Published online by Cambridge University Press: 02 September 2010
Two experiments were conducted to elucidate the effects of intra-muscular injection of oestradiol within 1 min of birth (experiment 1) or within 4h of birth (experiment 2) on piglet activity, growth and pre-weaning survival rate. In experiment 1, 248 piglets (25 litters) were alternately injected within litter at birth with either 1 ml peanut oil/saline solution or 0·1 mg oestradiol benzoate in this carrier solution. The subsequent behaviour, growth and survival of these piglets were recorded. Experiment 2 used 38 litters (385 piglets), these being treated by litter with either of the same two treatments as soon after birth as they were found (approx. range 0 to 4 h). Piglet survival data were collected from this field trial. Oestradiol treatment significantly reduced the intervals from birth to reaching the udder (596 v. 740 s, P < 0·05) and from birth to first sucking (1060 v. 1497 s, P < 0·01) relative to control piglets in experiment 1. Treatment had no significant effect on pre-weaning growth rate (experiment 1), but did tend to reduce early postnatal mortality rate in both experiment 1 (7·2 v. 2·4% for control and oestradiol-treated piglets respectively) and experiment 2 (13·0 v. 10·2% for control and oestradiol-treated piglets respectively). It is concluded that oestradiol treatment at, or soon after, birth induces short-term hyperactivity in piglets. This may subsequently be reflected in an improvement in pre-weaning survival rate of piglets, although further data are required to confirm this conclusion.