Short communication: Effect of dietary protein on growth and nitrogen balance of Holstein heifers.
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.
Hoffman
P C
PC
Department of Dairy Science, University of Wisconsin, Madison 53706, USA. pchoffman@facstaff.wisc.edu
Esser
N M
NM
Bauman
L M
LM
Denzine
S L
SL
Engstrom
M
M
Chester-Jones
H
H
D000418:Albumins; D000818:Animals; D001798:Blood Proteins; D001806:Blood Urea Nitrogen; D001823:Body Composition; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005260:Female; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D015430:Weight Gain / Q000187:drug effects*
D000418:Albumins; D001798:Blood Proteins; D004044:Dietary Proteins; D009584:Nitrogen