A influencia da somatotropina bovina recombinante (rbST), aplicada um dia após o parto, sobre a produção e reprodução de vacas holandesas primíparas

Abstract

The objective of this study was to test the influence of a single application of rbST immediately post-calving on production and reproduction of primiparous holstein cows. A complete randomized design with two treatments (rbST, n=13 and control, n=13), was used. Milk-fat content, milk yield, body weight, body condition score, progesterone, intervals from calving to lst heat (ICH), and from calving to conception (ICC), number of services per conception and rate of conception at the lst service were studied. For control and rbST, respectively, ICH was 85.1 ± 11.5 and 65.5 ±11.5 days (P=0.24), ICC was 115.9 ± 12.6 and 82.2 ± 12.6 days (P=0.07), service per conception was 2.0 ± 0.3 and 1.3 ± 0.3 (P=0.15), and conception at first service 50 and 80% (P=0.16).There was a significant increase (P=0.04) in fat content in the first weeks, (P=0.01) on milk yield in the first week and (P=0.01) progesterone concentration on days 28 and 31 for rbST-treated animais. There were no effects (P=0.40) of rbST on body condition score and (P=0.46) body weight. It is concluded that: exogenous somatotropin soon after calving influenced reproduction and production of primiparous cows; rbST also influenced adipose tissue mobilization, in the first weeks after calving; the galactopoietíc effect of rbST was also shown in primiparous cows under negative energy balance. A single aplication of rbST 500mg was associated with corpus luteum function. Progesterone concentrations were higher in rbST cows which could explain improved reproductive traits.