title: The effects of dietary crude protein level on rate, efficiency and composition of gain of growing beef bulls.
abstract: Two experiments were conducted to evaluate the effects of dietary CP level on rate, efficiency and composition of gain of growing beef bulls. In Exp. 1, 59 bulls (333 +/- 15.8 kg) were used. Eleven bulls were slaughtered on d 0 to provide an estimate of initial carcass composition (9-10-11 rib section chemical analyses), and remaining bulls were assigned to treatment diets containing 10, 12 or 14% dietary CP. Bulls fed the 10% CP diet grew slower (P less than .05) than bulls fed the 12 or 14% CP diets, although dry matter intake and feed-to-gain ratio did not differ. Bulls fed the 12% CP diet had fatter carcasses (P less than .05) than bulls fed the 10 or 14% CP diets and had greater daily fat accretion than bulls fed the 10% CP diet. In Exp. 2, 60 bulls (318 +/- 9.0 kg) were used. Bulls were assigned to initial slaughter (n = 6) or to one of three dietary treatments, 10, 12 or 14% CP, and were slaughtered after feeding for 66, 136 or 202 d (n = 6 . treatment -1 . slaughter time -1). Bulls fed 10% CP diets had lower (P less than .05) rates of carcass protein accretion during d 0 to 136 and d 0 to 202. Carcass fat gain was similar among treatments over the entire experiment, although bulls fed the 14% CP diet gained more fat during d 0 to 136 than bulls fed the other treatments.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Michigan State University, East Lansing 48824.
authors.forename: P T
authors.initials: PT
authors.lastname: Anderson
authors.forename: W G
authors.initials: WG
authors.lastname: Bergen
authors.forename: R A
authors.initials: RA
authors.lastname: Merkel
authors.forename: D R
authors.initials: DR
authors.lastname: Hawkins
mesh_terms: D000818:Animals; D001823:Body Composition / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects*; D002417:Cattle / Q000254:growth & development*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009751:Nutritional Requirements
chemical_list: D004044:Dietary Proteins