Effects of oestrogen supplementation and space restriction on PGF2alpha-induced nest-building in pseudopregnant gilts.

摘要

This study examined the effect of oestrogen supplementation on PGF2alpha-induced nest-building in pseudopregnant gilts. Oestradiol valerate (5 mg/day) injections were given on days 11-15 of the oestrous cycle to induce pseudopregnancy. A further series of injections of either oestradiol valerate (5 mg/day) or vehicle were given on days 44-46 of pseudopregnancy to reflect more closely the hormone profile seen in pregnancy. Nest-building was induced by a single intramuscular injection of 15 mg of PGF2alpha (Lutalyse) on day 47 of pseudopregnancy. The gilts were housed in pens (2.8 X 1.7 m) containing straw in experiment 1 or were chronically confined in crates (0.6 X 1.7 m) that did not contain straw on days 44-48 of pseudopregnancy for experiment 2. Oestrogen-supplemented gilts had significantly higher concentrations of circulating 17beta-oestradiol on day 47 of pseudopregnancy, but there were no significant differences between treatments for circulating concentrations of prolactin, progesterone,cortisol or oxytocin, or for any behavioural measure in either experiment. The results indicate that there is no direct effect of supplementing already pseudopregnant gilts with oestradiol valerate on PGF2alpha-induced nest-building. The results also show that the prepartum environment has a pronounced effect on nest-building behaviours and that non-pregnant pigs might be a useful model for prepartum nest-building in this species.