Effect of dairy cow genotype and concentrate feed level on cow performance and enteric methane emissions during grazing
The current study (40 cows in a 2 × 2 factorial arrangement) compared methane (CH4) emissions from two dairy cow genotypes (Holstein-Friesian [HF], and Swedish Red × [Jersey × Holstein-Friesian] [Crossbred]) offered two levels of concentrate supplementation (3.0 or 6.0 kg/cow per day) while grazing. Enteric CH4 emissions were measured using the SF6 technique on three occasions over a 16 week period, while intakes were estimated using performance data. Increasing concentrate level increased milk and energy corrected milk (ECM) yields, had no effect on CH4 emissions (g day-1) and CH4 emissions per kg dry matter (DM) intake, while reducing CH4/ECM yield. Crossbreds produced milk with higher milk fat and protein contents than HF cows, but ECM yield did not differ between genotypes. Daily CH4 production (g day-1), and CH4 production per kg ECM yield was unaffected by genotype. Methane yield (g kg-1 DM intake) was higher with the Crossbred cows, although DM intake was estimated in this study, and this result should be interpreted with some caution. Thus HF and Crossbred cows had similar CH4 emissions.