The effect of thermal environment and age on neonatal pig behavior.

Three experiments were conducted to evaluate the ability of a radiant environment and the presence of a littermate to attract pigs during the first 3 d of age. The effect of stimuli on pig movement was studied in an enclosed rectangular aluminum test chamber containing four similar sections that were heated independently. In Exp. 1, all sections were at 34.8 degrees C to evaluate the chamber for biases of where pigs located themselves at 1 (n = 24) and 2 d (n = 26) of age. More (P < .025) pigs settled (e.g., no movement for 7 min) in end sections than in middle sections. Age did not affect time to settle or settling location. The effect on pig location of heating one chamber end section to either 23, 40, 48, 56, or 64 degrees C and leaving the remaining sections unheated (24 degrees C) was determined in Exp. 2. Settling of pigs at 1 (n = 50) and 2 d (n = 50) of age was affected by temperature (P < .001) but not by age. The minimum distance between average pig location and the heated section occurred at 48 degrees C. Experiment 3 involved 15 pigs each at 1 and 3 d during a 1-h trial to compare the relative pig attraction to 1) a heated chamber end section at 44.4 degrees C when remaining sections were at 23.5 degrees C, 2) an anesthetized littermate in an end section when all sections were at 24.1 degrees C, or 3) a choice test involving a 45.5 degrees C end section and an anesthetized littermate in the opposite end section with three unheated sections at 23.7 degrees C. Average distance between the test animal and the heated section was greater (P < .01) than that between the test animal and an anesthetized pig. Pigs that were allowed a choice preferred to lie near an anesthetized littermate in a cold section rather than alone in a 45 degrees C section (P < .01), and they were less (P < .005) active when an anesthetized littermate was present in the chamber. Although radiant heat effectively attracted pigs, heat was less attractive than an anesthetized littermate. The greater attraction of pigs to a littermate than to radiant heat may explain why pigs remain near the sow and littermates during d 1 and 2 after birth.