Effects of Diet and Genetics on Production Traits in Response to Repeated Exposure to Heat Stress in Pigs

Abstract

Implications Hot temperatures negatively impact global livestock production and are a serious financial burden to pig producers. Trends predict that global temperatures will continue to increase, making this a pertinent issue now and in the future. Study objectives were to investigate the effects of genetics and dietary fiber content on growth, feed intake, and feed conversion efficiency in response to repeated exposure to heat stress. A total of 103 finishing barrows from a contemporary commercial line and Yorkshire lines divergently selected for high and low feed efficiency based on residual feed intake ( RFI ) were used in this experiment. All pigs were subjected three consecutive times to a 4-d heat stress ( HS ) load, starting with a 19-d thermal neutral ( TN ) adaptation period and alternated by 7-d TN conditions (see Figure 1). Feed intake, growth and feed conversion efficiency were measured for each period. Heat stress negatively impacted all three production traits, however, pigs from the commercial line were most affected. In addition, during heat stress, pigs from the low RFI (= more efficient) line lost their advantage in feed conversion efficiency over pigs from the high RFI line. This supports the hypothesis that pigs with a high genetic propensity for lean tissue accretion are more susceptible to heat stress. However, our results also indicated that the effect of heat stress on feed intake, growth rate, and feed conversion efficiency was not significantly influenced by the amount of fiber in the diet (at constant energy density).