 60:40; dry matter basis) without or with LO addition (4% dry matter). Feces and urine were collected from each cow and mixed with residual sludge obtained from a manure storage structure. Manure was incubated for 17 wk at 20°C under anaerobic conditions (O2-free N2) in 500-mL glass bottles. Methane emissions and changes in chemical composition of the manure were monitored during the entire incubation period. The total amount of feces and urine excreted by cows was not affected by dietary treatments and averaged 6.6 kg/d of volatile solids (VS). Compared with manure from cows fed RCS-based diets, maximum CH4 production potential of manure from cows fed CS-based diets was 54% higher (182 vs. 118 L/kg of VS) throughout the incubation period. Maximum CH4 production potential from manure also increased (by 17%) when cows were fed LO-supplemented diets compared with those fed nonsupplemented diets. Similar to maximum CH4 production potential, VS degraded during incubation (i.e., VS loss) was higher from manure from cows fed CS-based diets versus cows fed RCS-based diets (30.6 vs. 22.5%), and increased (+3 percentage units, on average) with the addition of LO to the diets. Ammonia concentration in manure was higher when cows were fed CS-based diets compared with RCS-based diets, and declined with LO supplementation to CS and RCS diets. It is concluded that both dietary forage source and fat supplementation affect maximum CH4 production potential from manure and this should be taken into account when such dietary options are recommended to mitigate enteric CH4 emissions from dairy cows.

Linseed oil supplementation to dairy cows fed diets based on red clover silage or corn silage: Effects on methane production, rumen fermentation, nutrient digestibility, N balance, and milk production.

The objective of this study was to examine the effect of linseed oil (LO) supplementation to red clover silage (RCS)- or corn silage (CS)-based diets on enteric CH4 emissions, ruminal fermentation characteristics, nutrient digestibility, N balance, and milk production. Twelve rumen-cannulated lactating cows were used in a replicated 4×4 Latin square design (35-d periods) with a 2×2 factorial arrangement of treatments. Cows were fed (ad libitum) RCS- or CS-based diets [forage:concentrate ratio 60:40; dry matter (DM) basis] without or with LO (4% of DM). Supplementation of LO to the RCS-based diet reduced enteric CH4 production (-9%) and CH4 energy losses (-11%) with no adverse effects on DM intake, digestion, ruminal fermentation characteristics, protozoa numbers, or milk production. The addition of LO to the CS-based diet caused a greater decrease in CH4 production (-26%) and CH4 energy losses (-23%) but was associated with a reduction in DM intake, total-tract fiber digestibility, protozoa numbers, acetate:propionate ratio, and energy-corrected milk yield. Urinary N excretion (g/d) decreased with LO supplementation to RCS- and CS-based diets, suggesting reduced potential of N2O emissions. Results from this study show that the depressive effect of LO supplementation on enteric CH4 production is more pronounced with the CS- than with the RCS-based diet. However, because of reduced digestibility with the CS-based diet, the reduction in enteric CH4 production may be offset by higher CH4 emissions from manure storage. Thus, the type of forage of the basal diet should be taken into consideration when using fat supplementation as a dietary strategy to reduce enteric CH4 production from dairy cows.

Supplementation of increasing amounts of linseed oil to dairy cows fed total mixed rations: effects on digestion, ruminal fermentation characteristics, protozoal populations, and milk fatty acid composition.

The effect of linseed oil (LO) supplementation on nutrient digestibility, forage (i.e., timothy hay) in sacco ruminal degradation, ruminal fermentation characteristics, protozoal populations, milk production, and milk fatty acid (FA) profile in dairy cows was investigated. Four ruminally cannulated, primiparous lactating cows were used in a 4 × 4 Latin square design (28-d periods). They were fed a total mixed ration (50:50 forage:concentrate (F:C) ratio [dry matter (DM) basis] without supplementation (control, CTL), or supplemented (wt/wt; DM basis) with LO at 2, 3, or 4%. Supplementation with LO had no effect on DM intake (19 kg/d) and apparent total-tract digestibility of nutrients (organic matter, neutral detergent fiber, acid detergent fiber, starch, and gross energy). Ruminal pH, ammonia, and total volatile FA concentrations were not changed by LO supplementation to diets. Extent of changes in volatile FA pattern and effective ruminal degradability of DM of timothy hay were minor. Neither the total numbers nor the genera distribution of protozoa was changed by the addition of increasing amounts of LO to the diet. Milk yield increased linearly (26.1, 27.3, 27.4, and 28.4 kg/d for CTL to LO4, respectively) as the amount of LO added to the diet increased. Milk fat content was not affected by LO supplementation, whereas milk protein content decreased linearly with increasing amounts of LO in the diet. Milk fat proportions of several intermediates of ruminal biohydrogenation of polyunsaturated FA (i.e., trans-10 18:1, trans-11 18:1, cis-9,trans-11 18:2, trans-11,cis-15 18:2, and cis-9,trans-11,cis-15 18:3) increased linearly with LO addition to the diet. The proportion of cis-9,cis-12 18:2 decreased linearly (2.06, 1.99, 1.91, and 1.83% for CTL to LO4, respectively) as the amount of LO in the diet increased. Milk fat content of cis-9,cis-12,cis-15 18:3 increased as the level of LO in the diet increased up to 3% but no further increase was observed when 4% of LO was fed (0.33, 0.79, 0.86, and 0.86% for CTL to LO4, respectively). A similar quadratic response to LO supplementation was also observed for cis-5,cis-8,cis-11,cis-14,cis-17 20:5 and cis-5,cis-7,cis-10,cis-13,cis-16 22:5. The results of the present study show that LO can be safely supplemented up to 4% in forage-based diets of dairy cows to enrich milk with potential health beneficial FA (i.e., n-3 FA) without causing any detrimental effects on rumen function, digestion, and milk production.