The significance of carbon dioxide and methane measurements in the estimation of heat production in cattle

1. Records of metabolic measurements on cattle by open-circuit indirect calorimetry have been examined to determine the practical significance in the calculation of heat production of including measurements of carbon dioxide and methane in addition to the measurement of oxygen. 2. It was found that the combined effects of CO2 and CH4 made only a small contribution to the total estimation of heat production which could be calculated with approximately +/- 1% accuracy from analysis of O2 alone.