Bioscientifica Proceedings

Summary. Studies of isolated cell types from sheep follicles revealed several functional changes which occur during follicular maturation. Cyclic AMP production by granulosa cells from the smallest follicles studied (1–3 mm diameter) was stimulated by FSH but not by hCG, suggesting functional FSH receptors at this early stage of differentiation. Medium-sized follicles (4–6 mm) responded to both FSH and hCG. Granulosa cells were unable to synthesize a...

Abstract unavailableKeywords: inhibin; oestradiol; cow; pig; FSH© 1991 Journals of Reproduction & Fertility Ltd...

Summary. The progress in understanding the metabolism of the ruminant cumulus-oocyte complex (COC) from large antral follicles has progressed significantly in the past decade. In particular, new insights in the importance of lipid metabolism, ß-oxidation and its relationship to oxidative phosphorylation within oocytes have emerged. This provides opportunities for tapping into the potential yield of ATP from lipid metabolism, as ATP content is a major dete...

Embryonic diapause was first identified over 150 years ago, but many questions still remain about how the external and hormonal controls of embryonic diapause translate into how the uterus conveys information to the embryo. Current evidence suggests that the control of diapause is mediated by components of the uterine secretions. However, the identity of the essential signalling molecule(s) is unknown. The mouse (Mus musculus), the mink (Neovison vison) and t...

Keywords: boar exposure; puberty; gilts; pheromones© 1990 Journals of Reproduction & Fertility Ltd...

The enhanced early embryonic survival in Chinese Meishan compared with Large- White gilts may be due, in part, to differences in ovarian and endocrine function, particularly during the periovulatory period. The overall patterns of oestradiol, LH and FSH secretion were not different between Meishan and Large-White hybrid controls during this period, although circulating inhibin concentrations were higher in Meishan gilts. Thus, there appeared to be a decreased sensitivity ...

Nutritional signals are detected by the central nervous system (CNS) and translated by the neuroendocrine system into signals that alter secretion of LH and growth hormone (GH). Furthermore, these signals directly affect the activity of the pituitary gland independently of CNS input. Insulin-like growth factor I (IGF-I), insulin, leptin and specific metabolites, such as glucose and free fatty acids (FFA)', are potential signals of the metabolic status to the brain-pituit...

The occurrence of puberty in the female is due to the interplay of central and peripheral mechanisms in which the hypothalamic-pituitary-ovarian axis regulates growth and gonadal function, as well as adipocyte hormone secretion. Hypothalamic GnRH mRNA expression increased at 3.5 months of age and declined by 6 months of age. Concomitant with the age related reduction in the oestrogen negative feedback on LH secretion was a decline in hypothalamic oestrogen receptor-&alph...

The components of ruminant seminal plasma and their influence on the fertility of spermatozoa are reviewed. Seminal plasma can both inhibit and stimulate sperm function and fertility through the multifunctional actions of organic and inorganic components. These effects are now better understood because the composition of the seminal plasma, including its protein content and that of other structures, specifically membrane vesicles, has been clarified. Spermatozoa gain motility ...

Abstract. The efficiency of milk production in pasture-based systems is heavily influenced by calving pattern, necessitating excellent reproductive performance in a short breeding season. Where grazed pasture is the major component of the diet, cows are underfed relative to their intake potential. A number of studies have identified body condition score measurements that are related to likelihood of both submission and conception. In general, fertility variabl...