Lactational performance, rumen fermentation and enteric methane emission of dairy cows fed high-amylase corn silage

The current study investigated the effect of a high-amylase corn silage on lactational performance, enteric methane (CH4) emission, and rumen fermentation of lactating dairy cows. Following a 2-wk covariate period, 48 Holstein cows were blocked based on parity, days-in-milk, milk yield (MY), and CH4 emission. Cows were randomly assigned to 1 of 2 treatments in an 8-wk randomized complete block design experiment: (1) control corn silage (CON) from an isogenic corn without a-amylase trait and (2) Enogen Feed Corn harvested as silage (ECS) containing a bacterial transgene expressing a-amylase in the endosperm of the grain. The ECS and CON silages were included at 40% of the dietary dry matter (DM) and contained 43.3 and 41.8% DM and (%, DM): neutral-detergent fiber, 36.7 and 37.5 and starch, 36.1 vs. 33.1, respectively. Rumen samples were collected from a subset of 10 cows using the ororuminal sampling technique on wk 3 of the experimental period. Enteric CH4 emission was measured using the GreenFeed system (C-Lock Inc, Rapid City, SD). Dry matter intake was similar between treatments. Compared with CON, MY (38.8 vs. 40.8 kg/d), feed efficiency (1.47 vs. 1.55 kg/d), and milk true protein (1.20 vs. 1.25 kg/d), and lactose yields (1.89 vs. 2.00 kg/d) were increased, whereas milk urea nitrogen (14.0 vs. 12.7 mg/dL) was decreased by ECS. There was no effect of treatment on energy corrected MY (ECM), but there was a trend for increased ECM feed efficiency (1.45 vs. 1.50 kg/kg) by ECS compared with CON. Daily CH4 emission was not affected by treatment; emission intensity was decreased by ECS (11.1 vs. 10.3 g/kg milk), but CH4 intensity on ECM basis was not different between treatments. Rumen fermentation, apart from a reduced molar proportion of butyrate by ECS (14.6 vs 11.3%, respectively), was not affected by treatment. Only minor effects of treatment on rumen microbes and milk fatty acid profiles were observed. Apparent total-tract digestibility of nutrients and urinary and fecal nitrogen excretions were not affected by ECS. Overall, ECS inclusion at 40% of dietary DM increased milk, milk protein, and lactose yields and feed efficiency and tended to increase ECM feed efficiency, but had no effect on ECM yield. The increased milk yield with ECS led to a decrease in enteric CH4 emission intensity, compared with the control silage.