Eight experiments were conducted to determine the effect of a single administration of
amperozide on agonistic behavior and growth performance in newly mixed, restricted-fed pigs. Two hundred 12-wk-old pigs were used in a 4-wk trial (Exp. 1) to investigate the effect of
amperozide on agonistic behavior and performance. The pigs were assigned to each pen on the basis of
body weight and sex, ensuring that pigs in each pen were unacquainted. Each pig was weighed individually on d 3, 7 and 28. Agonistic behavior was quantified by counting
bite and slash marks on each pig at 8, 26 and 48 h after penning. An i.m. injection of
amperozide immediately before mixing the pigs reduced the physical damage (P less than .001) at each time point. There was no evidence of
amperozide causing either sedation or motor disturbances. On the average,
amperozide treatment improved (P less than .001) daily gain in the 4-wk study period by 70
g (17%). In Exp. 2 to 8, 1,648 pigs growing from approximately 20 to 100 kg
body weight were used to determine the effect of
amperozide on
weight gain. Pigs were penned in groups of 9 to 11, randomly assigned to each pen on the basis of sex. Each pig was weighed individually after penning, on d 35 and at slaughter. Untreated control pigs had a poorer growth performance than did
amperozide-treated pigs. During the first 5 wk postpenning average daily gain was improved (P less than .001) by 90 g (26%) in pigs receiving a single
oral administration of
amperozide at penning.(ABSTRACT TRUNCATED AT 250 WORDS)