Age-related changes in gastrointestinal function have been reported in companion animals, but the impact on digestive efficiency remains uncertain. Healthy dogs (n = 37; 2.6–14.2 years) received four diets varying in total dietary fibre (TDF; 6–29%, as fed). Healthy cats (n = 28; 1–13 years) received four diets with two fat (10–12%; 17–18%) and TDF (9 and 12%) levels. In a crossover design, diets were provided over four consecutive 10-day cycles, including a 4-day faecal collection. Apparent crude protein (CP), ether extract (EE), TDF, calcium (Ca), and phosphorus (P) digestibilities were determined. The effect of age was analysed as a continuous variable in dogs and as differences between adult (1–5 years) and senior (7–13 years) cats. In dogs, EE digestibility was unaffected by age (p > 0.10). Dogs of 6–12 years had higher digestibility of CP (p = 0.032), TDF (p = 0.019), Ca (p = 0.019), and P (p = 0.024) when fed the 6% TDF diet. Senior cats had greater digestibility of TDF (p < 0.01) and Ca (p = 0.024) but had lower EE and CP digestibility with one diet (17% fat; 9%TDF) (age, p > 0.10; diet × age, p < 0.001). Healthy ageing was associated with preserved nutrient digestibility in dogs and cats within the age ranges studied. The effect of ingredient sources in senior cats warrants further investigation.

Domesticated cats have evolved from the obligate carnivore Felis silvestris. The instinct to eat small frequent meals and a crepuscular feeding rhythm was conserved during domestication. Declining senses, cognitive impairment, and poor oral health decrease food intake in aging cats. Combined with metabolic and physiological changes, they are at risk of sarcopenia and general body condition impairment. Aging cats may, therefore, benefit from modified nutritional strategies to achieve their metabolic energy requirements; however, little is known about feeding patterns in aging cats and influence of food format. This in-home study of 134 aging cats (≥7 years) assessed ad libitum dry, wet, and wet/dry (‘mixed’) feeding regimens to compare 24 h feeding frequency and caloric intakes. Feeding frequency was significantly different between wet and dry (p = 0.02) and mixed and dry diets (p < 0.001), with cats consuming 6.0 (dry), 6.9 (wet), or 7.2 meals (mixed) per day. Mean caloric intakes were significantly higher for dry (262.6 kcal/d) and mixed (222.6 kcal/d) regimens (both p < 0.001) versus wet (138.1 kcal/d). In conclusion, healthy aging cats eat small frequent meals, with feeding frequency and caloric intake influenced by dietary format. These findings support development of evidence-based feeding guidelines for aging cats.