Maintenance energy requirements of goats: predictions based on observations of heat and recovered energy

Abstract

A database including 80 treatment means, based on energy balance publications, was constructed and analyzed to estimate fasting heat production (FHP) and ME required for maintenance (ME_m) of goats. Experiments entailed comparative slaughter, respiration calorimetry or CO₂ entry rate techniques. Goats were of eight breeds and five physiological states (preweaning; growing; mature and non-lactating; early and mid-pregnancy; and lactating). Assuming that heat increment was 40% of total heat energy, unweighted, and weighted (number of observations per treatment mean) log–log regressions (n = 74 following removal of observations to increase explained variation) of FHP against BW resulted in FHP (kJ) = 299 × BW^0.762 (R² = 0.82) and 244 × BW^0.826 (R² = 0.75), respectively. The 0.762 and 0.826 BW scaling factors did not differ (P < 0.17) from 0.75. The slope and intercept of a regression of recovered energy (RE) against ME intake (MEI) for preweaning goats differed (P < 0.01) from those for other physiological states. A linear regression analysis of RE on MEI (both kJ/kg BW^0.75) was conducted with the remaining 71 observations, after removing two observations with SD greater than 2.5 residual SD. The resultant equation was: RE = −298.0 (SE = 22.38) + (0.691 (SE = 0.028) × MEI) [n = 69; R² = 0.90]. These estimates of FHP and efficiency of ME use yielded an estimate of ME_m of 431 kJ/kg BW^0.75. In summary, FHP and ME_m of 298 and 431 kJ/kg BW^0.75, respectively, appear appropriate as general descriptors of the maintenance energy requirement of goats consuming diets at, near or above maintenance.