Effects of an opioid antagonist (naloxone) on reproductive function of multiparous sows

Abstract

72 multiparous Landrace × Large White sows were used to study the effects of naloxone on reproductive performance. 36 sows were injected i.m. with 200 mg of naloxone (1 mg/kg body weight) in saline solution daily for 3 days before weaning and on the day of weaning. 36 sows were injected with saline and kept as controls. The number of culled sows and sows with piglets that were weaned either at 21 or 28 days was significantly lower in the group treated with naloxone, as well as the interval to first fertile oestrus, for both lactation periods (21 and 28 days). The litter size at farrowing increased in groups treated with naloxone; the number of liveborn piglets increased and the number of stillborn piglets decreased.