Feeding behavior of grow-finish swine and the impacts of heat stress.

Heat stress has negative impacts on pork production, particularly in the grow-finish phase. During heat stress events, the feeding behavior of pigs is altered to reduce heat production. Several different systems have been developed to study feeding behavior. Most systems are not accurate representations of grow-finish commercial production as feed intake is monitored for only one pig at a time. The objective of this study was to utilize a feed monitoring system, representative of commercial conditions, to determine feeding behavior patterns of grow-finish pigs throughout the year and to identify changes that occurred during heat stress events. Feeder visit data were collected on barrows and gilts (n = 932) from three different sire breeds, Landrace, Yorkshire, and Duroc, between May 2014 and April 2016. Days in the study were partitioned into groups based on their maximum temperature-humidity index (THI), where a THI less than 23.33 °C was classified as "Normal", a THI between 23.33 and 26.11 °C was classified as "Alert", a THI between 26.11 and 28.88 °C was classified as "Danger", and a THI greater than 28.88 °C was classified as "Emergency". Feeding behavioral differences among breeds and sex were observed across all THI categories. Landrace-sired pigs had fewer feeder visits compared to Duroc- and Yorkshire-sired pigs. Gilts had fewer feeder visits than barrows in all THI categories. Differences in feeding behavior patterns between THI categories demonstrated that heat stress reduced the feeding duration of Landrace-sired pigs without any dramatic effects on the other pigs in the study. During elevated temperatures, all pigs tended to increase feeding events during the early (03:00-05:59) and late (18:00-20:59) periods of the day. Utilizing a feed monitoring system that is a more accurate representation of commercial conditions will lead to a greater understanding of feeding behavior among breed types and sexes during heat stress, allowing producers to enhance their ability to properly care for their pigs during both normal and heat stress events.