Authors: VICTOR GONZALEZ-VIZCARRA, MARIA LOPEZ-SOTO, CAROLINA PUJOL-MANRIQUEZ, JESUS URIAS-ESTRADA, ALBERTO BARRERAS SERRANO, JOSE CALDERON-CORTES, GILBERTO LOPEZ-VALENCIA, FRANCISCO MONGE-NAVARRO, ALEJANDRO PLASCENCIA
Abstract: Twenty-one Holstein bull calves (368 ± 5.2 kg) were used in order to evaluate the effects of combining recombinant bovine growth hormone (bST) and anabolic implants on growth performance and dietary energetics. Steers were assigned (7 repetitions/treatment) to individual pens (16 m2) equipped with automatic waterers and 1.2 m fence-line feed bunks. The experiment lasted 56 days. Treatments were: 1) no bST, no implant; 2) implant; and 3) bST + implant. Compared to implanted cattle, the combination of exogenous bovine somatotropin and anabolic implants did not enhance growth performance or observed dietary energy. Compared to nonimplanted cattle, anabolic implants increased dry matter intake (DMI, 8.3%), average daily gain (ADG, 18.5%), gain efficiency (ADG:DMI; 7.9%), dietary net energy (6%), and apparent energy retention per unit of DMI (7%). Implantation reduced the estimated maintenance coefficients of intact Holstein calves by around 17%. The combinations of exogenous bovine somatotropin and anabolic implants did not enhance the growth performance or dietary energy of intact Holstein cattle fed a high-energy finishing diet.
Keywords: Growth promoters, Holstein calves, feedlot, performance, dietary energy
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