Nutritional requirements of the dog and cat: maintenance

An animal is in a maintenance state when its weight and body composition are not changing, when it is not carrying out any work and when it is not pregnant or lactating. For this reason it is by far and away the most common condition in domestic pets.

The energy requirements in this condition are:

• the energy required for the physiological functions essential for life (corresponding to the basal metabolism);
• the energy expended for digestive processes;
• the energy required for the animal’s spontaneous activity (maintenance of posture, spontaneous movements, walking).

The maintenance energy requirement is considerably higher than the basal metabolism (determined in fasted animals at rest in an environment with a temperature within the zone of thermal neutrality. According to studies by Brody, the energy demand in maintenance conditions, expressed as metabolisable energy (ME), is about double the basal metabolism._¹ Consequently the energy requirement is not directly proportional the animal’s body weight, but to its metabolic weight. The metabolic weight depends on the surface area of the animal’s body and is usually calculated by raising the body weight by the power of 0.75.

Maintenance requirements are influenced by many intrinsic and extrinsic factors. With regards to the intrinsic factors, the maintenance requirements depend on the age of the animal, its gender (being lower in sterilised subjects) and its character (this being a fundamental factor when determining the spontaneous movements performed). Furthermore, there are differences between breeds, since there are some breeds with lower requirements (for example, Retrievers)_² and other with higher requirements (for example, the Great Dane)._³ Of the extrinsic factors, the environmental conditions in which the dog is kept are particularly important. There is a marked increase in heat production or heat dispersion at temperatures below or above the zone of thermal neutrality and, therefore, an increase in maintenance energy requirements.

Some of the above mentioned factors are readily determined (such as age and, obviously, gender) and can, therefore be easily considered in the calculation of energy requirements; others, such as the quantification of spontaneous movement, are characterized by a fairly high margin of uncertainty. For these reasons there is individual variation in the maintenance energy requirement; in principle, however, the maintenance energy requirement can be calculated based on the indications presented in Tables 1 and 2.

Table 1. Daily maintenance energy requirements of the dog_⁸. Resting energy requirement (RER) = 70 x body weight_^0.75

Table 2. Daily maintenance energy requirements of the cat._⁸ Resting energy requirement (RER) = 70 x body weight_^0.75

The maintenance protein requirements depend on the expenditure of nitrogen-containing matter by the body. The body’s proteins are continuously broken down and re-synthesised. The amino acids released in this process form, together with those of dietary origin, a pool for the synthesis of new proteins that replace those degraded. The biological value of the protein influences the maintenance protein requirement, which will be all the higher when the biological value of the proteins delivered in the diet is lower. For this reason the protein requirement of the dog is expressed generally but should also, more correctly, be expressed as the requirement for essential amino acids.

The maintenance requirements for minerals and vitamins are relatively modest. An animal is, in fact, able to exploit mechanisms to spare these and minimise their losses. However, since some losses cannot be prevented, a supply of mineral elements is necessary. The maintenance vitamin requirements are mainly influenced by the involvement of the vitamins in enzymatic functions in metabolic processes._¹

Lipids constitute an efficient source of energy but it is not this function that makes them indispensible nutrients for dogs and cats since maintenance energy requirements could, theoretically, be satisfied by proteins and carbohydrates. What does make lipids an indispensible part of the diet of dogs and cats is their supply of essential fatty acids (EFA) and their function of enabling absorption of fat-soluble nutrients (for examples, vitamins). The requirements for lipids in general and EFA in particular are reported in the tables below.

Water, although not always considered, is essential for life and is, in absolute, the most important nutrient and the major constituent of the body given that:

• it is the solvent in which many chemical compounds are dissolved and transported through the body;
• it is indispensable in chemical reactions of hydrolysis which occur in the metabolism of other nutrients;
• it plays a role in the regulation of body temperature and homeostasis;
• it determines the maintenance of the shape and structure of the animal.

Water is lost in maintenance conditions through urination, defecation, evaporation and respiration; these losses can be balanced by water derived from the metabolism of nutrients and by exogenous water (that is, derived from food and/or drinks). As a general rule it can be said that the water requirements of dogs and cats, expressed in ml/die, correspond to the energy requirements (in kcal/die)._⁴

Carbohydratesare widely used in food products for companion animals for reasons related to the production technology of the foodstuffs and because it an important source of energy. Nevertheless, there are no real, specific requirements for carbohydrates because the glucose that these supply can be obtained from glucogenic amino acids or the glycerol derived from fats.

From among the carbohydrates, fibre deserves a separate discussion. The term fibre refers to the numerous compounds classified as complex carbohydrates. Fibre differs from starches because it is resistant to the enzymatic digestion that takes place in the small bowel and is fermented in the colon by a variety of microbes. For this reason the different classes of fibre sources are still classified according to the speed of their fermentation and their solubility in water. Generally speaking it can be said that the more fermentable sources of fibre produce larger amounts of short chain fatty acids (SCFA) and more gas. Furthermore, these sources of fibre are more soluble and have a greater capacity to bind water. Fibre in the diet of dogs and cats has particular functions because it determines the correct function of the bowel by normalising intestinal motility_⁵ and is the substrate for the microbial production of the SCFA that provide nutrition for colon cells. Furthermore, it has been shown in many species that fibre has a role in preventing pathologies such as obesity, diabetes mellitus and disorders caused by gastrointestinal tract bacteria._^6,7

Various bodies (the American National Research Council, Association of American Feed Control Officials [AAFCO], etc.) have established nutrient requirements and for this reason there can be differences depending on the source cited. Table 3 and Table 5 report the maintenance levels of nutrients for dogs and cats established by the AAFCO._⁹ Table 4  and Table 6 present the maximum levels of those nutrients for which a toxic level is known.

References

1. Ladetto G. Dispense di Nutrizione ed Alimentazione Animale. CUSL Facoltà di Medicina Veterinaria di Torino (2002).
2. Diez M., Nguyen P.. Obesità: epidemiologia, fisiopatologia e trattamento del cane obeso. In: Pibot P., Biourge V., Elliott D. - Enciclopedia della Nutrizione Clinica del cane. – Aniwa sas Ed. (2007).
3. Männer K. Energy requirement for maintenance of adult dogs of different breeds. In: Abstract book. Waltham International Symposium on the Nutrition of Small Companion Animals, University of California, Davis, September 4-8, (1990):14.
4. Haskins SC. Fluid and electrolyte therapy. Compendium on Continuing Education for the Practicing Veterinarian 1984; 6: 244-257.
5. Burrows CF, Kronfeld DS, Banta CA, et al. Effects of fiber on digestibility and transit time in dogs. Journal of Nutrition 1982; 112: 1726-1732.
6. Benno Y, Nakao H, Uchida K, et al. Impact of the advances in age on the gastrointestinal microflora of beagle dogs. Journal of Veterinary Medical Science 1992; 54(4): 703-706.
7. Terada A, Hara H, Oishi T, et al. Effect of dietary lactusucrose on fecal flora and fecal putrefactive factors of cats. Microbial Ecology in Health and Disease 1993; 5: 87-92.
8. Gross KL, Yamka RM, Khoo C, Friesen KG, Jewell DE, Schoenherr WD, Debraekeleer J, Zicker SC. Macronutrients. In: Small Animal Clinical Nutrition 5^th Ed. Topeka (KA): Mark Morris Institute, 2010; 49-105.
9. Association of American Feed Control Officials. Official Publication, 1999; 122-144