Pet Nutrition: Requirements and related diseases Part 6 Nutrition in Disease Management

While American Feed Control Officials (AAFCO) and the National Research Council (NRC) cooperate to publish dog and cat nutrient profiles for growth, maintenance, and reproduction, this series goes beyond the percentages suggested by these organizations and explores in more detail why nutrients are required and what happens if they are not supplied in sufficient quantities. In part 1 we discussed water and energy, in part 2 we talked about protein, fats, carbohydrates and fiber and in part 3 we looked at vitamins and minerals. Part 4 discussed pet food types and labels, in part 5 we learned what should be considered while feeding our pets throughout their various life stages. Our conclusion today discusses the important role of nutrition in disease management. In detail we are going to briefly address some of the more commonly seen problems like adverse reactions to food, anemia, anorexia, cachexia, diarrhea, congestive heart failure (CHF), constipation, diabetis mellitus, feline lower urinary tract disease (FLUTD) fever, gastric dilatation or bloat, head trauma, burns and respiratory diseases, hepatic disease, hyperlipidemia in canines, malabsorption and maldigestion in dogs, obesity, pancreatitis and parvovirus enteritis in dogs, renal insufficiency, urolthiasis in dogs and steatitis in cats.
Nutrition is an important part of disease management, even though few disorders can be cured solely with diet. The interaction between illness, health, and nutritional status is multi factorial and complex. The nutritional requirements of sick dogs and cats are qualitatively the same as those of healthy ones; however, they differ in the amounts required, certain nutrients may be needed in greater amounts or may need to be restricted.

Adverse Reaction to Foods
Food reactions are classified using specific terminology. An adverse reaction to a food is a clinically abnormal response to any type of food ingested. Food intolerance is a type of adverse reaction that does not involve the immune system, eg, food poisoning. A food allergy is a type of adverse reaction that does involve the immune system, eg, colitis or atopy.

Dogs and cats with food allergy usually have GI signs (eg, vomiting or diarrhea, or both) or a pruritic skin condition. The prevalence of true food allergies is very small. Most dogs and cats with nonseasonal pruritus are having an adverse reaction to food. Unfortunately, food allergy cannot be differentiated from intolerance. Hence, given all the possible etiologies and limited diagnostics available, any animal suspected of having an adverse reaction to food should be fed a single novel protein, single novel carbohydrate diet with little or no known additives for a 2-mo trial period. If the owner elects to feed a commercially prepared food, several products are available that use single novel protein sources (eg, venison, rabbit, duck, or fish) and a single carbohydrate source (eg, potato). Fish is not a novel option for most cats. A careful dietary history must be obtained from the pet owner prior to selecting the type of diet. There is a possible, but yet unclear, relationship between adverse food reactions in cats fed foods containing scombroid fish and histamine content. Most importantly, the formulation of whatever product or diet is fed must be fixed to ensure that the ingredient composition is consistent from batch to batch. These products are more expensive not only because of their unique and limited sources of protein but also because of the quality control procedures required to ensure fixed formulations and to eliminate cross-contamination with previous production batches of different foods.

Simplified homemade diets are also possible using the same protein and carbohydrate sources suggested above (or other ingredient sources the owner wants to test). Homemade diets actually allow for a wider selection of source ingredients. Beef, lamb, pork, mutton, tofu (soybean), egg, and dairy products should be discouraged as protein sources because animals have likely been exposed to these sources if previously fed foods with an open formulation. Likewise, corn, wheat, barley, and rice should be discouraged as carbohydrate sources. The basic recipe should closely resemble “complete and balanced,” but single sources of protein and carbohydrate can be sequentially tested and replaced. The owner is responsible for quality control and consistency and must be willing to make such a diet for ~2 mo. On average, there is no price advantage in making a homemade diet over using commercially prepared foods.

The trial diet should be exclusively fed for the 2-mo period, eliminating all treats, snacks, and table foods unless made of the exact same ingredients as the trial diet. All chewable medications and supplements must be eliminated from the trial diet because most contain the same protein and additive ingredients as pet foods and treats. A positive diagnosis of adverse reaction to food is made when there is ~50% improvement within 3 mo of eating the trial diet. Other therapies such as hyposensitization and flea control are necessary in animals with concurrent disease. Testing various suspect ingredients by reintroducing them to the diet one at a time followed by recurrence of clinical signs is affirmation of an adverse reaction to that ingredient. Dietary ingredients reintroduced could reproduce clinical signs as early as 12 hr after ingestion but could take as long as 10 days. Lifelong treatment is dietary avoidance, which may be difficult if the offending ingredients are not positively identified.

Anemia:
Iron or copper deficiency (or both) is the major cause of hypochromic, microcytic anemia. A folic acid and B12 deficiency also produces anemia. Most commercial diets have more than required amounts of iron, copper, and vitamins; therefore, secondary causes such as hemorrhage or heavy parasite infection should be investigated. Feeding large proportions of a single item food or an unbalanced homemade diet may result in anemia. The objective of dietary management of anemia is to feed a diet that is known to support RBC production; this avoids the possibility of a particular nutrient acting as the limiting factor. Ample amino acids must be available for the synthesis of Hgb, iron for heme synthesis, and copper for the proper mobilization of iron. Folic acid and vitamin B12 are necessary to support normal cell division, although there is probably a 2-5 yr hepatic supply of B12 in previously normal animals. Anemic dogs or cats should be fed a growth diet to provide adequate nutrition rather than individual synthetic nutritional supplements. Adding cooked liver to the existing diet is another major source of these nutrients but should not be included at >10-15% of the total food fed.

Anorexia:
Anorexia (partial or complete) accompanies many disorders, including drug reactions or reactions to environmental changes. Learned food aversions may also contribute to anorexia. Pain may also be a significant contributor to anorexia, and in most cases when the pain is adequately controlled, the anorexia resolves. The nutritional goal is to stimulate normal appetite and maintain adequate food intake. Partial anorexia is seen when the animal is eating some food but not enough to provide at least 30 kcal/kg body wt in dogs and 40 kcal/kg body wt in cats. Complete anorexia is when the animal eats nothing for ~3 days. Anorectic dogs and cats can sometimes be persuaded to eat by adding highly flavored substances to the diet (eg, animal fat, meat drippings, fish [fish juices or oils for cats]). Nutrition can be provided by several methods for anorectic dogs and cats that are hospitalized. Tube feeding using either a nasogastric or gastric tube is most common. Nasogastric tubes are used more commonly for short durations (1-7 days), while gastric tubes are more convenient for longer durations (weeks or months). Dogs and cats can be maintained at home with tube feedings after the procedure has been accepted by the animal and fully explained to the owner. The liquid tube feeding diet should be nutritionally dense to provide at least 30 kcal/kg body wt/day (dogs) or 40 kcal/kg body wt (cats) in a total daily volume tolerated by the animal. It is possible to feed a 20-kg dog three 200-mL meals/day or a cat three 60-mL meals/day and adequately meet nutritional requirements. If anorexia has been persistent for >1 wk, it is advisable to begin feeding smaller volumes more frequently. For example, most dogs can be started with 30-60 mL meals, and most cats with six 20-30 mL meals/day. Several commercially available canned products are calorically dense and (when blended with water) will pass through an 8 French or larger nasogastric or gastric tube. Nasogastric tubes smaller than 8 French require a commercially prepared homogenized liquid. If for some reason a tube cannot be placed, dogs and cats can be maintained by IV solutions that provide adequate calories, protein, electrolytes, B vitamins, and selected trace minerals until access to the small intestine is possible.

Cachexia:
Cachexia, usually present in cases of neoplasia or chronic renal or cardiac disease, appears to be a response to increased catabolism with either normal or decreased appetite. The deterioration of the animal’s condition clearly indicates that nutritional requirements are not being met, and the dietary goal is to increase the caloric density and palatability of the food while meeting the animal’s requirements for protein and other nutrients. The usual management of cachexia is to feed smaller amounts of a more calorically dense (ie, higher fat content) but complete and balanced food more frequently (3-6 meals/day). The form of food (dry or canned) that the dog or cat prefers should be fed. Tube feeding and IV nutritional support (see above) should also be considered if the dog or cat continues to lose weight and condition.

Diarrhea:
This results from increased fluid secretion into, or decreased resorption from, the colon. The etiology should be established, and any intestinal infection or parasites treated. Diarrhea often resolves with the addition of fiber (>10% dry-matter basis in dogs, 5-10% in cats), which modulates intestinal motility, rate of passage, fecal water content, and intracolonic pressure. If dehydrated, the animal should be rehydrated with oral or parenteral fluids, and lost electrolytes replaced. Fat content of the diet is not an issue if there is no steatorrhea, which is rare. Dietary fat content should be adjusted for body condition; however, diets with >12-16% fat (dry-matter basis) should not be necessary. Animals with diarrhea should be offered small, frequent meals (3-6/day). If the animal does not respond within 3-6 wk, a highly digestible, novel protein and carbohydrate diet should be tried.

Congestive Heart Failure (CHF):
One objective in managing CHF is to reduce water retention; restricting sodium intake and lowering sodium levels encourage diuresis. Typical commercial dog and cat foods have a sodium content of 0.45-0.90% (450-900 mg sodium/100 g diet dry matter). Dietary sodium restriction is classified as mild (400 mg sodium/100 g diet dry matter) to severe (240 mg sodium/100 g diet dry matter). In view of these values, commercial dog and cat diets cannot even be classified as mild sodium restriction. Therefore, commercially prepared low-sodium diets or recipes that use low-sodium foods must be substituted. Sodium restriction often requires a special diet, although some manufacturers provide veterinary therapeutic diets for heart disorders. When using a home-prepared diet, all processed meats, cheeses, bread, heart, kidney, liver, salted fats, whole eggs, and snack foods should be avoided. Foods that are reasonably low in sodium include beef, rabbit, chicken, horsemeat, lamb, freshwater fish, oatmeal, corn, and rice.

Failed cardiac contractility may contribute to CHF, and taurine supplementation should be used to exclude a possible depletion of this amino acid in cardiac muscle. Obesity can also be a contributing factor in CHF. Such animals should be placed on a weight management program in addition to sodium restriction. In some instances, edema may give the appearance of obesity and mask emaciation. The edema should first be resolved so that body weight and condition can be evaluated. If the animal is underweight, the food intake should be increased or the caloric content of the diet increased. If renal failure is also present, protein and phosphorus intake must be restricted. Supplementation of carnitine remains somewhat controversial and expensive for long term use.

Constipation:
This results from impaired peristalsis or increased water absorption from the large intestine. The objective of dietary management is to provide a balanced diet with increased amounts of insoluble fiber (10-25% dry-matter basis to effect) in dogs or a balanced diet that is reasonably high in fiber in cats. Such diets increase intestinal volume, stimulate peristalsis, and hold water within the colon. Animals should be fed 2-4 times/day. In dogs, sometimes adding a high-fiber breakfast cereal to the existing diet, 1-10 tbsp to effect depending on the size of the dog, is also effective. In cats, administration of petroleum jelly, 1 tsp (5 mL), PO, once weekly or more often, is helpful in preventing constipation, particularly in cats prone to hairball production. Commercial diets are also available to help manage hairballs and generally contain increased amounts of insoluble fiber.

Diabetes Mellitus:
Most cases of diabetes in dogs and cats are mature onset (type II) and believed due to insulin insensitivity, although insulin-dependent diabetes mellitus is seen. The objective of dietary management is to reduce food consumption and to balance carbohydrate intake with insulin dosage, while slowing the rate of carbohydrate absorption. Reducing diets that are available for dogs and cats are usually high in protein and low in fat and carbohydrates and may help in diabetes mellitus management. To ensure a reasonably constant intake of carbohydrates or nutrients that contribute to blood glucose, a fixed formulation food should be fed. Some believe that minimal carbohydrate should be present in the diet overall, but this approach remains controversial. Because removal of both fat (triglycerides) and carbohydrate (glucose) from the circulation depends on insulin, blood concentrations of these macronutrients are known to affect the amount of insulin required. Consequently, meals should be timed to coincide with peak insulin action, and more than 1-2 meals/day may be required. Many diabetic dogs and cats are overweight and benefit from a weight management program, which is especially useful in cases of type II diabetes.

Feline Lower Urinary Tract Disease (FLUTD):
In this condition, magnesium-ammonium-phosphate crystals accumulate in the urinary tract, together with mucous-like material. There are other etiologic factors, but providing the cat with a diet that has a low magnesium content and that maintains a urine pH of <6.4>Fever:
Fever increases energy requirements due to increased metabolic activity—a 1°F (0.5°C) rise causes an increase in caloric need of ~7 kcal/kg body wt/day. A highly palatable diet should be fed in quantities that can be consumed easily, and the caloric content should be increased by feeding a higher fat diet. Because animals with fever generally have a decreased appetite, offering smaller meals more frequently with personal attention and encouragement may help stimulate intake. Feeding a feline growth diet or a calorically dense recovery-type diet also increases protein and energy intake in smaller feedings.

Gastric Dilatation (Bloat):
Currently, there is little evidence to suggest that certain nutritional practices (eg, feeding soy protein diets or canned versus dry food) lead to the development of gastric dilatation in susceptible dogs.

Head Trauma, Burns, and Respiratory Diseases:
It is unknown whether the metabolic effects and energy expenditure in dogs and cats with severe head trauma, burns with ≥50% loss of skin, or prolonged dyspnea are the same as those in humans with similar conditions. However, it is anticipated that they are. Thus, providing aggressive nutritional support early is essential. Head trauma significantly alters neurologic control of metabolic rate, which is usually increased. Burns and other causes of significant areas of skin loss increase heat loss to the environment, thereby increasing energy needs. Increased respiratory rate and dyspnea are deceptively intense work that also result in increased energy needs. If a dog or cat is in an oxygen cage for >1 day, nutritional support (feeding IV or via gastric tube) must be instituted. In all cases, energy is provided minimally at 30 kcal/kg body wt (dogs) or 40 kcal/kg body wt (cats) and increased in increments of 5 kcal/kg as the condition progresses and if weight loss is apparent. The energy source should be predominately fat (60-90% calories from fat, 10-40% from glucose) because the body metabolism is predominately lipolytic under these conditions, with the liver utilizing fat better than glucose during response to burns or trauma. Protein intake must also be matched with the energy intake to avoid net protein and muscle catabolism. Food that is 30-45% protein and 25-30% fat (dry-matter basis) that is complete and balanced for all other nutrients should be fed using tube feeding. Human baby foods are not suitable for this purpose. These nutritional goals can also be met by parenteral (IV) nutrition.

Hepatic Disease:
Liver disorders are managed by reducing the need for liver function and providing the nutrients necessary for healing and regeneration. In general, diets should provide a protein source of high biologic value and be limited to an amount consistent with the animal’s maintenance needs. Sufficient energy from fat and carbohydrate are needed to minimize dietary protein transamination and deamination for energy and to reduce toxic nitrogenous waste products of protein metabolism. Foods that contain purines and uric acid, such as shellfish, fish meal, spleen, thymus, liver, brain, etc, should be restricted in a further effort to decrease the load of uric acid precursors, which require hepatic metabolism. Frequent feeding of small meals (4-6/day) lowers the amount of nutrients or metabolites requiring hepatic processing at a single time, thereby imposing less metabolic demand on the liver. In general, protein sources equivalent to egg or milk protein in quality are provided at 2-3 g/kg body wt in dogs and 5 g/kg body wt in cats. If ascites or edema is present, the animal should be placed on a restricted sodium diet that contains ~240 mg sodium/100 g diet (dry-matter basis). If blood ammonia levels are increased (hepatic encephalopathy), the protein intake should be restricted to 1-1.5 g protein/kg body wt in dogs and 3-4 g protein/kg body wt in cats. In practice, protein intake is reduced, and the serum ammonia levels are monitored until they return to normal. Arginine is important in the conversion of ammonia to urea. It is present in adequate amounts in most commercial diets. Animals with liver disorders are frequently anorectic. Thus, food consumption and body weight and condition should be monitored. For dogs, a diet high in fat and low in residue should be selected initially, although fat restriction may be necessary to maintain normal feces. Dietary fats are not a source of short-chain fatty acids, which may exacerbate hepatic encephalopathy. Soluble fiber-containing diets may be a problem, depending on the extent of encephalopathy present. Copper should be restricted in dogs at risk of developing copper-induced hepatopathy, and water-soluble vitamins should be increased above maintenance levels. The effectiveness of manipulation of branched chain and aromatic amino acids in dogs with chronic liver disease has not been demonstrated.

Hyperlipidemia in Dogs:
This can be primary or secondary to hypothyroidism, pancreatitis, hepatic disease, diabetes mellitus, nephrotic syndrome, hyperadrenalism, or high-fat diets. Hyperlipidemia is present when blood lipids are increased with or without gross lipemia and probably results from abnormalities in the synthesis or use of plasma lipoproteins. In primary hyperlipidemia, the abnormalities can be familial and might be genetic, as has been suggested in Miniature Schnauzers. Some dogs with hyperlipidemia are asymptomatic. Clinically affected dogs may have recurrent seizures, depression, recurrent pancreatitis, vomiting, acute blindness, corneal opacity, and xanthogranulomas. The goal of dietary management is to decrease the digestion and absorption of fat by feeding a diet restricted in fat (<10%>Malabsorption and Maldigestion in Dogs:
Diseases of the small intestine and pancreas often lead to a vague clinical syndrome characterized by weight loss, vomiting, diarrhea (with or without steatorrhea), and changes in appetite. In such cases, a highly digestible diet that is low in fiber (0-5%), moderate in fat (10-15%) and protein (20-25%), and contains carbohydrate from noncereal byproduct sources is recommended. Supplemental water-soluble vitamins should also be used. In exocrine pancreatic insufficiency, supplementation with a powdered enzyme supplement, mixed with the food a few minutes before feeding, should be considered.

Obesity:
It is estimated that 40-50% of dogs and 20% of cats seen by veterinarians are overweight and that 25% of dogs and 5% of cats are obese. Obesity, or the storage of excess fat, results from an imbalance between calorie intake and expenditure. The principal cause is excessive food intake combined with inadequate exercise. Obesity is regarded as the most common nutritional disorder in dogs. Its incidence increases with age and neutering because there is a reduction of both metabolic rate and physical activity. Similarly, obesity is a common nutritional disorder of neutered, male indoor cats ~6-11 yr old. Some breeds of dogs, including Labrador Retrievers, Dachshunds, and Beagles, are more prone to obesity. Dogs fed homemade meals, table scraps, and snacks have a greater tendency to be overweight than those on an exclusive diet of commercial pet food. Obesity appears to be increasing in frequency, probably due to increased dietary fat levels and caloric density of some foods in conjunction with improved palatability of commercial pet foods. An increasing number of neutered dogs and cats confined to living indoors may exacerbate the problem. Pathologic conditions in dogs that may be associated with obesity include hypothyroidism, hyperadrenocorticism, diabetes mellitus, and insulinoma. Obesity predisposes dogs to other problems, including ruptured cruciate ligaments, dyspnea and fatigue, impaired reproductive efficiency, and dystocia. Pathologic conditions in cats that may be associated with obesity include diabetes mellitus, nonallergic skin conditions, and lameness (ruptured cruciate ligaments). Obesity may also predispose cats to other problems including impaired reproductive efficiency and dystocia.

Dietary management of obesity requires a significant reduction of caloric intake until a normal body weight is achieved. In addition, activity level or exercise should be increased (eg, a regular exercise program for dogs or outdoors regularly for cats) to expend energy and possibly reduce appetite. To begin a weight loss program for canine obesity, the normal or ideal weight for the animal should be estimated and enough food provided to meet 60% of the requirement for the animal’s ideal or normal weight (75% of the necessary caloric requirement for cats). An accurate dietary history should also be obtained to determine the animal’s present daily caloric intake. The most effective diets are those that are nutritionally complete, balanced, and formulated as a reducing diet. These diets should be low in calories and fat (5-8% dry-matter basis). High-fiber diets are also often used to dilute caloric density (10-25% dry-matter basis for dogs, 20-30% for cats). Commercial or homemade reducing diets are preferable to feeding smaller quantities of the normal diet so that dilution of other important nutrients such as protein, vitamins, and minerals does not develop. Small meals may be fed frequently during the day. Table food should be eliminated because it tends to be high in calories; other snacks should be accounted for as part of the total daily ration. When the diet is changed, the new diet should be introduced slowly (over several weeks) replacing 25-30% of the old food weekly and then restricting the volume fed into multiple meals per day. Cats should also be introduced to a new diet slowly, replacing 25-30% of the old food weekly until 100% of the new food is accepted. Afterward, ad lib access to the new food for 2-3 mo is followed by the appropriate restricted amount of food fed as multiple meals per day. In dogs, the rate of weight loss should be ≤2% of body wt/wk for the first few weeks. In cats, the rate of weight loss should be 1-3% of body wt/wk, or more commonly 5% body wt/mo for the first few weeks. As the cat approaches optimal weight, the rate of weight loss per week will decrease. It may be more difficult to reduce the weight of cats that weigh ≥20 lb initially, and owners should be aware that a weight-loss program may take ≥1 yr. Progress should be monitored by weighing monthly, and dietary modifications made if necessary. Frequent monitoring and communication help the owner maintain enthusiasm for a weight-loss program, as does a commitment on the part of the owner to increase the frequency of exercise for their pet (eg, walking, running off leash). The burden of resisting the constantly begging dog or cat under these circumstances can be lessened by feeding small amounts (1 tbsp) several times a day and carefully monitoring future food allotments once the desired body weight is attained. Another tip is to have owners make sure that all the food (including any snacks) offered is placed in the animal’s regular food bowl rather than given by hand. This forces the owner to go to the food dish each time a treat is offered and may reduce the number of between-meal snacks.

Pancreatitis and Parvovirus Enteritis in Dogs:
The goal in treating pancreatitis is to minimize stimulation of the exocrine function of the pancreas until inflammation has decreased. Cases of parvovirus enteritis, which is more common in puppies 3-8 mo old, are often treated similarly. In either case, the dog has multiple episodes of vomiting. A standard treatment is nothing per os (NPO) until vomiting ceases, which can last from 3-15 days. Antibiotic, fluid, and electrolyte therapy during NPO treatment is essential, and IV nutritional support should be instituted if NPO therapy continues for ≥3 days. Adult and young dogs can be nutritionally maintained by IV parenteral solutions that provide adequate calories, protein, electrolytes, B vitamins, and selected trace minerals until oral feeding is possible. When oral feeding can be resumed, a commercially prepared, homogenized liquid diet fed as small, frequent meals (1-2 mL/kg, 3-6 times/day) is the next least stimulatory to the pancreas and best used by a small intestine with an abnormal or absent mucosal surface. The liquid can be fed by syringe by placing the syringe tip in the cheek pouch, lateral to the teeth and gums, with the head in a normal or slightly down position. This method encourages voluntary swallowing with less risk of aspiration. When oral feedings of the liquid diet have been well tolerated for 1-2 days, a moderate-fiber diet (10-15% dry-matter basis), low in fat (5-10%) for pancreatitis or moderate in fat (10-15%) for parvovirus, can be fed in increasing amounts until maintenance intakes have been achieved. Pups with parvovirus should not be fed food sufficient to support growth until feces are normal. Also, because recurrent episodes of pancreatitis are common, feeding a complete and balanced low-fat diet on a continual basis is recommended for longterm management. Obesity and hyperlipidemia are common concurrent problems in pancreatitis cases and should be investigated and resolved.

Renal Insufficiency:
Numerous metabolic abnormalities that may alter an animal’s nutritional status develop in progressive renal failure. These include impaired clearance of nitrogenous products of protein metabolism; impaired regulation of sodium, potassium, and phosphorus; impaired vitamin D metabolism; and often anorexia. The objective of dietary management in renal failure is to lessen the metabolic demands on the kidneys and to diminish metabolic end-products that cannot be readily excreted. The first consideration is to ensure normal water homeostasis. Regardless of whether the animal is polyuric, oliguric, or anuric, water should always be readily available. Increased BUN is lowered by reducing dietary components that produce nitrogen (and urea) as a consequence of hepatic deamination. Supplying energy primarily via feeding relatively more digestible fats and carbohydrates and less protein is recommended. The amount of protein in the diet should be the minimum that meets the requirements imposed by turnover of enzymes and tissue repair and maintains a slightly positive nitrogen balance. In addition, phosphorus intake should be restricted. Diets should have high energy density, with a moderate amount of protein of high biologic value (15-20% in dogs and ~28% in cats). No more than 0.4-0.6% phosphorus and 0.2-0.4% sodium (dry-matter basis), with a balanced calcium level and increased levels of water-soluble vitamins, should be included. These amounts are less than those ordinarily found in many commercial diets, which often necessitates a dietary change. If renal failure becomes more advanced, and the BUN and serum phosphorus concentration can no longer be maintained near normal limits, more energy from fat should be included. Adding ½ cup of fat as cooked beef fat, chicken skin, fat drippings, or fish oil to the diet increases caloric density and improves palatability. This helps to meet the animal’s energy needs with less total food consumed and, therefore, less protein. The criteria used (eg, serum creatinine concentration, BUN) to define when dietary modifications should be made are currently being debated. However, it is easier to change the diet when the animal is feeling reasonably well as opposed to when the animal is anorectic. There is likely to be little harm in changing the diet early in the course of renal disease. Some therapeutic renal diets tend to alkalinize blood pH as acidosis begins, which may minimize the effects of acidosis and help the animal feel more energetic and eat better.

Urolithiasis in Dogs:
Uroliths in dogs most commonly are struvite (magnesium-ammonium-phosphate), calcium oxalate, urate, or cysteine. A definitive diagnosis can be obtained only by stone analysis. A medical protocol using antimicrobials and a calculolytic diet for prevention or dissolution of recurrent stones is an effective alternative to surgery once the stone type is known. The dietary goal is to decrease intake of the mineral constituents and to modify urine pH to discourage stone formation. The dietary profile includes a reduced amount of protein of high biologic value (low in nucleic acids), calcium, phosphorus, and magnesium, with increased salt to encourage frequent urination. An acidic (<7)>7) urine pH is recommended for calcium oxalate, urate, or cysteine uroliths. These nutritional formulations should be used with caution during growth, lactation, and gestation, and in cases of azotemic primary renal failure, congestive heart failure, or liver disease.

Steatitis in Cats:
Steatitis (pansteatitis, yellow fat disease) is seen most often in kittens fed exclusively large amounts of unsaturated fatty acids, oily fish such as tuna or mackerel (packed in oil not water), or diets that do not have an appropriate balance of antioxidants relative to polyunsaturated fats. Clinical signs are anorexia, pyrexia, pain over the thorax and abdomen, neutrophilia, and subcutaneous nodules of necrotic fat. Cats with steatitis should be fed diets restricted in polyunsaturated fatty acids (monounsaturated and saturated fats are permitted) and given vitamin E supplementation at 10-20 mg, bid for 5-7 days. The diet of choice is a commercial food to which vitamin E (α-tocopherol) or other antioxidants have been added.
Notes: Contribution Merck Veterinarian Manual