Is social stress in pigs a detrimental factor to health and growth that can be avoided by amperozide treatment?

Abstract

Two trials were conducted, the first to determine the effect of amperozide, a novel psychotropic drug, when administered as a single intramuscular injection at the time of mixing on the agonistic behaviour and/or growth performance of previously unacquainted pigs, and the second to further investigate a possible cause for the observed effects on growth performance. In both trials the pigs were penned in groups of 10 animals. All calculations of the effects of treatment of fighting behaviour and weight gain were based on the pen as the experimental unit. Student's t-test was used to determine treatment differences. In Trial 1, 120 6-week-old pigs were used to investigate the effect of amperozide and azaperone on agonistic behaviour and performance. Fighting behaviour was quantified by counting bite and slash marks on each pig before mixing and at 8, 26 and 48 h after penning. Each pig was individually weighed on Days 0, 7, 14 and 21. Amperozide significantly reduced physical damage at each time point when compared with both azaperone-treated pigs and controls. On average, amperozide significantly improved weight gain in the 3-week study period by 0.9 kg compared with both the remaining treatment groups. In Trial 2, 80 4-week-old pigs allowed free access to creep feed were used to determine the effect of amperozide on weight gain and feed intake after weaning and mixing. Each pig was weighed individually on Days 0, 4, 7, 14 and 21. Amperozide significantly improved weight gain by 0.9 kg over the entire study period. Amperozide did not affect feed intake. In the control group, 4 pigs died from diarrhoea. We conclude that there is a causal association between social stress and gastrointestinal dysfunction and checks in growth rate following weaning and mixing pigs.