Pituitary follicle-stimulating hormone and luteinizing hormone concentrations in pregnant and lactating pigs

The performance of sows and litters penned individually or grouped in late lactation

Piglets in litters reared in groups from 3 to 7 weeks of age weighed less at weaning (7 weeks) than piglets in which litters were penned individually. Some of the difference between the two management systems was created within the week after grouping. Grouping sows and their litters did not initiate oestrus in lactation. The subsequent litter size of the grouped sows was reduced but between-treatment differences for this trait failed to reach significance at the 5% level.

Reproductive physiology in the pig with special reference to early weaning

The object of this paper is to review some aspects of reproductive physiology in the pig, especially in relation to conditions after farrowing when reproductive ability is normally inhibited by lactation and suckling, and when weaning at different periods after parturition may have a profound influence on the chances of successful conception and pregnancy. In undertaking this review, however, it soon became clear that very few detailed experimental studies had been carried out in sows during the period immediately following parturition. It was considered best, therefore, to compare some of the situations which exist in pigs at other reproductive stages with what little is known about the sow at the post partum stage and during lactation.

The ontogeny of hypothalamic pituitary function in the pig. I. Pituitary LH and FSH in the fetus and neonate

Pituitaries were collected from fetal and postnatal pigs from day 55 p.c. until 6 weeks after birth at closely spaced intervals. LH and FSH in individual pituitaries were quantified by both homologous RIA and homologous RRA. No significant difference was found between results obtained by RIA and RRA. Both LH and FSH are first detected by RIA and RRA in the porcine fetal pituitary at 75 days p.c. Thereafter both LH and FSH pituitary content rises until term. LH pituitary concentration in both male and female fetuses and FSH pituitary concentration in males exhibit a peak just before birth. FSH pituitary concentration in females rises until birth and thereafter remains elevated. A statistically significant sex difference was found postnatally with regard to FSH content and concentration but not for LH.