Heat and moisture production of beef cattle based on acclimation period and modern genetics

Heat and moisture production can inform decisions for farm environmental controls and feed utilizations. Indirect calorimetry was applied to cattle using open-circuit chamber technology to explore. The main factors that might cause a bias to the results of heat and moisture production measurement is acclimation. Previous studies reported different acclimation periods varying from 2 to 17 days, demonstrating the need to document an approach for determining acclimation period for a system before implementing it in a study. Based upon behavior and metabolism indicators, a two-day acclimation period was adequate for mature steers in the research mature steers in the chamber on the Beef Cattle and Sheep Field Laboratory at University of Illinois, Urbana-Champaign. Current research showed the beef cattle had a bias in feed intake higher than CIGR models. The heat and moisture production models were published at 1980s using feed intakes in the equation. The measured heat and moisture production were also compared with CIGR models for heat and moisture production predictions to assess representativeness. The average total heat production of mature steers (1.38 W/kg) and sensible heat production (1.20 W/kg) for mature steers were higher than the prediction results from CIGR models. The steers used in the experiments were not at the same stages as animals in CIGR models and were likely genetically quite different (fattening and breeding bulls), but the results support the idea that the existing models are an insufficient representation of heat and moisture production for modern beef cattle.