Pen shape and size: effects on pig behavior and performance

Abstract

Crossbred growing pigs, with an average initial weight of 29.9 kg, were housed in groups of 15 in ten experimental pens (five shapes × two sizes) to assess the importance of pen shape in the perception of space quality. Pen sizes provided 0.396 and 0.356 m 2 per pig. In Experiment 1, four replications, each of a 4-week duration, were conducted comparing rectangular (length/width = 3), triangular (equilateral), square and circular pens. In Experiment 2, two replications, each of a 2-week duration, were conducted comparing altered circular (circular pen fitted with two 0.5 m interior walls) and square pens. Production parameters (Experiment 1 only), social behaviors, time budgets and space utilization were monitored for each pen of pigs. Weight gain, feed intake and feed efficiency in Experiment 1 averaged 623 g day −1, 1773 g day −1 and 0.353, respectively, and were not affected by pen shape or size. Post-mixing aggression was greater in circular pens than in square pens (34.6 vs 16.8 pig × s spent fighting per minute; P < 0.01) and intermediate in other shapes in Experiment 1. Levels of aggression in altered circular pens did not differ from that in square pens in Experiment 2. Pen shape did not affect levels of aggression or general activity (eating, drinking, standing, lying) in pigs 1 week later. In Experiment 1, pigs in small pens spent more time standing ( P < 0.05) and tended to have higher protest scores (open-mouthed attack not leading to shoulder pushing; P < 0.06) than pigs in large pens. Defecation areas in all shapes included corners, with pigs in circular pens apparently using feeder edges as corners. In altered circular pens, dunging areas included actual corners. Animals in triangular pens spent more time in quadrants (25% of pen area) containing pen walls ( P < 0.001) and less time in quadrants farthest from pen walls ( P < 0.001) than pigs in other shapes. Use of the quadrant of the pen containing pen corners did not differ with pen shape (excluding circles). Pigs in large pens spent more time in quadrants containing pen corners and less time in quadrants farthest from pen corners than pigs in small pens. Pigs in rectangular pens lay within 2.5 m of fewer pigs than pigs in other shapes ( P < 0.01). More small social groups (1–3 pigs) were formed in rectangular and square pens than in other shapes ( P < 0.01). In large pens, pigs formed more mid-size and fewer large social groups (7–9 pigs and 13–15 pigs, respectively) than in small pens ( P < 0.01).