Effect of prepuberal and postpuberal gonadectpmy on heat production measured by indirect calorimetry in male and female domestic cats

Objective - To use indirect calorimetry to compare heat production between gonadectomized and sexually intact male and female cats. Design - Male (n = 6) and female (n = 6) kittens were gonadectomized at 7 weeks or 7 months of age, or left sexually intact. Body heat production was measured by indirect calorimetry in all cats at 12, 18, and 24 months of age. Animals - 18 male and 18 female clinically normal domestic shorthair cats. Procedure - Heat production was measured, using an open-circuit, respiratory, indirect calorimeter. All cats underwent calorimetry at 12, 18, and 24 months of age. The heat coefficient, a measure of resting metabolic rate, was calculated for each cat at each test, heat coefficient is defined as logarithm of heat (kcal/h) divided by logarithm of body weight (kg) Results - Heat production did not vary with age in male or female cats. Heat coefficient was higher in sexually intact male and female cats than in gonadectomized male and female cats at 12, 18, and 24 months of age (12 months, females, P < 0.01, males, P= 0 04, 18 months, females, P < 0 01, males, P = 0 02; and 24 months, females and males, P < 0.01). Conclusions - These data suggest that resting metabolic rate in cats decreases after gonadectomy. Clinical Relevance - A decrease in metabolic rate is synonymous with a decrease in caloric requirements. Gonadectomized animals fed in a manner similar to sexually intact animals may be predisposed to obesity and its sequelae.