Interpretive Summary: Elliptical and linear relationships with rumen temperature support a homeorhetic trajectory for DMI during recovery of feedlot cattle exposed to moderate heat load 

By: Megan. L. Sullivan , Gene Wijffels , A. George, Yousef A. Al-Hosni, Joseph C. W. Olm and John B. Gaughan

Over any summer, most feedlot steers in Australia will encounter 2 to 3 moderate heat waves lasting 5 to 6 d. The ability of these animals to adjust to the hot conditions and recovery from them is not well understood. The advent of obtaining near real-time body (rumen) temperature from feedlot steers has the potential to help feedlot managers, veterinarians and nutritionists make decisions on the handling of feedlots animals during and after heatwaves. Using climate-controlled rooms, this study demonstrated that feedlot steers are physiologically capable of dealing with moderate heatwave conditions. The coordinated increases in respiration rate, sweating rate, body surface temperature, and water consumption alongside reduction in feed intake as heat load increases limits the rise in body temperature. By the end of a 7-d recovery period in thermoneutral conditions, the heat stressed steers were not different physiologically and performance-wise from thermoneutral counterparts feeding on a similar amount of food. However, during the recovery period, all animals appeared to be metabolically and physiologically constrained, and did not return to their pre-heatwave feed intake, body temperature or respiration rate. These findings will assist the management of feedlot animals through recovery after a heat wave.

Read the full article on the Journal of Animal Science.