The Relationship between Heart Rate and Heat Production of Growing Pigs

Abstract

1. Heart rate (HR) and heat production (HP) of four castrated growing pigs, weighing from 35kg to 58kg, were measured simultaneously using a head cage. 2. There were apparent differences in both mean HR and mean HP for calibrations between individuals and between days. However, a close relationship between HR and HP was shown to exist in each calibration. 3. The prediction error (PE, sy•x/y, %), expressed as a percentage of mean level of y for the sample standard deviation from the regression, were within the range of ±5.7% to ±6.7% for the means of each animal. It is suggested that the HR measurements could offer a practical method of estimating HP of growing pigs. Differences in both regression coefficients and intercepts, at HR 130 (beats/min), were clearly found between days and between individuals. 4. The difference in the intercept between days could be modulated by use of relative heart rate (RHR). The RHR was a ratio of HR to basal HR, which is calculated by substituting the mean value of HP in all animals into the regression equation of each animal. However, the difference in the regression coefficients between individuals persisted. 5. For growing pigs, weighing about 35-60kg, the estimation of HP from a mean group HR with a minimum of 4 pigs was determined to eliminate the need for calibration for individual pigs, using the following equation. Y=-1.095+8.882X, Y=HP (Kcal/W0.75•h), X=RHR (RHR=HR/130.1) The mean value of basal HR was 130.1 (beats/min) for growing pigs weighing 35 to 58kg.