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