Effects of bovine somatotrophin (bST) on ovarian function in post-partum beef cows

Abstract

The effects of bovine somatotrophin (bST) on ovarian follicle development and function and associated gonadotrophin profiles during the first nine weeks post partum were investigated in beef cows. Thirty-two cows (Shorthorn x Galloway) in moderately low body condition (BC) at calving were fed to maintain BC thereafter. At Weeks 2, 4, 6 and 8 post partum, animals were injected with 320 mg bovine somatotrophin (bST) (T, treated; n = 17) or with the carrier oil only (C, control; n = 15). Ovulation occurred in 4 of 17 T cows and 0 of 15 C cows (P = 0.10) by nine week post partum. Treatment with bST did not affect the numbers of small (3-8 mm in diameter) or large (> 8 mm in diameter) follicles or the granulosa cell populations but enhanced the oestradiol (P < 0.05) and insulin-like growth factor-I (IGF-I) content (P < 0.01) of large follicles by nine weeks post partum. It did not significantly affect the testosterone concentrations of large follicles. Circulating concentrations of growth hormone (GH) and IGF-I were higher in T cows than in C cows (P < 0.001) but were unrelated to gonadotrophin profiles or gonadotrophin receptor concentrations in the follicles. At Week 8, plasma insulin concentrations were higher in T cows than in C cows both before (P < 0.05) and after (P < 0.05) glucose injection. It is concluded that GH may play an important role in mediating the effects of nutritional state on ovarian function during the postpartum period, possibly through alteration of intrafollicular IGF-I concentrations.

Resposta superovulatória de novilhas mestiças holandês-zebu tratadas com somatotropina bovina recombinante (rbST)

“…Os efeitos do rbST, via IGF-1, sobre a função ovariana também estão relacionados à potencialização (ERICKSON et al, 1989) e ao aumento da sensibilidade folicular às gonadotrofinas (GONG et al, 1996a;GONG e WEBB, 1996), além de modificar o padrão de aporte e utilização de nutrientes por tecidos dos órgãos genitais (PINTO ANDRADE et al, 1996).…”

Interaction between growth differentiation factor 9, insulin-like growth factor I and growth hormone on the in vitro development and survival of goat preantral follicles

“…Furthermore, GH has been shown to enhance cell proliferation and steroidogenesis of cultured granulosa cells in rats (21) and in cattle (22), pointing out an important role of this hormone in the regulation of follicular growth. Early studies assumed that IGF-I was the sole mediator of GH action in the ovary, since IGF-I or GH enhances steroid production to the same extent in rats (23) and GH usually increases follicular-luteal IGF-I in cows (24). Although some actions of GDF-9, GH and IGF-I on ovaries have been well analyzed in some mammalian species, little is known about their interaction on the development of goat preantral follicles.…”

Efeito da somatotropina na população folicular, recuperação de oócitos e produção in vitro de embriões em vacas Gir

“…Portanto, é possível que a proporção livre e ligada de IGF-1 possa diferir entre a raça Gir e as demais raças européias. Os efeitos da somatotropina sobre a função ovariana estão relacionados ao padrão de aporte e utilização de nutrientes por estes tecidos (Pinto Andrade et al, 1996). O tratamento com rbST exógeno estimula as concentrações séricas de IGF-1 e IGFBP-3, reduzindo a de IGFBP-2.…”