Environmental enrichment and its effect on the behavior of young pigs (sus scrofa) maintained in intensive housing

A major area of concern in the issue of animal welfare has always been that of animals in captivity. Restricting animals from engaging in behavior patterns which are considered "normal" for their species, as well as housing them in barren and unstimulating environments has been shown to increase the incidence of aberrant behavior and/or stress related problems (Newberry, 1988). This is particularly true in the livestock industry. Here, not only is the animal's welfare at stake, but the producer's welfare as well. These concerns have initiated studies into what, if any, benefit may be derived from the use of environmental enrichment for animals housed in captivity. This particular study examines that question with specific regard to intensively housed growing pigs.

Forty-eight Yorkshire sired cross-bred pigs were sorted by size and weight at weaning and placed into the nursery facility at the Knoxville Experiment Station, Louisville, Tennessee. They were separated into three treatment groups each containing 15 individuals. Treatment Boomer Balls®(BB), which was considered the "rooting group", received two heavy plastic Boomer Balls® per pen, each measuring 25.4 cm in diameter. Treatment Metal Chain(MC), the "oral group" was provided with three lengths of chain suspended from a notched 5.08 cm X 10.16 cm lumber which was suspended across the center of the pen. Each length of chain was 55 cm in length and there was approximately 20 cm distance between each chain. Treatment Control(C) was the control group and received no enrichment. All animals were provided a standard ration of 19% protein. Each pen had unlimited access to water from nipple waterers,

Animals were videotaped for 6 hours daily for 22 days. Enrichment was provided on an every other day basis. Behavioral observations were recorded on the target behavior patterns of aggression, play, abnormal behavior, exploratory behavior, resting behavior, and drinking behavior. An ethogram is provided. Behavioral data was analyzed on a pen by pen basis using a repeated measures technique.

The paired t-test for the comparison of means (days enriched vs. days not enriched) showed a significant effect of enrichment for 3 of 4 target behaviors in pen 1(88) (lower aggression, lower abnormal behavior, higher exploratory behavior). Pen 2 (BB) had a significant effect of enrichment on aggression (lower), abnormal behavior (lower), exploratory behavior (higher) and resting behavior (lower). Pen 3 (MC) had significant effects on aggression (lower) play (higher)abnormal behavior (lower), exploration (higher) and resting (lower). Pen 4 (MC),had a significant effect of treatment on resting behavior (lower)..

Analysis of variance showed a significant difference (average frequency/duration across entire study period) between the two treatment groups and the control group for the target behaviors of exploration and drinking. The"adjacent pen effect" is identified and discussed for its implications in future studies.