3 Changes in growth performance, feeding behaviors, and posture behaviors of growing pigs subjected to low-intensity heat stress

Abstract

Abstract This study was to determine the impact of low-intensity heat stress on frequency and duration of feeding, drinking, ventral lying, and lying lateral lying behaviors. Pigs (n = 64; 24.6 ± 3.7 kg BW) were housed four per pen in thermoneutral conditions (CON; 23.9 °C ± 2.5 °C) or constant high ambient temperatures (HS; 28.7 °C ± 1.3 °C) for 16 d, followed by thermoneutral conditions (24.4 °C ± 1.8 °C) for both groups through d 21, and subsequent heat stress (28.0 °C ± 3.0 °C) for both groups through d 30. Eight focal pigs (2 pens/treatment) were video-recorded on d 3, 6, 10, 13, 20, and 29 at three time periods (morning: 0600-0800, afternoon: 1200–1400, evening: 1800–2000). Heat stress reduced ADG (HS: 1.00 kg/d, CON: 1.13 kg/d; P = 0.020) from d 14 through d 21, tended to reduce ADFI (HS: 2.14 kg/d, CON: 2.24 kg/d; P = 0.085), and increased GF (HS: 0.62, CON: 0.52; P = 0.006) from d 1 through d 7. Surface body temperature from d 2 through d 15 was greater in HS than CON pigs (mean: 39.4 °C, 37.6 °C, respectively), and was lower on d 18 for HS than CON pigs (36.4 °C vs. 37.8 °C, respectively) and d 22 (38.6 °C vs 39.3 °C, respectively). A treatment x day x time interaction for feeding duration (P = 0.003) showed CON pigs spent longer at the feeder in the morning of d 6 than HS (22.70 min, 8.97 min, respectively), but CON spent less time than HS during d 6 evening (8.78 min, 19.57 min, respectively). HS pigs visited the feeder more frequently in the evening (14.4 bouts) than CON pigs (7.8 bouts; P = 0.029). Low-intensity heat stress negatively impacted performance and altered time of feeding duration and frequency, indicating feeding behavior may be a useful heat stress predictor.