Bioscientifica Proceedings

The control of reproduction in goats is interesting for technical reasons (synchronization of kiddings, adjustment to forage availability or to economy), and for genetic reasons (identification and dissemination of improved genotypes). The use of short-light rhythms leads to markedly increased production of semen per buck and prevents occurrence of a ‘resting’ season. Recent identification of a bulbourethral lipase in goat spermatozoa opens new perspectives in sperm ...

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...

Abstract unavailableKeywords: corpus luteum; sheep; protein kinase C; calcium; phosphoinositide turnover© 1991 Journals of Reproduction & Fertility Ltd...

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...

Reduced reproductive efficiency has been reported in high-producing dairy cows. Sources of reproductive inefficiency include decreased expression of estrus, increased diameter of the ovulatory follicle and reduced fertility when cows are inseminated after estrus, increased incidence of double ovulation and twinning, and increased pregnancy loss. To overcome some of these inefficiencies, reproductive management programs have been developed that synchronize ovulation and enable ...