Bioscientifica Proceedings

The reproductive physiology of postpartum cows is different from that of heifers because of the combined effects of the past pregnancy and lactation. Neither lactation nor pregnancy has a major effect on postpartum fertility when calving is free from disease and lactation is moderate. Postpartum beef cows in good body condition have conception rates nearly equivalent to those of virgin heifers once their uteri are involuted and they initiate ovarian cycles. However, cows will ...

The fertility of dairy cows has declined worldwide and this change is surprising given the importance of good fertility to the dairy industry. The decline in fertility can be explained by management changes within the dairy industry and also negative genetic correlations between milk production and reproduction. Four primary mechanisms that depress fertility in lactaling cows are anovulatory and behavioral anestrus (failure to cycle and display estrus), suboptimal and irregula...

Growth hormone (GH) is a pituitary hormone that affects animal growth, metabolism, lactation, and reproduction. Many of the effects of GH are mediated by insulin-like growth factor I (IGF-I) which is synthesized in liver and ovary in response to GH. Insulin-like growth factor I synergizes with gonadotrophins (LH and FSH) to stimulate growth and differentiation of ovarian cells. There are species differences in the effects of GH in reproductive biology. In most species, ovarian...