Every animal must satisfy its requirements for the various types of nutrients through the assumption of these nutrients in the diet. Much information on nutritional requirements can be derived from the analysis of the food sources that each species would use in the wild. Various authors have examined the dietary habits of wild carnivores such as the wolf and coyote. Both are opportunistic predators and “scavengers”, hunters and consumers of locally available sources of food.1 Coyotes eat carrion and hunt rodents, other small mammals, birds, amphibians and other species.1,2 Ungulates such as buffalo, deer, elk, gnu, antelope, and zebra are the natural prey of wolves.1,2 The viscera of the prey are eaten, so the partially digested vegetal matter within them also form part of the diet of the wolf.3 Furthermore, both the coyote and the wolf eat vegetal substances such as fruit, berries, persimmon and mushrooms.1,2,4
Likewise, dogs are “opportunistic eaters” and have, therefore, developed a digestive anatomy and physiology that enables them to digest and use a wide variety of foods. The nutritional requirements of the dog and cat are numerous and a complete food ration should, therefore, supply:
- energy, in an amount equal to that released by the animal in the form of heat, retained by the animal itself in its tissues in the process of growth and that transferred in the production of milk or foetuses;
- proteins and essential amino acids, minerals, vitamins and essential fatty acids in sufficient amounts to meet the vital needs of the animal and those related to breeding.
The ration must also supply an adequate amount of fibre to ensure the correct function of the gastrointestinal tract and, overall, must have a bulk compatible with the size of the animal’s digestive system.
The amounts of the nutrients that must be supplied vary throughout the animal’s life and, obviously, also differ depending on the physiological state (even more so, if pathological conditions are present). Broadly speaking and as reported for humans, the correct amounts of the main nutrients can be represented by a pyramid (Fig.1) bearing in mind that the old principle stated by Paracelsus, “the dose makes the poison” holds true for dietary substances in that it is the amount of a food that determines whether the food is nutritional or harmful. The concept is well summarised in Fig. 2.
Fig. 1. The six basic nutrients. Fats, proteins and carbohydrates have both a structural function and the function of providing energy.5
Fig. 2. Effects of levels of intake of the main nutrients.
The physiological conditions for which nutritional requirements can be defined are:
- maintenance
- growth
- gestation and lactation
- work (only for dogs)
The nutritional requirements for dogs and cats are mainly defined by the American National Research Council (NRC) and the Association of American Feed Control Officials (AAFCO). Through experimental studies and reviews of the international literature, these bodies identify the minimal level, the recommended level and, if appropriate, the maximum level for each nutrient.
References
1. Sheldon JW. Genus Canis. In: Wild dogs: the natural history of the non domestic Canidae. San Diego, CA: Academic Press Inc, 1992; 23-61.
2. Landry SM, Van Kruiningen HJ. Food habits of feral carnivores: a review of stomach content analysis. Journal of the American Animal Hospital Association 1979; 15:775-782.
3. Beaver BV. Grass eating by carnivores. Veterinary Medicine/Small Animal Clinician 1981; 76:969-969.
4. Röhrs M. Die Domestikation von Wolf und Wildkatze Parallelen und Unterschiede. In: Meyer H, Kienzle E, eds. Ernährung, Fehlernährung und Diätetik bei Hund und Katze. Proceedings International Symposium, Hannover, Germany, September 3-4, 1987:5-12.
5.Gross KL, Yamka RM, Khoo C, Friesen KG, Jewell DE, Schoenherr WD, Debraekeleer J, Zicker SC. Macronutrients. In: Small Animal Clinical Nutrition 5th Ed. Topeka (KA): Mark Morris Institute, 2010; 49-105.