The speed with which food transits through the gastrointestinal tract is a variable that can be influenced by factors that are intrinsic to the animal as well as by characteristics of the ration of food given. For this reason dietary strategies can be used to try to improve the symptoms of an animal with disordered gastrointestinal motility. Normally the stomach of a dog empties in 6 to 8 hours, whereas that of the cat takes 4 to 6 hours (Twedt, 2005).
The speed of gastric emptying is influenced by the formula, the nutrient content and the size of the meal and the body weight of the animal. (Nelson et al., 2001) The gastric emptying time is longer for large meals and dry food is propelled out of the stomach more slowly than wet food. (Goggin et al., 1998) Fluids, obviously, leave the stomach more quickly than solids, thanks to the lower osmolality of the former; this means that water is the fluid that transits through the stomach most quickly, while the gastric emptying times for fluids with a higher osmolality (because they contain nutrients) are longer. (Fleming, 1997) Furthermore, gastric emptying is optimised if the temperature of the food is between room temperature and body temperature. Finally, a recent study on long-term measurement of gastric motility, using passive telemetry, revealed significant differences in the patterns of post-prandial motility between Labradors and Beagles, although further studies on the effect of breed on gastric motility are required (Burger et al., 2006).
In the case in which problems of gastrointestinal motility are more cranial and, therefore, related to the oesophagus, even the position of the animal and its food and water can play a role; the passage of food into the stomach can be facilitated by placing food and water bowls in a raised place and/or keeping the animal in a vertical position after meals.(Guilfordand Matz, 2003).
The main nutrients to control in patients with disorders of gastrointestinal motility are discussed below.
WATER
The temperature of an animal’s drinking water should be between room temperature and body temperature, because cold water slows gastric emptying. In the case of constipation, particularly in cats, it can be useful to administer food with a humidity of ≥ 75% in order to ensure optimal assumption of water with the food.
ENERGY
From a practical point of view, it is advisable to use food rations 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.
FATS
Excessively high levels of lipids cause an increased production of cholecystokinin in the duodenum, which slows gastric opening. On the other hand, a certain amount of lipids in the daily ration enables smaller quantities of food to be administered and renders the food more palatable (which can be important if there are symptoms of nausea). For these reasons the recommended levels of lipids are between 12 and 15% (of the dry weight of the substance) in the dog and between 15 and 25% (of dry weight) in the cat.
FIBER
The term “fiber” refers to numerous compounds classed as complex carbohydrates. Since this category includes compounds with profoundly different characteristics, it can be confidently stated that this food constituent is the alimentary factor of greatest importance in the regulation of gastrointestinal motility. The different types of fiber are still classified according to their speed of fermentation and their solubility in water. Generally speaking it can be said that the more readily fermentable fibers produce greater amounts of short chain fatty acids and gas. Furthermore, such fibers are more soluble and have a greater capacity to bind to water. Dietary fiber has particular functions in dogs and cats, because it promotes correct intestinal function by normalising gastrointestinal motility (Burrows et al., 1982) and is a substrate for the microbial-mediated production of the short chain fatty acids which nourish colonic cells. Many wet foods contain gelifying agents such as gums or hydrocolloids (in order to improve the appearance of the food).
Soluble fibers that give rise to a gel should be avoided in subjects affected by delayed gastric emptying because they can increase the viscosity of the gastric contents, further delaying emptying of the stomach (Russell and Bass, 1985; Burger et al, 2006). In contrast, increased levels of insoluble fibers (e.g. bran, cellulose) do not have any effect on gastric emptying in the cat (Armbrust et al., 2003). Some authors believe that the ratio between rapidly and slowly fermentable fibers is important (Kritchevsky, 2001).The recommended level of fiber (expressed as crude fiber) in cases of patients with delayed gastric emptying is below 5% (of dry weight). On the other hand, soluble fibers that give rise to the formation of a viscous, gelatinous mass (e.g. psyllium, guar gum, pectin) can be exploited, with excellent results, in all those disturbances of hypermotility in which it is necessary to slow the transit and bind excess water or in cases of constipation, which benefit from an increase in the water content of the faeces. Both soluble and insoluble fibers are essential in the management of constipation. The recommended amount of fiber for patients predisposed to constipation must be at least 7% (expressed as % of crude fiber of dry weight).
VITAMINS AND MINERALS
When fluids are lost through the gastrointestinal tract, it is important to control the supply of potassium, chloride and sodium. In the case of chronic pathologies, the continuous loss of water through the gastrointestinal tract causes the loss of water-soluble vitamins, in particular (group B vitamins).
Proteins do not have a specific role in regulating motility, whereas there are descriptions of the use of some carbohydrates (e.g. lactose) in the management of constipation because of the capacity of these compounds to draw water into the intestinal lumen.
In summary, there is growing interest in the regulation of gastrointestinal motility through nutritional strategies, although this requires further study considering that biological, chemical and physical variables are involved.
Suggested readings
- Armbrust LJ, Hoskinson JJ, Lora-Michiels M, et al. Gastric emptying in cats using foods varying in fiber content and kibble shapes. Vet Radiol Ultrasound 2003; 44: 339-43.
- Burger DM, Wiestner T, Montavon PM, et al. Long-term measurement of gastric motility using passive telemetry and effect of guar and cellulose as food additives in dogs. J Vet Med A Physiol Pathol Clin Med 2006;53:85-96.
- Burrows CF, Kronfeld DS, Banta CA, et al. Effects of fiber on digestibility and transit time in dogs. J Nutr 1982;112:1726-32.
- Fleming CR. Physiology of the gastrointestinal tract: as applied to patients receiving tube enteral nutrition. In: Rombeau JL, Rolandelli RH, et al, eds. Clinical Nutrition; Enteral and Tube Feeding. Philadelphia. PA: WB Saunders Co, 1997;12-22.
- Goggin JM, Hoskinson JJ, Butine MD, et al. Scintigraphic assessment of gastric emptying of canned and dry diets in healthy cats. Am J Vet Res 1998;59:388-92.
- GuilfordWG, Matz ME. The nutritional management of gastrointestinal tract disorders in companion animals. NZ Vet J 2003; 51: 284-91.
- Kritchevsky D. Dietary fiber in health and disease. In: Advanced Dietary Fibre Technology. Oxford, UK: Blackwell Science Ltd, 2001;151.
- Nelson OL, Jergens AE, Miles KG, et al. Gastric emptying as assessed by barium-impregnated polyethylene spheres in healthy dogs consuming a commercial kibble ration. J Am Anim Hosp Ass 2001;37:444-52.
- Russell J, Bass P. Canine gastric emptying of fiber meals: influence of meal viscosity and antroduodenal motility. Am J Physiol 1985; 249: G662-G667.
- TwedtDC. Gastric or gastrointestinal motility disorders. In: Tilley LP, Smith FWK, eds. The 5-Minute Veterinary Consult. 3rd edition. Baltimore, MD: Lippincott Williams & Wilkins, 2004:494-5.