Energy requirements for maintenance and growth of wild mammals, birds and reptiles in captivity.

A wide range of wild animals are maintained in captivity as pets and an increasing number are likely to become dependent on captive breeding for conservation. Generally, these animals are fed ad libitum and a knowledge of their energy requirements is not essential. However, estimates of energy requirements are helpful in several situations: treating obesity, providing nutritional support to anorexic animals and feeding neonates. Data on basal metabolic rates (BMR) are available for approximately 5% of avian and 17% of mammalian species, and the maintenance requirement can be estimated at twice BMR. Estimates for other species can be based on allometric equations relating energy expenditure to body weight in the species that have been studied. Although between species time taken to grow increases with adult mass, wide variation remains after the effect of adult mass is considered. A model is developed which illustrates the impact of variation in time taken to grow on daily growth rate (per metabolic mass) at all stages of maturity. This model may assist in estimating the lower limit to energy requirements during growth.