The influence of pen size on toy preference of growing pigs

Abstract

Twenty-four crossbred gilts, averaging 4 weeks of age and 9.4 kg, were weighed and allotted to either a large pen with a space allowance of 0.8 m 2 per pig or a small pen with a space allowance of 0.4 m 2 per pig (12 gilts per pen). Pigs were offered four types of toys: (1) a knotted-rope (R) toy consisting of two 30.5 cm lengths of 1.27 cm diameter nylon rope tied in knots at both ends and in the center; (2) a 30.5 cm section of 1.27 cm diameter rubber hose (H); (3) a 30.5 cm long piece of brass-plated chain (C); (4) a Penn-Plax Plantation Rubber ™, hourglass-shaped, dog toy (D). Pigs were allowed 3 days to become acclimated to their surroundings prior to the introduction of the first toy. At 07:00 h on the morning of toy presentation, two identical toys were hung in each pen from the ceiling by elastic bungee cord. Play behavior was recorded by time-lapse video cameras for 12 h between 07:00 and 19:00 on each day of toy presentation. Play behavior consisted of a pig maintaining head contact with the toy for at least 10 s. Head contact included open-mouthed bites, any attempt to bite the toy, pushing/nudging the toy with the head or snout; and alertly following the toy followed by a bite, attempted bite, or push. After a 3-day period without toys, the next toy was presented to the pigs following the same procedure. This sequence of events continued until all toys had been presented to the pigs. Three days after the final toy presentation, all pigs were weighed, randomly reassigned to the two different pen sizes (12 pigs per pen), and presented with the same toys in a re-randomized order. The amount of time at least one pig in a pen played with a particular toy was recorded, as was the amount of time pigs spent on other activities, to ensure accurate measures of time. No significant ( P>0.15) pen size by toy interactions were identified; therefore, only main effect differences are reported. There was a trend for pigs in the large pen to play less ( P=0.08) than pigs in the small pen. Data indicated that pigs in the small pen group played with toys approximately 50 min more than pigs in the large pen group; however, the percentage of time spent playing with toys was unaffected ( P<0.10) by pen size. Pigs spent a greater ( P<0.05) amount of time playing with D than either R, H, or C. Moreover, pigs spent 18.96, 21.86, and 23.87% more ( P<0.05) time playing with D than R, H, and C, respectively. Pigs preferred ( P<0.05) or tended to prefer ( P≤0.12) D over other toys during the first 7 h of observation. During the eighth hour of observation, pigs spent significantly more ( P<0.05) time playing with D and R than H or C. We conclude that the addition of a soft, pliable, rubber dog toy enriches the environment of confined pigs, and could reduce or alter aggressive and stereotypic behaviors commonly associated with confinement operations.