Interpretive Summary: Evaluation of sow thermal preference across three stages of reproduction  

By: Dr. Emily Taylor

Heat stress has had significant adverse effects on the swine industry, including infertility in sows, characterized by anestrus, increased wean-to-estrus interval. However, heat stress is not limited to lactation. It may also affect a sow during gestation, causing increased embryo mortality, reduced farrowing rate, reduced litter size and weight, and an increased number of stillborn piglets. In addition, the metabolic heat production of modern pigs has increased by an average of 16%, and therefore, is temperature recommendations require updating to meet their needs. 

The objective of this study was to evaluate whether different reproductive stages of sows altered thermal preference and if current recommendations required updating. Sows in different reproductive stages (nonpregnant, mid-gestation, and late-gestation) could freely choose a temperature preference using a thermal gradient between 10.4 and 30.5 °C. Sow behavior, posture, and location were recorded over a 24-h test period. 

Results reported were that late-gestation sows preferred a cooler temperature (14 °C) than mid-gestation and nonpregnant sows (14.8 °C). The current temperature range recommendations are 10 to 25 °C, and it was found that modern sows preferred a temperature on the lower end of that range. Therefore, temperatures at the higher end of the recommended range could be uncomfortable for sows. The authors suggest that the thermal comfort zone of sows may need to be narrower than current recommendations indicate and that individual sows should be housed in temperatures between 12.6 and 16.4 °C to optimize production and improve the overall well-being.

This article is available on the Journal of Animal Science.