Effect of sterilization and of dietary fat and carbohydrate content on food intake, activity level, and blood satiety-related hormones in female dogs.

Animal sterilization is suggested to promote food overconsumption, although it is unknown whether this effect is mediated by variations in satiety-related hormones, which are released in response to food intake. The aim of this study was to evaluate the effect of sterilization and of the main energy-delivery nutrients, fat and nonstructural carbohydrates, on food intake, blood concentration of satiety-related hormones, and activity level in dogs. In a 2-phase experiment (phase I [Ph.I], 74 d, and Ph.II, 84 d), 12 female Beagle dogs were assigned to a control group (intact in both phases) and a sterilization group (spayed 20 d before Ph.II). In each phase, dogs received a high-carbohydrate (HC) diet (313 and 105 g/kg DM starch and fat, respectively) and a high-fat (HF) diet (191 and 213 g/kg DM starch and fat, respectively), both high in total dietary fiber (>200 g/kg DM) and providing 27% ME as protein, in 2 consecutive periods following a crossover arrangement. During each period, dogs' voluntary DMI and activity level were recorded during 5 d. Then, energy allowance was restricted to 0.7 maintenance and the level of intake of a common challenge food offered 4 h after feeding the experimental diets (challenge food intake [ChFI]) was used as an index of the satiety state of dogs. Blood concentration of active ghrelin, cholecystokinin (CCK), total peptide YY (PYY), and insulin were determined before and 15, 60, 120, 240, and 360 min after feeding. Voluntary DMI was greater ( < 0.05) in HF-fed dogs, but ChFI did not differ between diets ( > 0.10). Dogs fed the HF diet showed a lower increase of CCK at 120 ( < 0.01) and 240 min ( < 0.05), resulting in a lower ( < 0.001) total area under the curve from 0 to 240 min (tAUC). A lower PYY elevation ( < 0.05) was also found in HF-fed dogs at 120 min. Only active ghrelin concentration at 240 min and insulin tAUC correlated ( < 0.05) with ChFI (r = 0.357 and r = -0.364, respectively), suggesting a role of these hormones in appetite. Dog sterilization did not affect voluntary DMI, ChFI, or blood hormones ( > 0.10) but led to a reduced activity level compared with control dogs ( < 0.05). In summary, dog sterilization was not associated with an impaired appetite control. Feeding dogs the HF diet led to energy overconsumption and to a lower blood elevation of CCK and PYY but was not associated with a weaker satiating effect 4 h later compared with the HC diet.