Geometric analysis of macronutrient selection in breeds of the domestic dog, Canis lupus familiaris.

Although many herbivores and omnivores have been shown to balance their intake of macronutrients when faced with nutritionally variable foods, study of this ability has been relatively neglected in carnivores, largely on the assumption that prey are less variable in nutrient composition than the foods of herbivores and omnivores and such mechanisms therefore unnecessary. We performed diet selection studies in 5 breeds of adult dog (Canis lupus familiaris) to determine whether these domesticated carnivores regulate macronutrient intake. Using nutritional geometry, we show that the macronutrient content of the diet was regulated to a protein:fat:carbohydrate ratio of approximately 30%:63%:7% by energy, a value that was remarkably similar across breeds.

Consistent proportional macronutrient intake selected by adult domestic cats (Felis catus) despite variations in macronutrient and moisture content of foods offered.

We investigated the ability of domestic cats to regulate the macronutrient composition of their diet when provided with foods that differed not only in macronutrient content but also in texture and moisture content, as typically found in the main forms of commercially manufactured cat foods. Cats were provided with foods in different combinations (1 wet + 3 dry; 1 dry + 3 wet; 3 wet + 3 dry) in three separate experiments. Within each experiment cats were offered the wet and dry food combinations in two (naïve and experienced) diet selection phases where all the foods were offered simultaneously, separated by a phase in which the foods were offered sequentially in 3-day cycles in pairs (1 wet with 1 dry).

Geometric analysis of macronutrient selection in the adult domestic cat, Felis catus.

We report feeding studies on adult domestic cats designed to disentangle the complex interactions among dietary protein, fat and carbohydrate in the control of intake. Using geometric techniques that combine mixture triangles and intake plots from the geometric framework, we: (1) demonstrate that cats balance their macronutrient intake, (2) estimate the composition of the target balance and (3) reveal the priorities given to different macronutrients under dietary conditions where the target is unachievable. Our analysis indicates that cats have a ceiling for carbohydrate intake, which limits ingestion and constrains them to deficits in protein and fat intake (relative to their target) on high-carbohydrate foods.