Metabolic hormones and reproductive function in cattle

Diets can alter the concentrations of circulating hormones such as insulin and IGF-I. Such responsive hormones are related directly to nutritional status and moreover, directly or indirectly, associated with reproductive function and fertility. Metabolic hormones are involved in follicular development, number and size of ovarian structures, circulating concentrations of steroid hormones, duration of estrus, steroidogenesis, ovulation and embryonic development. However, circulating metabolic hormones in excess, resulting from high dry matter/energy intake can also contribute to the reduction of oocyte and embryo quality. Although changes in dietary intake affect ovarian function in Bos taurus and Bos indicus cattle, it seems that overfeeding influences more profoundly oocytes/embryos from heifers and cows of Bos taurus than of Bos indicus breeds. There is also a distinct effect of nutrition on in vitro vs. in vivo embryo production, in which metabolic hormones seem to affect more the later stages of follicle development. Thus, this paper presents and discusses the results of some relevant studies on the role of feed intake and its association with metabolic hormones in bovine reproduction.