Effects of nutrition and metabolic status on circulating hormones and ovarian follicle development in XXXX .

@entity8788 @entity22468 @entity4208 @entity53 @entity72261 @entity291 @entity413
Nutrition is a major factor affecting @entity291 reproductive efficiency. Long-term moderate or chronic dietary restriction results in a gradual reduction in dominant follicle (DF) growth rate, maximum diameter and persistence. Animals become anoestrus when they lose on average 22-24% of their initial body weight. There is evidence of significant animal-to-animal variation in the interval from the imposition of dietary restriction to onset of anoestrus and from the recommencement of re-alimentation to resumption of ovulation. In contrast, acute dietary restriction to 40% of maintenance requirements rapidly reduces dominant follicle growth rate and maximum diameter and induces anoestrus in a high proportion (60%) of heifers within 13-15 days of dietary restriction. In lactating dairy and beef @entity291 negative energy balance or reduced dietary intake in the early post-partum period, while not affecting the population of small-to-medium size follicles, adversely affects the size and ovulatory fate of the dominant follicle. Re-alimentation of nutritionally induced @entity22468 results in an initial gradual increase in dominant follicle growth rate and maximum diameter, followed by a more accelerated increase in dominant follicle growth rate and maximum diameter as the time of resumption of ovulation approaches. Increased dominant follicle growth rate and maximum diameter are associated with increased peripheral concentrations of @entity4208 , pulsatile LH and @entity53 . Direct nutritional effects on ovarian function appear to operate through hepatic rather than follicular regulation of @entity4208 , and on systemic concentrations of @entity8788 ; cumulatively reducing follicular responsiveness to LH and ultimately shutting down follicular @entity53 production. Indirect nutritional effects are apparently mediated through altering the GnRH pulse generator and in-turn selectively reducing pulsatile LH secretion without any apparent adverse effect on FSH secretory patterns. Endogenous opioid peptides, @entity72261 and @entity413 appear to play a role in the nutritional regulation of GnRH release and in turn pulsatile LH secretion.
