Effect Of Age On Energy Expenditure Assessed By Doubly Labelled Water In 1 To 16-Year Old Cats

Maintenance energy expenditure (EE) and requirements of the cat refer mainly to body weight, sexual status and activity. A recent study did not show any effect of age or season on EE when expressed as a proportion of lean mass. The aim of this study was to assess the effect of age on EE assessed using doubly labeled water (DLW) in cats in a wider range of age, from 1.2 to 16.6 y. EE was determined in young (18 y; 7 females, 11 males, neutered) free-living cats. The space available in the indoor facilities allowed similar social activity. Animals were fed with dry foods (similar food quotient). Cats received DLW intravenously (0.170 g/kg BW of both 2H2O and H218O). Blood samples were collected over a 12-d period. The free-fat mass (FFM) was assessed from body water pool (18O dilution), VCO2 from elimination rates of 18O and 2H, and EE from VCO2 and Weir formula. EE varied among the age groups (but not between genders) when corrected for BW, BW0.75, FFM or FFM0.75. (EE= 80 – 1.4.Age kcal/kg FFM, R2=0.4, p<0.01). The lower EE in aged cats was especially confirmed in 12 animals which EE was assessed twice, when they were 1.2 y then 12.7 y old (78 ± 2 vs. 66 ± 3 kcal/kgBW0.75; 102 ± 2 vs. 85 ± 3 kcal/kgFFM0.75). These results confirm that energy expenditure corrected for BW or FFM is lower in aged compared to young adult cats (approximately 15% less from 1.2 to 12.7 y).