Estimation of heat production from heart-rate measurements in cattle.

1. Heat production and heart rate of seven steers were measured simultaneously using either a calorimetric chamber or head-cage. 2. The relationship between heat production and heart rate for each animal was best described by linear regression. 3. Differences between individual animals made separate 'calibration equations' necessary for each animal. 4. Accuracy of prediction of heat production from heart rate was better than +/- 10% in all instances. 5. It is concluded that frequent measurement of heart rate appears to offer a practical method for estimation of heat production of free-range animals.