Reducing stress in piglets as a means of increasing production after weaning: administration of amperozide or co-mingling of piglets during lactation?

The aim of this experiment was to reduce piglet stress and improve performance following moving and mixing at weaning by use of the anti-aggressive drug amperozide and the practice of co-mingling piglets during lactation. Thirty-six piglets weaned at 29 days of age were allocated to a 2 X 2 factorial arrangement of treatments as follows: (1) injection of 1 ml amperozide or placebo (0 . 9% saline) at the time of weaning, and (2) co-mingling or no co-mingling of piglets from day 10 of lactation to weaning. At weaning all piglets were injected with phytohaemagglutinin or saline, their change in skin-fold thickness was measured 24 h later and behaviour was recorded every 5 min for the first 120 min after weaning. At 4 and 24 after weaning the depth and extent of injuries were recorded. Daily live-weight gain, apparent voluntary food intake and food conversion ratio were not improved (P > 0 . 05) by administration of amperozide or co-mingling of piglets during lactation. Cell-mediated immunity, as evidenced by a 0 . 17 proportional decrease (P <0 . 001) in skin-fold thickness following the injection of phytohaemagglutinin was decreased in piglets not given amperozide at weaning. Injection of amperozide caused a 0 . 26 proportional increase (P <0 . 001) in the amount of time piglets spent lying and caused piglets to display no interest in the feeder (P <0 . 002) in the first 2 h after weaning. Consequently piglets not given amperozide were more active, spent more time at the feeder and participated in more aggressive encounters (P <0 . 01). A significant interaction occurred between co-mingling and amperozide for mean injury score at both 4 (P <0 . 01) and 24 h (P <0 . 05) after weaning. When measured 4 h after weaning, co-mingling of piglets during suckling reduced mean injury score regardless of whether piglets were given amperozide or not at weaning. When piglets were not allowed to co-mingle during lactation, amperozide reduced mean injury score proportionately by around 0 . 44 (P <0 . 01) compared with piglets administered with saline. Despite the administration of amperozide and the practice of co-mingling mingling causing a reduction in stress and an improvement in welfare in this experiment, there was no beneficial effect on performance in the first 2 weeks after weaning.