The effects of long-term administration of recombinant bovine somatotropin (Posilac) and Synovex on performance, plasma hormone and amino acid concentration, and muscle and subcutaneous fat fatty acid composition in Holstein-Friesian bull calves.

Abstract

The effect of recombinant somatotropin (rbST), Synovex (Syn), and their combination (rbST+Syn) on intact male calves was examined in an experiment that lasted an average of 238 d. Holstein-Friesian bull calves were allotted to one of four subtreatments (n = 14/treatment) in a factorial arrangement. There were two levels of rbST (0; rbST) and two levels of the estrogenic growth promoter Synovex (0; Syn). The rbST was administered once every 2 wk as injections of 500 mg of Posilac. Synovex (C and S) was implanted at 90-d intervals. The animals were fed for ad libitum consumption a diet with a metabolizable energy concentration of 11.7 MJ/kg DM and 15% crude protein. The hot carcasses were weighed after the removal of kidney, pelvic, and cod fats, which were weighed separately. The 12th rib cut was saved for analysis. Average daily gain and feed conversion efficiency were increased by rbST treatment by 9% (P < .005) and 10% (P < .016), respectively. There was no significant effect of Syn treatment, nor was there a rbST x Syn interaction. The proportion of the fat of the large depots in the carcass was reduced by 34% (P < .0001) and in the longissimus muscle by 32% (P < .16) owing to the rbST treatment. The plasma concentrations of GH, insulin, and thyroxin were increased by rbST treatment (P < .001, P < .01, and P < .03, respectively). The concentration of IGF-I was not affected. Synovex had no effect on plasma hormone concentration. Plasma essential and nonessential amino acid concentrations were reduced by 14 and 9%, respectively, when rbST was injected. Concentrations of cholesterol and fatty acids in muscle and subcutaneous fat were not affected (P > .072) by the rbST treatment. Synovex increased the monounsaturated fatty acids (MUFA), and the combinaton of Syn with rbST reduced polyunsaturated fatty acid (PUFA) concentration in the longissimus muscle (at the 12th rib). The reduced muscle fat content of the rbST-treated animals was associated with a trend toward an increase in polyunsaturated fatty acids.

Somatotropina bovina recombinante (rBST) sobre o desempenho e a digestibilidade aparente de novilhas (½ Nelore x ½ Red Angus) em confinamento

“…Early et al (1990), avaliando o efeito da aplicação de rBST em 20 novilhos, por um longo período (112 dias), não observaram diferença significativa para a IMS entre os animais controle (7,9 kg) e os que receberam 20,6 mg/dia de rBST (8,1 kg). Da mesma forma, Holzer et al (1999), trabalhando com machos inteiros e doses de 500 mg de rBST (Posilac®) a cada 14 dias durante 236 dias de experimento, não observaram influência sobre a IMS (8,7 kg para os animais tratados e 8,8 kg para os animais controle). No entanto, Rumsey et al (1996) observaram aumento de 2,3% na IMS para novilhos tratados com rBST em comparação com tratamento controle.…”

“…Entretanto, Vann et al (1998), avaliando a administração de rBST no aumento da massa muscular em bezerros em creep-feeding, observaram que os tratamentos com rBST não diferiram do controle para RC e para peso dos órgãos internos. Resultados semelhantes foram obtidos por Holzer et al (2000), trabalhando com bezerros Holstein-Friesian, administrando 500 mg de rBST (Posilac®) a cada 14 dias, durante 240 dias de experimento.…”

Subcutaneous fatty acid composition of steers finished as weanlings or yearlings with and without growth promotants

“…In contrast, other studies with estrogen-implanted bull calves [12] or steers [13] found reduced SFA and increased MUFA. In the same studies, Hozler et al [12] and Ibrahim et al [13] reported a decrease and an increase in the proportions of polyunsaturated FA (PUFA), respectively. In general, the available information on the effects of growth promoting implants on beef FA composition are inconclusive.…”

“…Regarding FA composition, studies with estrogen- or androgen-implanted steers showed small increases in the proportions of saturated FA (SFA) and decreases in proportions of monounsaturated FA (MUFA) [10,11]. In contrast, other studies with estrogen-implanted bull calves [12] or steers [13] found reduced SFA and increased MUFA. In the same studies, Hozler et al [12] and Ibrahim et al [13] reported a decrease and an increase in the proportions of polyunsaturated FA (PUFA), respectively.…”

Perfil metabólico de touros da raça Nelore (Bos taurus indicus) confinados e tratados com somatotrofina bovina recombinante (r-bST)

“…1 Os níveis plasmáticos de colesterol total não foram influenciados pela aplicação de r-bST em dose única ou a cada 14 dias, em novilhas meio-sangue Nelore x Red Angus (Prado et al, 2003). Holzer et al (1999), avaliando os efeitos da r-bST e progesterona + benzoato de estradiol, ao longo de 240 dias de experimento, em animais da raça Holandesa, não observaram diferença entre os tratamentos para as concentrações do colesterol total. Da mesma forma, Holzer et al (2000), trabalhando com dois níveis de energia na dieta e dois níveis de r-bST, administrados em intervalos de duas semanas, também não observaram diferença entre os tratamentos em relação às concentrações desse metabólito.…”