Feeding Lactating Dairy Cows Proteins Resistant to Ruminal Degradation

Sixty multiprious Holstein cows were fed treatment diets from 11 to 40 d postpartum with corn silage as the forage. Treatment diets each contained a different supplemental protein: 1) solvent soybean meal; 2) extruded soy product; 3) combination of corn gluten meal and distillers dried grains with solubles; and 4) a combination of protein sources from diets 2 and 3. Covariate adjusted means for milk (kg/d) and milk fat (%) for treatments 1 through 4 were 37.5, 3.14; 38.5, 3.19; 31.8, 3.45; and 35.2, 3.08. Milk protein content and DM intake were greatest for cows fed diet 1.In a second trial, 105 multiparous Holstein cows 13 d postpartum were placed on 7 treatment diets for 60 d. Treatments 1 to 5 contained equal amounts of corn silage and alfalfa silage as forage sources and contained either: 1) solvent soybean meal; 2) roasted soybean meal; 3) roasted soybeans; 4) roasted soybeans and urea; or 5) a mixture of corn distillers dried grains and corn gluten meal. Treatments 6 and 7 had alfalfa silage as the forage source and either 6) solvent soybean meal or 7) roasted soybeans as the supplemental protein. Feeding roasted soybeans with the alfalfa silage-based diets increased milk 2.0 kg/d, 4% FCM 4.6 kg/d, and fat .23 kg/d when compared with solvent soybean meal. Milk protein production was depressed by feeding a combination of distillers dried grains and corn gluten meal when compared with feeding diets containing soybean sources with the corn silage-alfalfa silage diets. Resistant protein sources may have greater value with diets containing alfalfa silage than with diets containing corn silage.