Effect of sensory stimuli on huddling behavior of pigs.

Two experiments involving pigs at 1, 3, and 8 d of age were conducted to 1) compare huddling between littermates and nonlittermates, 2) study the ability of pigs to distinguish an anesthetized piglet from a piglet-shaped object, and 3) explore the importance of physical contact between pigs on huddling behavior. Experiments were conducted in an enclosed rectangular aluminum test chamber having pressure sensors beneath floor panels to detect test pig location. Test objects were placed on a platform at one end of the chamber and test pig location was monitored during a 45 min trial. Experiment 1 involved a total of 45 pigs (5 pigs/treatment on d 1, 2, and 3). The results indicate that, regardless of age (P > .05), when either a littermate or a nonlittermate occupied the platform, average location of test pigs that "settled" (ceasing to move for 7 min or more) was closer to the platform (P < .01), time spent near the platform was greater (P < .01), and movement about the chamber was less (P < .01) than when the platform was empty. No differences (P > .05) were observed between littermate and nonlittermate stimuli for these variables. During Exp. 2, the platform was covered with wire mesh. A total of 98 pigs were used in the study. Treatments were a cage containing 1) no object (n = 24), 2) a wooden block (n = 25), 3) a pig-shaped latex casting (n = 24), or 4) an anesthetized 8- to 10-d-old pig (n = 25). Pig age and treatment did not affect the percentage of time in each trial that pigs spent within 23.5 cm of the cage or the percentage of pigs settling within 23.5 cm of the cage. These studies show that pigs huddle similarly with littermates and nonlittermates and that physical contact with another piglet but not visual recognition of another piglet affects piglet huddling.