Nutrition of dogs and cats with gastrointestinal disorders

Nutritional management of patients with gastrointestinal disorders is one of the situations that the pratictioner encounters most frequently in daily clinical practice. The animal’s diet sometimes has a direct role in the aetiology of gastrointestinal disorders but, even in the cases in which itNutrition of dogs and cats with gastrointestinal disorders is not involved in the aetiology, it is nevertheless a factor that influences, positively or negatively, the therapeutic outcome. From a practical point of view, in order to plan a diet correctly, it is essential to know the maintenance requirements of the animal, how these requirements change in relation to the type of gastrointestinal disorder and/or symptoms and which foods and how much of them are necessary to meet these requirements.

From the nutritional point of view it is obviously essential to distinguish between “food-responsive” and “food non-responsive” pathological states, although what interests the nutritionist more, because it has a direct influence on the dietary management, is the part of the gastrointestinal tract affected given that this becomes less efficient at transforming the main nutrients or more sensitive to them.

Furthermore, the maintenance energy requirements of a patient affected by a gastrointestinal tract disorder are increased because digestion is an energy intensive process: indeed, a common error is to undervalue the affected animal’s energy needs. From a practical point of view, it is advisable to give a ration with a high energy density (>400 kcal/100 g of food) in order to supply all the energy that the animal needs in a relatively small volume of food.

WATER

Water is the single most important nutrient and is the major constituent of animals. Water losses in maintenance conditions are due to urination, defecation, evaporation and respiration and can be balanced by water derived from the metabolism of nutrients and by exogenous water (that is, water assumed with foodstuffs and/or drinks). As a general rule, the water needs of cats and dogs, expressed in ml/die, are equivalent to the energy requirements expressed in kcal/die (Haskins, 1984); thus, in patients with gastrointestinal disorders, the water needs are increased. The temperature at which the water is administered is important in the case of disorders of gastrointestinal motility.

PROTEINS

The maintenance requirements of proteins depend on the expenditure of nitrogenous substances by the body. Body proteins are subject to continuous degradation and reconstruction. The amino acids released during degradation form, together with the amino acids originating from food, a pool used for the synthesis of new proteins which replace those broken down. For this reason, although protein needs in cats and dogs are usually expressed in general, they should, more correctly, be expressed as the needs of essential amino acids. In the case of patients with a gastrointestinal disorder, the recommended amount of protein depends on the site and the aetiology of the disorder. Furthermore, if the pathological state is “food-responsive”, the requirements must obviously be satisfied while limiting the protein sources to the minimum possible (of which, usually, only one of animal origin) or using hydrolysed proteins.

In pathological conditions such as gastritis (Fig.1) and enteritis it is important to limit the protein supply because the breakdown products of proteins (peptides, amino acids and amines) cause an increase in the production of gastrin and acid secretions (Feldman et al., 1980; Delvalle et al., 1990). In the case of protein-losing enteropathies, however, the “loss” of proteins should be considered in the overall calculation of protein needs. Supplies of specific amino acids, such as glutamine (at a dose of 0.5 g/kg of body weight), which are trophic factors for enterocytes, improve mucosal integrity (Windmueller et al., 1978). Protein levels do not seem to have an effect in the case of colitis (Fig. 2), while an improvement of the biological value and digestibility of dietary proteins could be useful in patients with flatulence (Suarez et al., 1999).

LIPIDS

The lipid content in the diet of an animal with gastrointestinal disease is very important because fats confer a ration a higher energy density (kcal/100 g) and, therefore, the possibility of satisfying energy needs through the administration of smaller volumes of food. A second advantage of administering adequate amounts of lipids is that of increasing the palatability of the food (which can be useful in cases of nausea or loss of appetite). However, high levels of fats are contraindicated in animals with disorders of gastrointestinal motility such as delayed gastric emptying. Some authors have described a decrease in the risk of gastric dilatation volvulus when food particles of a diameter of greater than 30 mm are associated with a limited amount of lipids (Theyse et al., 1998). Hypothetically, the administration of n-3 fatty acids (e.g. EPA, DHA) could have a positive effect on mucosal inflammation at any level, but there are specific data from pets only in the case of chronic colitis (Simopoulos, 2002; Barbosa et al., 2003).

VITAMINS AND MINERALS

In the case of chronic pathological conditions, the continued loss of water through the gastro-intestinal tract causes loss of water-soluble vitamins (group B vitamins) in particular. This deficiency can be manifested by loss of appetite and changes in the levels of serum amino acids (Ruaux et al., 2001; Ruaux et al., 2005). The vitamins affected most are thiamin, cobalamin and folates. A controlled study showed that cobalamin supplementation in cats with small bowel disease improved body weight and the signs of vomiting and diarrhoea (Ruaux et al., 2005). The absorption of lipid-soluble vitamins is compromised only in the case of steatorrhoea.

FIBER

This term refers to a huge number of compounds categorised as complex carbohydrates. Fiber differs from starches because it is resistant to the enzymatic digestion that occurs in the small bowel and is fermented in the colon by microbes. For this reason, the different fiber sources are still classified according to their speed of fermentation and solubility in water. Generally speaking, the types of fiber that are most readily fermented produce greater amounts of short chain fatty acids and more gas. Furthermore, these types of fiber are more soluble and have a greater capacity to bind water. The inclusion of fiber in the diet of dogs and cats is of particular importance because it can correct intestinal function and represents the substrate for the microbial production of the short chain fatty acids that nourish colonic cells. Furthermore, in many species, it has been demonstrated that fiber has a role in preventing diseases such as obesity, diabetes mellitus  and pathologies of bacterial origin of the intestinal tract (Benno et al., 1992; Terada et al., 1993). The benefits of fiber in the diet are enhanced in the management of colitis, in which it is useful to increase the levels of both soluble and insoluble fibers. In the case of disorders of gastrointestinal motility it is the type of fiber that plays a fundamental role in accelerating or slowing the gastrointestinal transit times.

DIGESTIBILITY

The digestibility of the ration destined for a patient with a gastrointestinal disorder deserves a separate discussion. Simplifying, a patient with compromised digestion requires a diet that supplies all the main nutrients that the animal needs while causing the minimum stress to its digestive system. For this reason, all the foodstuffs supplied must be exploited to the best. This concept is summarised in the term “digestibility”. Although this term does not have a specific normative reference, a food is usually defined as “highly digestible” when the digestibility of proteins is ≥87% and that of fats is >90%. The digestibility of a food depends on various factors including the sources of the main nutrients, the heat treatment to which the food is subjected, and the contemporaneous presence of primary ingredients that depress digestibility (e.g. cellulose). Most foods available on the market for “maintenance” alimentation have a digestibility between 69 and 78% as far as regards proteins and between 79 and 85% for fats (Kendall et al., 1982). The digestibility of commercial foods planned for animals with gastrointestinal problems is higher as a result of the choice of primary ingredients and the treatments to which they are subjected (Gross et al., 2010).

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