Effect of ovariohysterectomy on maintenance energy requirement in cats.

OBJECTIVE: To determine whether maintenance energy requirement (MER) to maintain stable body weight (BW) is substantially lower for spayed female cats than for sexually intact female cats and to assess whether an equation commonly used to estimate MER would accurately predict caloric need in spayed cats.
DESIGN: Prospective study. ANIMALS: 10 spayed and 5 sham-operated young adult female cats. PROCEDURE: During an acclimatization period, initial daily food allowance was determined by estimating MER as 1.4 x (30 x BW + 70), then adjusted weekly to maintain BW within 200 g of baseline. Ovariohysterectomy (OHE) or sham laparotomy was performed at week 7, and the study was continued for 15 additional weeks (period 1). To correct for a presumptive effect of continued musculoskeletal growth that resulted in some cats becoming unacceptably thin during period 1, the study was repeated over an additional 10 weeks (period 2), using a new estimate of MER calculated from BW measured after reestablishing normal body condition.
RESULTS: Substantial restriction in food allowance was necessary to prevent BW gain in the OHE group during both periods. Caloric intake of spayed cats in dietary balance was significantly lower than that of control cats at the end of each study period. Sexually intact cats appeared to self-regulate food intake, whereas spayed cats tended to eat all food available to them. Significant differences were not detected between OHE and control groups in observations of physical activity before or after surgery. The equation used to predict caloric needs overestimated the apparent MER for spayed and sexually intact cats. CLINICAL IMPLICATIONS: Ad libitum feeding of spayed cats may be inadvisable, and careful monitoring of food allowance, relative to body condition, is suggested to prevent excessive weight gain.