Abstract #M281

# M281
Impact of dietary starch concentration formulated with two types of corn silage on methane and ammonia emissions in dairy cows.
J. I. Sanchez-Duarte*1, K. F. Kalscheur2, J. M. Powell2, 1South Dakota State University, Brookings, SD, 2US Dairy Forage Research Center, USDA, ARS, Madison, WI.

The objective of this study was to evaluate methane (CH4) and ammonia (NH3) emissions of lactating dairy cows fed different starch level and corn silage type. After the completion of an 8-wk production study, 48 Holstein cows were allocated to 1 of 4 air-flow controlled chambers (2 cows/chamber) for 6 d in a randomized complete block design. Chamber was the experimental unit. Cows were fed 1 of 4 diets arranged as a 2 × 2 factorial with 2 corn silage hybrids [conventional (CS) and brown midrib (BMR) corn silage] and 2 dietary starch concentrations (19 and 25% of DM). Performance data from the last 6 d and emission measurements last 3 d were recorded and used for analysis. Soyhulls and beet pulp replaced corn grain in the diet to decrease starch concentration. There was no effect of dietary starch concentration and corn silage on DMI, ECM, ECM/DMI, and milk protein percentage, however milk fat percentage was greater (P < 0.03) for cows fed diets formulated at 25% starch rather than diets with 19% starch. An interaction of silage × starch (P < 0.03) was observed for CH4 expressed as per unit of DMI and for MUN. Cows fed CS-25% starch had the lowest MUN. Cows fed BMR-25% starch produced 1.3 g CH4 less per unit of DMI than cows fed CS-25% starch, but were similar to cows fed 21% starch for any silage type. Emissions of CH4 and NH3 (g/d), and CH4/ECM did not differ among treatments. It was concluded that cows fed the BMR-25% starch have the potential to reduce CH4 emissions per unit of DMI even though productive performance was not improved. Table 1.
DMI, kg/d25.425.124.925.90.64NS
ECM, kg/d44.044.740.844.61.42NS
Fat, %3.914.073.684.020.11S
Protein, %
MUN, mg/dL11.9a10.8b11.2ab11.8ab0.37I
CH4, g/d503.0515.9494.0497.413.0NS
NH3, g/d22.727.623.423.12.65NS
abMean differences (P < 0.05). 1S = starch effect; I = silage by starch effect; NS = not significant.

Key Words: BMR corn silage, milk, gas emissions