title: Effect of total and rumen undegradable protein on the performance of cows fed low fiber diets.
abstract: Twelve multiparous and 18 primiparous Holstein cows were fed a 17.3% CP, 21.0% ADF diet during wk 2 through 6 postpartum. Cows then were assigned from wk 7 through 14 to one of three low fiber (10.7% ADF) dietary treatments containing either 14.4 or 18.7% CP, the latter with or without a soybean meal enhanced with rumen undegradable protein. Treatments had no effect on milk yield or composition in multiparous cows, although milk fat percentage was not depressed in multiparous cows receiving the low fiber diets. The soybean meal diet enhanced with rumen undegradable protein increased yields of milk, 4% FCM, fat, protein, and DMI compared with the 14.4% CP diet in primiparous cows; it also increased yields of 4% FCM and fat versus the 18.7% CP, untreated diet in primiparous cows. Blood urea N concentrations were greater for high CP diets than for the low CP diet in both parity groups. Rumen acetate: propionate ratios were higher for both high CP diets than for the low CP diet in multiparous cows. Soybean meal enhanced with rumen undegradable protein improved yields of milk and its components in primiparous cows fed low fiber diets, even when high protein diets were fed.
authors.affiliation: Department of Animal Science, North Carolina State University, Raleigh 27695-7621.
authors.forename: C A
authors.initials: CA
authors.lastname: Zimmerman
authors.forename: A H
authors.initials: AH
authors.lastname: Rakes
authors.forename: T E
authors.initials: TE
authors.lastname: Daniel
authors.forename: B A
authors.initials: BA
authors.lastname: Hopkins
mesh_terms: D000641:Ammonia / Q000032:analysis; D000818:Animals; D001806:Blood Urea Nitrogen; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D004043:Dietary Fiber / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D004435:Eating; D004734:Energy Metabolism; D005227:Fatty Acids / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005232:Fatty Acids, Volatile / Q000032:analysis; D005260:Female; D007774:Lactation; D008055:Lipids / Q000032:analysis; D008892:Milk / Q000032:analysis / Q000378:metabolism*; D011897:Random Allocation; D012417:Rumen / Q000737:chemistry
chemical_list: D004043:Dietary Fiber; D004044:Dietary Proteins; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D005232:Fatty Acids, Volatile; D008055:Lipids; D000641:Ammonia