Abstract #M300

# M300
Replacing conventional or brown midrib corn silage with brown midrib sudangrass silage in the diets of lactating dairy cows.
K. F. Kalscheur*1, G. E. Brink1, 1U.S. Dairy Forage Research Center, USDA-ARS, Madison, WI.

Forages that use less water, but are high in digestibility, are sought as alternatives to traditional forages such as corn silage. Brown midrib (BMR) sudangrass is an example of alternative forage for corn silage. The objective of this study was to evaluate whether BMR sudangrass silage (SS) can replace 2 types of corn silage with differing fiber digestibilities [conventional (CONV) or BMR corn silage (CS)] in the diets of lactating dairy cows. Forty-eight Holstein cows in mid- to late-lactation were assigned to 1 of 4 treatments in a randomized complete block design. Cows were fed a common covariate diet for 2 weeks followed by 8 weeks of experimental diets. Diets were formulated to contain 40% CS, 20% alfalfa silage, and 40% concentrate on DM basis. Sudangrass silage was included in experimental diets at either 0 or 10% of the diet DM replacing either 10% CONV or BMR CS. All other ingredients (high moisture corn, canola meal, roasted soybeans, soyhulls, and minerals and vitamins) were included equally for all diets. Cow was the experimental unit. Dry matter intake (DMI) averaged 25.2 kg/d and was not affected by the type of CS used nor by the inclusion of SS in the diets (P > 0.05). Similarly, milk production (averaged 40.0 kg/d) and was not affected by type of CS nor SS inclusion. Milk fat percentage increased 0.15% for cows fed the addition of 10% SS compared with cows fed 0% SS. Milk protein, lactose, and total solids percentage was not affected by dietary treatments. Milk protein yield was greater (0.054 kg/d; P = 0.03) for cows fed 0% SS compared with cows fed 10% SS. Because the dietary CP% was slightly greater for diets containing 10% SS compared with 0% SS (17.2 vs 16.2%), MUN responded similarly (11.1 vs. 9.6 mg/dL; P = 0.001). Energy-corrected milk (ECM) and feed efficiency (defined as ECM/DMI) was not affected by changes in diet because of similar intake and performance. Overall, the inclusion of 10% SS as a replacement for either CONV or BMR CS did not negatively affect lactation performance. BMR SS can be a successful replacement for CS where CS availability is limited.

Key Words: BMR sudangrass, corn silage, milk production