The effect of environment enrichment on aggression in newly weaned pigs

Abstract

The effect of environment enrichment on aggressive behavior in newly weaned pigs was studied in two experiments. In the first experiment, 132 6-week old gilts were divided into two treatment groups and housed at 6 per pen. Into each pen was placed either a car tire suspended on a chain ∼ 15 cm above the floor or alternatively, no device at all (control). Between 11 and 12 weeks of age, time-lapse video tapes of animal behavior were recorded and an analysis revealed that pigs offered the tire and chain device displayed a lower frequency of total aggressive acts (948 for all pigs with tires per 24 h vs. 1107 for control pigs). Most notable was the reduced frequency of head to head knocks (64 for all pigs with tires per 24 h vs. 202 in controls ( P≤0.05)). In Experiment 2, 180 newly weaned pigs ∼ 28 days of age and equally represented by barrows and gilts were used. The pigs were assigned to one of three treatments at 15 per pen. The treatments were either: control (no device), a pacifier (sugar-mineral block suspended in a metal basket), or a teeter-totter (metal bar with rubber belts on the ends). Time-lapse video tapes were again collected on all pigs after a 7 day adjustment period. Analysis of these tapes again revealed that pigs offered a play device committed fewer total aggressive acts (46 per pig per 24 h in control vs. 22 per pig per 24 h in the teeter-totter group and 30 per pig per 24 h in the pacifier group, P≤0.01). This was particularly notable for the frequency of head to head and head to body knocks. These studies suggest that aggression frequency inintensively raised pigs can be modified by enriching their environment with play objects.