Dose-response effects of recombinant bovine somatotropin implants on feedlot performance in steers.
Dalke B.S. | Roeder R.A. | Kasser T.R. | Veenhuizen J.J. | Hunt C.W. | Hinman D.D. | Schelling G.T.
One hundred twenty crossbred beef steers averaging 377 kg were used in a 2 X 4 factorial experiment to determine the dose-response effects of recombinant bovine somatotropin (rbST) implants on growth performance and carcass characteristics. The implant dosages were 0 (sham), 40, 80, or 160 mg/wk administered s.c. in the tailhead region on a weekly basis throughout the experiment. The steers were fed a high-concentrate diet, which contained either a degradable (DP; soybean meal) or an escape (EP; corn gluten and blood meal) protein source. No dietary protein effect or dietary protein X rbST level interactions were detected. Recombinant bST decreased both DMI (P < 0.10) and feed/gain (P < 0.05) in a linear dose-dependent manner. Dosage of rbST did not significantly affect (P > 0.10) ADG or final weight of the steers. Recombinant bST decreased backfat depth (P < 0.10), marbling score (P < 0.05), and quality grade (P <.0.10) and increased yield grade (P < 0.10) in a linear dose-dependent manner. Soft tissue composition of the 9-10-11th rib section was altered (P < 0.01) by rbST administration in a linear dose-dependent manner. The percentage of protein in the rib section was increased by 9.4% and fat was decreased by 11.8% at the 160 mg/wk rbST level compared with the sham-implanted steers. Recombinant bST did not affect (P > 0.10) dressing percentage, hot carcass weight, kidney, pelvic, and heart fat, or longissimus muscle area. Serum insulin-like growth factor I (IGF-I) concentrations in the steers exhibited a linear response to dosage of rbST (P < 0.01). These data indicate that rbST is an efficacious method of improving feedlot performance and partitioning nutrient deposition in feedlot steers.
Показать больше [+] Меньше [-]Ключевые слова АГРОВОК
Библиографическая информация
Эту запись предоставил Wolters Kluwer