Effect of dietary fat supplementation on methane emissions from dairy cows fed wheat or corn

摘要

Diets that contain high proportions of either wheator supplementary fat have been individually reportedto reduce enteric methane production. The objective ofthis research was to determine the effect of dietary fatsupplementation on methane emissions and milk yieldfrom cows fed diets containing either corn or wheatgrains. It was hypothesized that cows fed a diet containingwheat would produce less methane and havelower methane yield (methane per kg of dry matterintake; MY) than cows fed a diet containing corn andthat methane mitigation from fat supplementationwould occur irrespective of the type of grain in thebasal diet. The experiment involved 32 Holstein-Friesiandairy cows allocated to 1 of 4 treatment groups(n = 8) and individually fed different diets restrictedto approximately 90% of their mean ad libitum intakemeasured during a covariate period. All animals wereoffered 11.5 kg of dry matter/d of alfalfa hay, 1.8 kg ofdry matter/d of solvent-extracted canola meal, and 1 of4 dietary supplements. Dietary supplements were 8 kgof dry matter/d of either corn or wheat, or these sametreatments with the addition of 0.8 kg of canola oil. Inthis 5-wk experiment, d 1 to 7 served as the covariateperiod, d 8 to 14 as the transition period, d 15 to 28as the adaptation period, and d 29 to 35 as the experimentalperiod. Cows were fed their full treatment dietsfrom d 15 to 35 during which time milk production andfeed intake were measured daily. During d 29 to 35,methane production was measured for individual cowsdaily using the sulfur hexafluoride tracer method. Theresulting averages for milk production and feed intakewere analyzed by analysis of covariance with factorialgrain by fat as treatment structure, animal as the unitwithin blocks, and the corresponding milk productionor feed intake covariate averages as principal covariate.Data on milk fatty acids, ruminal fluid data on pH, ammonia,volatile fatty acids, protozoa, and methane wereanalyzed by ANOVA using the same treatment andblocking structures excluding the principal covariate.Cows fed a diet containing wheat had greater MY thancows fed a diet containing corn. Irrespective of the typeof grain in the diet, increasing the fat concentrationfrom 2 to 6% dry matter reduced MY. It is concludedthat the grain component in the basal diet does notaffect the mitigating effects of dietary fat supplementson MY.