Feeding Behavior of Finishing Pigs under Diurnal Cyclic Heat Stress

SIMPLE SUMMARY: Pigs reared in tropical climate areas are frequently exposed to high ambient temperatures. The increase in ambient temperature above thermoneutrality evokes behavioral changes that alter the feeding pattern of pigs, triggering a reduction in performance. In addition, the light program may also modulate the feeding behavior of pigs. Thus, data collected using electronic feeders were used to generate information on pig feeding behavior to identify anomalies that occurred due to variations in ambient temperature (cyclic heat stress) and after turning the lights on and off (light events). Our results indicated that cyclic heat stress disrupts the feeding circadian rhythm in finishing pigs. Pigs prioritized the feed intake in the coolest hours of the day. However, nocturnal cooling did not allow the pigs to fully compensate for the feed intake depression caused by heat stress. Furthermore, the lighting program affected the feeding pattern, increasing or decreasing the meal size when the lights were switched on or off, respectively. Understanding pig feeding behavior during cyclic heat stress and light events could improve feeding strategies, productivity, and animal well-being. ABSTRACT: The impact of cyclic heat stress (CHS) and turning the lights on and off on pig feeding behavior (FB) was investigated. The FB of 90 gilts was recorded in real-time under two ambient temperatures (AT): thermoneutrality (TN, 22 °C) or CHS (22/35 °C). The day was divided into four periods: PI ((06–08 h)); PII ((08–18 h)); PIII ((18–20 h)); and PIV ((20–06 h)). Automatic and Intelligent Precision Feeders recorded each feed event for each pig. An estimated meal criterion (49 min) was used to calculate the FB variables. Feed behavior in both ATs followed a circadian pattern. The CHS reduced the feed intake by 6.9%. The pigs prioritized feed intake during the coolest hours of the day; however, nocturnal cooling did not allow the pigs to compensate for the reduced meal size due to CHS. The highest meal size and most of the meals were observed during the lighting-on period. The pigs reduced their interval between meals during PII and PIII. The lighting program increased the meal size when the lights were switched on and reduced the meal size when the lights were switched off. Thus, the dynamics of the FB were largely influenced by AT, whereas the meal size was affected by the lighting program.