EFFECTS OF BEET PULP AND ANIMAL BY-PRODUCTS ON MILK-YIELD AND IN-VITRO FERMENTATION BY RUMEN MICROORGANISMS

Forty-six Holstein cows (30 primiparous) were assigned to one of four dietary treatments arranged as a 2 x 2 factorial experiment during wk 4 to 17 of lactation. Main effects were com versus dried sugar beet pu lp and soybean meal versus animal by-product meal (mixture of meat and bone meal, feather meal, and blood meal). Beet pulp replaced half of the corn at 15% of dietary DM. Diet DM (mean of four treatments) conta ined 18% alfalfa pellets, 17.4% alfalfa hay, 17.2% corn silage, and 47 .1% concentrate. Milk yield did not differ among treatments (mean 32.0 kg/d). Dry matter intake, milk CP percentage, and milk CP yield decre ased 5.6, 3.7 and 5.2%, respectively, but milk fat percentage increase d 4.7% when beet pulp replaced com. Animal by-products did not affect DMI or milk fat, but milk CP percentage decreased 3.0%. The same diets were evaluated in a continuOus culture system. Fungal extract (Asperg illus oryzae), added as the third treatment, had little effect on ferm entation. Digestion of DM, OM, NDF, and ADF were not affected by dieta ry treatments. Molar proportion of acetate was greater when com was re placed by beet pulp. Although flow of NAN from fermenters increased by 3.2% with beet pulp and 3.1% with animal by-products, milk CP percent ages decreased.