Short Communication: Effect of Dietary Protein on Growth and Nitrogen Balance of Holstein Heifers

• Published in: Journal of dairy science 2001-04, Vol.84 (4), p.843-847
• Main Authors: Hoffman, P. C, Esser, N. M, Bauman, L. M, Denzine, S. L, Engstrom, M, Chester-Jones, H
• Format: Article
• Language: English
• Subjects: Albumins; Animals; Blood Proteins; Blood Urea Nitrogen; Body Composition; Cattle - growth & development; Cattle - metabolism; Dietary Proteins - administration & dosage; Dietary Proteins - metabolism; Feces - chemistry; Female; Nitrogen - analysis; Nitrogen - metabolism; Weight Gain - drug effects
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(01)74542-0

A growth study and a companion N balance study were conducted to evaluate the effect of dietary protein on growth and N utilization of postpubertal Holstein heifers. Forty heifers (398 +/- 9.4 kg) were fed one of four diets containing 8, 11, 13, or 15% crude protein (CP) for 121 d. Body measurements were taken at the beginning and end of the experimental period. Blood was collected via jugular vein every 28 d and evaluated for serum protein, albumin, and urea nitrogen. Curvilinear relationships were observed between dietary CP and gains in wither height and hip width, with maximal gains occurring at 13% CP. Feeding heifers higher amounts of dietary CP resulted in linear increases in heart girth gain, serum protein, albumin, and blood urea nitrogen. In the companion N balance study, feeding increasing amounts of dietary CP to heifers resulted in linear increases in N intake, fecal-N, urinary-N, and absorbed-N. There was a numerical trend towards maximal N retention in heifers fed diets containing 13% CP. Curvilinear relationships also were observed between dietary CP and dry matter, organic matter, and CP digestibility with maximal nutrient digestibilities occurring when heifers were fed diets containing 13% CP. Data suggest 13% dietary CP was optimal for postpubertal (400 kg) Holstein heifers.