EFFECT OF PREPUBERTAL AND POSTPUBERAL GONADECTOMY ON HEAT-PRODUCTION MEASURED BY INDIRECT CALORIMETRY IN MALE AND FEMALE DOMESTIC CATS

Objective-To use indirect calorimetry to compare heat production betwe en gonadectomized and sexually intact male and female cats. Design-Mal e (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 me asured by indirect calorimetry in all cats at 12, 18, and 24 months of age. Animals-18 male and 18 female clinically normal domestic shortha ir 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 rest ing metabolic rate, was calculated for each cat at each test; heat coe fficient 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 m ale 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, fema les 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 sexua lly intact animals may be predisposed to obesity and its sequelae.