Effects of Reduced Nocturnal Temperature on Performance and Behavior of Nursery Pigs

Previous studies suggested that pigs prefer lower environmental temperatures during nighttime compared to daytime. So reducing nocturnal temperature in nursery barns may not jeopardize performance or welfare of pigs, but can save energy for heating the barn. A study was conducted to investigate growth performance and behavioral response of nursery pigs to reduced nocturnal temperature. This study was conducted in four replicates, each utilizing 270 newly weaned pigs and lasting for 5 wk. Temperature setpoint in the control room (CON) was started at 30°C and decreased by 2°C per week. In the treatment room (RNT), temperature setpoint was maintained same as in CON between 7:00 h and 19:00 h, and reduced by 8°C between 19:00 h and 7:00 h starting from d 5. Growth performance (15 pens/room, 9 pigs/pen, BW=(6.30.61) kg) was monitored for 5 wk, and behaviors in 6 pens in each room were video-recorded for 24 h 3 d after being exposed to the experimental temperature. Instantaneous scan sampling was performed to determine time budgets for standing, sitting, eating, drinking, belly nosing, three postures of lying, and huddling. Two focal pigs were continuously viewed to record duration and occurrence of eating and drinking. Reduced nocturnal temperature did not affect the growth performance of the pigs, time spent standing, sitting, total lying and eating or duration and frequencies of eating and drinking (all P>0.10). However, RNT increased time spent lying sternal (83 vs. 72%, P<0.001) and number of pigs that were huddling (70 vs. 50% of lying pigs, P<0.001), and decreased time spent lying laterally (0.8 vs. 4.6%, P<0.001), lying half laterally (5.3 vs. 11.0%, P<0.001), and belly nosing (0.9 vs. 1.7%, P=0.01) during nighttime. These results indicate that nursery pigs adopted the posture of lying sternal and huddled together to reduce heat loss from their body surface to maintain thermal balance and growth performance in RNT. Such mild reduction in nocturnal temperature in the nursery barn can save energy for heating the barn without negative effects on performance and behavior of nursery pigs.