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Volume 50 | Issue 2 Article 6

1988 A Review of Feline Nutrition S. Kantorosinski Iowa State University

W. B. Morrison Purdue University

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Recommended Citation Kantorosinski, S. and Morrison, W. B. (1988) "A Review of Feline Nutrition," Iowa State University : Vol. 50 : Iss. 2 , Article 6. Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol50/iss2/6

This Article is brought to you for free and open access by the Journals at Iowa State University Digital Repository. It has been accepted for inclusion in Iowa State University Veterinarian by an authorized editor of Iowa State University Digital Repository. For more information, please contact [email protected]. A Review of Feline Nutrition

S. Kantorosinski, BS * W. B. Morrison, DVM, MS**

The nutritional.needs ofthe are quite specific In this paper the general principles of feline and differ greatly from the nutritional require­ nutrition will be reviewed. The nutritional needs ments of other species, such as the dog. The cat which make the cat different from other species evolved from a strict and has not had the are highlighted. Certain diseases which have a chance through evolution to change much from nutritional basis are discussed so that they may be its carnivorous nature. Therefore require a more easily recognized and considered as part of much higher intake than an omnivore, a differential diagnosis. Finally nutritional such as the dog. The cat's need for dietary , management as a component ofthe treatment for , preformed A, and high protein specific conditions such as feline urological makes it characteristic and different from many syndrome, renal failure and anorexia is considered. other species. It is only in recent years that the nutritional perculiarities of the cat are beginning Protein to be recognized and researched. Protein is necessary in the diet ofany animal to As occurs in other animal species, disease in cats supply the essential amino acids, to supply the may result frorn prolonged feeding ofunbalanced nitrogen necessary to synthesize those amino acids diets. Diets composed of a single food item may considered nonessential, and to supply nitrogen result in deficiency disease or toxicity. It is not for the formation ofpurines, pyrimidines, heme, uncommon to see nutritional hyperparathyroidism and creatinine. 7 The cat and fox are two species in cattery who are fed homemade diets of known to require a higher protein intake than most high meat content. 1 Deficiencies of one or more other mammalian species. In fact, one author may result in diseases such as pansteati­ suggests that adult cats require almost five times tis, malnutrition, and central retinal degener­ the amount of protein as adult dogs. 8 In the cat ation. 2 ,3,4 Many of these conditions may be it seems that a fixed amount of dietary protein is corrected with dietary alterations ifthe practitioner always broken down for energy. 6,7 After amino recognizes that the disease is nutritionally related. groups are removed from amino acids the result­ The use of nutrition as part of the medical ing keto acids can be used for energy or glucose management of certain disease conditions is also production. Unlike most other mammals the cat increasingly being used. Management of feline cannot adjust its catabolic to shifts in urologic syndrome through alterations in diet is levels of dietary protein. 6,7 These enzymes are now accepted practice. 4, 5 Dietary alteration is always set to handle a medium to high level of used to prevent progression of renal destruction dietary protein even though there may be too low in . 4 ,6 So for the veterinary practi­ a level of protein in the diet. Insufficient intake tioner an understanding of feline nutrition is ofprotein may result in a deficiency of the essen­ important in prevention ofdisease as well as treat­ tial amino acids as well. Deficiency of the essential ment and management of disease. amino acids leads to decreased food intake and weight loss. * Dr. Kantorosinski is a 1988 graduate of the College of Veterinary Medicine at Iowa State University. There are varied values given for the amount of ** Dr. Morrison was formerly an associate professor ofClinical protein necessary in the feline diet. One source Sciences at the College of Veterinary Medicine at Iowa State University. His current address is the College of Veterinary recommends 25 - 30 % protein in the diet on a dry Medicine, Purdue University, West Lafayette, IN 47907. weight basis; that is, if the protein is of good

Vol. .50, No. 2 95 biologic value (70-90 biologic value).4 This would cient in the diet ammonia accumulates in the mean 25 % of the in the diet would be blood. Cats on arginine restricted diets have shown supplied as protein. A much lower value of 12.5 % signs of soon after a meal. The is given by another source saying that ifa satisfac­ cats display any of the following signs: hyper­ tory level could be met this diet could activity, hyperesthesia, , emesis, ptyalism, support body weight and nitrogen needs in adult apnea, cyanosis, and sometimes death. Since cats. 9 This value is still higher than that required arginine is involved in the metabolism ofthe waste by other mammals. The National Research Council products ofprotein metabolism some say that the (NRC) has recommended as a minimum 240 arginine requirement increases when a high pro­ grams of protein/ kg diet (on dry basis) for grow­ tein diet is fed as compared to a diet where protein ing kittens, which is about 20% of a very palat­ is near the minimum requirement level. 8 Arginine able, high quality diet.7 deficient diets occur rarely under natural circum­ Protein, like , increases the palatability ofthe stances. diet. It is best to avoid protein from a single protein source because this frequently leads to an Cats are very sensitive to a dietary deficiency of imbalance of amino acids as well as resulting in taurine. Other species are able to make taurine the cat becoming addicted to a single item diet. from whereas cats have a very limited The most critical period for ascertaining that the ability to use methionine to synthesize taurine. In cat has sufficient protein in the diet is just after addition there is a constant loss of taurine in the weaning. The NRC recommends about 20% pro­ conjugation of bile salts. Cats predominantly use tein (on a dry basis), whereas, another source taurine in conjugating bile salts, whereas, other recommends 30-40 % ofthe diet be protein during mammals are able to use either taurine or glycine this critical period.4,7 The recommendation of in bile salt conjugation. The demand for taurine the NRC is a minimum value and relates to a is increased even more during growth as muscle purified diet of high biologic value. mass increases. Most taurine in the body is found It is imponant to realize that all the amino acids in three main tissues: bile, the , and the ingested are not readily available to the body. olfactory bulb. 3 In one experiment cats fed a Processing offoods may affect the digestibility of taurine-free diet for eleven months showed rapid the food. For example, the digestibility ofsoybeans decrease in their plasma taurine levels and about is increased during processing since the cooking half showed central retinal degeneration. 11 Visual inactivates trypsin inhibitors found in soybeans. 7 acuity in the cats did not appear to be affected. On the other hand, the drying of meats can The lesions are in the central area ofthe retina and decrease the nutritive value ofthe protein. 7 When the normally bright yellow tapetum becomes dark protein is heated in the presence ofreducing sugars and granular and later a hyper-reflective focal the availability of amino acids is reduced. 7 Also lesion develops as photoreceptor cells are lost. 7 during storage, in the presence ofpoly­ With chronic deficiency the entire fundus appears unsaturated lipids can be oxidized which reduces atrophied. Vision does not seem to be affected the levels of amino acids especially methionine, until retinal degeneration is advanced; therefore , and . 7 Therefore, ifthe diet routine ophthalmoscopic exam on cats may be a is composed ofa high quality protein consider that good practice. Changing the diet to one with about 80-90 % is available; if it is made up of a adequate taurine will not reverse the damage but low quality protein consider 60-70% available. 7,10 it will help prevent further progression of the Of the essential amino acids there are two that disease. Taurine is high in meat, seafood, and distinguish the cat as being quite different from milk. I2 It is low in vegetables and most dog other mammalian species. Arginine, which most foods. I2 Cases ofcentral retinal degeneration have animals can synthesize to some degree in the occurred when cats were fed dog foods or when kidney, is necessary in the diet of cats. Taurine, a diet had casein as the only source of protein. another amino acid, has received much attention Reasons given for feeding cats were the in the literature since studies have shown a taurine lower cost, some cats preferring dog food over cat deficiency frequently leads to central retinal de­ food, and the instructions ofveterinarians who felt generation in cats. 3,1l,I2 Each of these amino dog food reduced the incidence offeline urolithi­ acids will be discussed further. asis. 12 Since taurine is also found in the olfactory Arginine is necessary for the conversion of bulb in rather high levels it is suggested that smell ammonia to urea. If arginine is lacking or defi- or taste may also be affected but this is uncenain. 3

96 The Veten·nary Student Fat sary for normal reproduction and blood platelet Fat in the diet provides a concentrated source aggregation. of energy. It is also essential for absorption of fat In one study male cats fed a diet deficient in soluble , for providing the essential fatty the essential fatty acids for about two years showed acids, and increasing the palatability of the diet. extensive testicular degeneration. 14 They found Cats can tolerate and digest high levels of fat in that iflinoleate was included in the diet degener­ the diet quite well. ation of the testes did not occur. When linoleate Cats are influenced by the amount and source was supplied in the diet levels of arachidonate in of dietary fat. Commercial canned cat foods tend the testes increased which was thought to be due to have a higher percentage of crude fat on a to the conversion ofsome linoleate to arachidonate dry matter basis than dry commercial cat foods. by the testes. 14 The levels of arachidonate in the Usually there is from 10-40°10 crude fat in canned plasma did not increase even though it seemed diets as compared to 10-12 °10 in dry diets. Many apparent that the testes converted some linoleate cats seem to prefer about 20-30 °10 crude fat rather to arachidonate. 14 So it seems that linoleate can than a much lower or higher percentage. The type help prevent testicular degeneration in a cat of fat is also important in palatability. Cats tend consuming a diet deficient in arachidonate. In the to prefer animal over vegetable fats. Diets high female cat on an arachidonate free diet, adding in levels of hydrogenated coconut oil were refused linoleate to the diet did not help her reproduc­ by many cats. The cats preferred hydrogenated tive function. She could not bear kittens unless a beef tallow diets over high levels ofhydrogenated certain level of arachidonate was present. 14 coconut oil. 7 Chicken and turkey fats are known Sources of these essential fatty acids differ. The to increase palatability. Commercial cat food richest source of arachidonate is the lipid portion manufacturers also learned that cats could be of organ meats. 16 Warm water fish and shellfish stimulated to eat diets with fat content at 4 °10 on are other good sources. oil contains a dry basis if the fat was sprayed on the surface arachidonate but it also contains a 22 carbon chain of pelleted foods. 13 which seems to interfere with Since fat provides about 2.25 times the metabol­ arachidonate .16 The possibility of developing an izable energy as protein or , adding arachidonate deficiency is greatest in cats fed dry fat to the diet greatly alters the energy concentra­ cat foods since they have a lower fat content then tion of the diet. Concern is over the fact that cats commercial canned cat foods. Vegetable oils lack will take in sufficient energy but not sufficient arachidonate and most rendered animal fats if protein, vitamins, or minerals when a diet is limited to 10°10 fat in the diet would not provide supplemented with fat. If adjustments are not the necessary arachidonate. 16 A good source of made in these other nutrients the result may be is safflower oil. In one study cats on a cat that is malnourished due to a deficiency in a diet deficient in these essential fatty acids one or more of these nutrients. developed severe fatty liver, fat in the kidneys, dystrophic mineralization of the adrenal glands, Fat is necessary in that it provides linoleic and testicular degeneration, and hyperkeratosis of the arachidonic acids, the two fatty acids considered skin. 16 These deficiency signs disappeared when essential in cats. Most other mammals can convert safflower oil (as a means of supplying linoleate) linoleate to arachidonate by desaturation and was added to the diet. In this same study some elongation which occurs in the liver. 14 The ability cats were fed diets containing hydrogenated of the cat to convert linoleate to arachidonate is coconut oil, safflower oil, and chicken fat and fatty very minimal, 7 so both fatty acids are considered livers developed despite the presence ofhigh levels essential in the cat diet. Linoleate is not simply oflinoleate. The fatty livers were thought to have a precursor to arachidonate but is in itself essential resulted from the effects of the medium-chain for certain body functions. If linoleate was defi­ in hydrogenated coconut oil. The cient in the diet, scaly skin, enlarged fatty livers researcher suggests that hydrogenated coconut oil and loss of water transepidermally occurred. It is may have accentuated an known that linoleate has a function in the struc­ deficiency, which has also been shown to occur in turing of membranes for proper growth, lipid rats eating high levels of hydrogenated coconut oil. transport, and normal skin and coat condition. The level of fat in the diet beyond what is neces­ Arachidonate also has a structural function and is sary to supply these two essential fatty acids has a precursor to prostaglandin, PGE2 .15 It is neces- not been demonstrated. 7

Vol. 50, No. 2 97 Certain vitamins are fat soluble and require the of the cervical vertebrae, ribs and long bones.3 presence of some fat in the diet for absorption. To avoid the possibility of hypervitaminosis no These fat soluble vitamins are A, D, E, and K. more than one ounce of liver a day should be fed to an adult cat. 13 Since is a fat soluble Vitamins vitamin, excesses are not excreted but stored in the The vitamin requirements of the cat are quite body, especially in the liver. Therefore, deficiency specific. Cats in general have a higher need for the is rare. B-complex vitamins than other animals. The values is another fat soluble vitamin that ofminimum requirements ofsome B-vitamins are deserves special attention since occasionally 2-8 times greater for cats than dogs. For example, deficiencies occur. Diets high in polyunsaturated

, , provides the prosthetic fatty acids as contained in may increase group of transaminases and since cats have a high the vitamin E requirement three or four times. 7 transaminase level their requirement for B6 may Vitamin E stabilizes the unsaturated lipids. When be four times that of the dog.6 is a B­ large amounts of unsaturated fatty acids are taken vitamin which has received attention due to its easy in without sufficient (vitamin E) destruction during cooking and storage. High peroxidation of depot fat may occur and later fat losses can occur when canned foods are processed. necrosis.6 The adipose tissue becomes yellow to Up to eighty percent of thiamine can be lost in orange-brown in color and firrn. This condition is processing so manufacturers should supplement called pansteatitis or yellow fat disease. Most com­ the food with several times the thiamine require­ mercial cat foods have vitamin E added but these ment to insure adequate levels after processing.7 additional quantities become insufficient if the Thiamine deficiency can also result from prolonged owner is supplementing the commercial foods with ingestion of uncooked fish which contains high proportions of red tuna or some other fish. thiaminase. Thiamine deficiency is characterized Some fish oils, such as cod liver oil, are very high by ataxia, cerebellar tremors, loss ofrighting in the in unsaturated fatty acids and low in antioxidents air, and seizures. 17 Cats with thiamine deficiency such as vitamin E. Clinical signs of pansteatitis will tend to keep their head ventroflexed on the which may be seen are anorexia, pyrexia, tender­ sternum when they are suspended by the hind ness of palpation of the abdomen and thorax. limbs. Normally a cat put in this position will Small nodules may be present in the subcutaneous dorsoflex its head. Diagnosis can be confirmed by tissues. Biopsy of the subcutaneous fat may show giving thiamine orally or intramuscularly and fat cell necrosis and infiltration by neutrophils. observing for improvement which usually occurs One case study alerts practitioners to the fact that within a few hours. pansteatitis can resemble feline infectious perito­ Cats are also characterized by their inability to nitis in its clinical appearance. 2 An eight month convert Beta-carotene to vitamin A.7 Cats must old male presented with ascites, anorex­ have preformed vitamin A in the diet, unlike many ia, weight loss, low grade fever, and diarrhea. The other mammals who have the ability to convert conditon progressed to a chronic debilitating Beta-carotene to the needed vitaminA.7 This need disease resembling FIP in clinical appearance. The for preformed vitamin A is part of the strict author stresses the importance ofconsidering pan­ carnivorous nature of the cat. Considering that steatitis as a differential diagnosis when a cat liver is one ofthe highest sources of the preformed presents with effusive abdominal disease and fever vitamin, the cat as a carnivore, had no need to which is antibiotic resistant. 2 Other diseases on retaiit an ability to convert Beta-carotene to vita­ the differential list for these clinical signs should min A since the diet in most cases provided an include and lymphosarcoma. Labor­ abundance ofpreformed vitamin A. Beta-carotene atory data should allow differentiation of these is found in many vegetables and is not toxic if diseases. Pansteatitis can usually be treated success­ consumed in large amounts. One the other hand, fully with alpha-tocopherol. vitamin A consumed in large amounts in the diet is very toxic. Cats fed a diet consisting mainly of liver may be receiving toxic doses of vitamin A Minerals which frequently presents as skeletal deminerali­ Minerals are needed by the body to maintain zation. There may be extreme tenderness ofjoints acid-base balance, tissue structure, and osmotic especially of the cervical skeleton due to bony pressure. They are also essential in the function exostoses that develop along muscular insertions of many systems. Even though minerals

98 The Veterinary Student in a food may meet the minimum requirements, and the kittens selectively eat the horsemeat. In the bioavailability must also be considered. Phytic the wild, cats would eat a predominantly meat diet acid and chitin can greatly reduce the availability but would be provided when the bones of minerals in a feed. If the in a diet of small rodents were also consumed. is largely plant derived it should only be considered Clinical signs ofnutritional hyperparathyroidism about 30% bioavailable since it is likely to be are lameness, limping or reluctance to move. 1 bound to phytate to a great degree.7 , a There may also be signs of posterior paresis, bone component of many body enzymes, may and joint pain, and constipation. 1 Radiographic need to be tripled in amount in a diet containing findings show loss of bone density, possibly pelvic large amounts of phytate and fiber. 7 In phytate­ deformities, and pathologic fractures especially of containing diets which contain excess calcium, zinc the vertebrae. 1 Serum calcium and phosphorus is bound in the gut in an insoluble zinc-calcium­ levels are usually within the normal range. Occa­ phytate complex and therefore not available for sionally blood clotting times may be extended. absorption.7 Adding supplements of several different minerals to the diet may result in Formulating Diets For Cats problems due to the interaction of different Formulating a diet requires that sufficient minerals. An excess ofone mineral in the diet may nutrients and energy be available to supply the decrease the absorption ofanother.7 For example, needs of the animal depending on whether the an excess of phosphorus in the diet lowers the needs are for growth, maintenance, or bioavailability of . 7 In the table of minimum . The diet must be iooked at in terms of requirements (Table 1) the NRC suggests that its biologic value. This is determined by the values of iron, , and be mutiplied edibility, digestibility, and metabolizability of the by a factor of 1.3 to help correct for decreased diet. 4 If a cat consumes all the diet the food is bioavailability.7 Zinc and should be considered one hundred percent edible. Digesti­ 7 multiplied by a factor of 1.5. bility is determined by measuring the amount of Secondary hyperparathyroidism is a condition the , for example, protein eaten minus which results when the levels of calcium and the amount of protein recovered in the feces. 4 phosphorus are altered in the body. Diets low in Metabolizable energy is the gross energy of the calcium or very high in phosphorus may lead to nutrient minus the energy of the feces and . 4 1 this disease. It is essential that these minerals be From these measurements the biologic value is maintained in a specific ratio in the diet. A calcium determined. to phosphorus ratio of 1: 1 to 2: 1 is thought to be acceptable. Diets composed primarily of cardiac quantity of nutrients absorbed and retained and skeletal muscle can upset this ratio greatly. Biologic Value = Beef heart has a calcium to phosphorus ratio of quantity absorbed 1:40. 1 Horsemeat has a ratio of 1: 10. 1 The great excess of phosphorus in these foods can lead to The nutrient requirements of the National inadequate absorption ofcalcium which results in Research Council are listed in Table 1. These a hypocalcemia. Hypocalcemia stimulates the requirements are those for purified feline diets that parathyroids to release parathormone in an attempt have a very high bioavailability. The bioavailability to restore the serum calcium to normal levels. of natural ingredients used in cat foods will vary Parathormone acts on bone, kidneys, and the from the purified diet. In general, protein diges­ intestine in its attempt to increase the calcium and tibility and amino acid bioavailability of ingre­ % decrease the phosphorus levels. The adult cat has dients used in cat foods will not exceed 90 • 7 If 18-40 grams of calcium in its skeleton and these there is a high amount of collagen in the food, stores can be used to restore serum calcium to a digestibility may only be 50 %. The National normal level. 7 The increased serum parathormone Research Council hopes to correct for these differ­ causes more bone resorption which results in a loss ences in bioavailability by suggesting that their ofbony mass. Increasing numbers ofcases ofsecon­ minimum values for concentration of amino acids dary hyperparathyroidism are seen in catteries be multiplied by a factor 1.3.7 They recommend where breeders believe high meat diets produce that their minimum requirements for the B­ healthier and faster growing kittens. In some vitamins in the table be multiplied by 1.6 to help catteries this may occur when kittens are offered extrapolate the figures in the table to practical dry cat food free choice in addition to horsemeat, diets.7 Thiamine requires additional precautions

Vol. 50, No. 2 99 due to loss during cooking and processing. meals frequently throughout the day. Domestic Just as imponant as the biological value ofa diet cats on a free-feeding method were usually found are the different requirements ofeach stage ofthe to nibble randomly throughout the day.I8 Some life cycle: mainly growth, maintenance, reproduc­ would eat 10-20 small meals in a 24 hour period. tion and lactation. The NRC in its table has given Most researchers agree that cats can regulate their the minimum requirements for growing kittens. caloric intake quite well no matter what type of Due to the fact that research into the area offeline food is available. Most cats will voluntarily restrict nutrition has only begun to increase in recent years, their energy intake to that energy which is needed knowledge in this area is still limited. The NRC by the body. One study found that cats fed vary­ has not set minimum requirements of nutrients ing diets were able to adjust their intake after a for maintenance and reproduction. They believe very short time so that mean intake at each meal that the minimum requirements listed for kittens remained constant. I8 This occurred even when are adequate for other stages ifcertain changes are some meals were of low caloric density and made. For maintenance the levels of protein and required a bulky intake to satisfy caloric needs. If methionine should be reduced as noted in the needed a cat can easily meet its energy needs on table, and for reproduction vitamin A and taurine one large meal per day. It is important that meals levels should be increased. Energy requirements be of good quality but not overly palatable. differ during the various stages ofa caes life. Miller and Allison recommend the following energy requirements for growing kittens and adult cats: 250 kcal/ kg body weight at 5 weeks of age Cat Foods 100 kcal/ kg body weight at 30 weeks of age Selection ofa well balanced commercial cat food 85 kcal/ kg body weight at 50 weeks of age is not as easy as it may seem. There are two main (active cat) methods by which food is judged to be nutrition­ ally adequate. The manufacturer may claim on the An inactive, confined cat may need only 70 label that the food meets the standard require­ kcal/ kg body weight of energy per day. 7 Energy ments set by the NRC. This is one way in which requirements increase during gestation such that the nutritional value of the diet can be assessed. most researchers believe that queens require about But statements of the nutrient value of a diet tell 25 % more energy especially in the later stages of nothing about the diet's palatability, bioavail­ pregnancy. It is not uncommon for queens to lose ability or protein quality. Feeding trials, which are weight during lactation even though they have free a second method ofjudging the quality of a diet, access to a very palatable diet. In one study often are better indicators than NRC requirements. 6 If lactating queens in the first six weeks postpartum a food is labeled "complete, perfect, a scientific energy requirements increased form 90 to, 270 kcal or balanced ration for cats" it must meet the NRC metabolizable energy / kg maternal body weight. 7 requirements or have been proven in feed trials. 4 Reading the nutritional statement on the label can be quite helpful. Also note the label for guaran­ Feeding Behavior tees and analyses. There should be a guaranteed The feeding behavior of the cat is also quite minimum percentage of protein and fat and characteristic. Cats usually prefer to eat alone guaranteed maximum percentage for fiber and without competition from other cats or . It is water. These are minimums and maximums and suggested that iftwo cats are in a household, feed do not necessarily indicate the quantity of these each in separate bowls which are placed at differ­ substances in the food. Economically it may not ent areas of the room. 13 If a dog is in the house­ be recommended buying a canned food with great­ 4 hold it may be best to place the eat's bowl in some er than 75 % moisture. If a canned food has less elevated location that the dog can not reach. The than 5 % fat or if a dry food has less than 7 % fat cat is an adaptable and opponunistic feeder which the caloric density may be considered too low. 4 was required in its evolution from a wild carnivore. The list ofingredients on the food gives a general In the wild it had to stalk and capture its food so idea of what is in the food and whether vitamin meals depended on the type ofwildlife in the area. and mineral supplements have been added. It is Ifwildlife caught was rather large in size it would recommended that a good quality food be pur­ mean that meals would be large and probably chased rather than supplementing a poor quality infrequent. If the area supplied an abundance of diet. Cats frequently develop a preference for one mice the cat would probably adapt to having small type diet over another. These preferences develop

100 The Veterinary Student as a result of previous dietary experiences and are acid over neutral or alkaline foods. "Digest" is not due to a requirement for certain nutrients. made by enzymatic breakdown of a variety of Commercial cat foods come in a variety offorms. animal products such as poultry by-products, liver, There are canned ration, canned gourmet, semi­ fish, and beef lungs. 4 The action of the enzyme moist, and dry types offoods available. The diges­ is then stopped by adding an acid. Eventually the tibility of canned food is usually higher than that acid provided by the digest must be excreted by of dry foods. Canned foods have from 72-78 °/0 the kidney. moisture. The canned ration type foods are many It can be seen that each of the commercial cat times labeled as nutritionally complete and they foods has its advantages and disadvantages. Some supply energy from protein, fat, and owners choose to feed their cat a homemade type in fairly substantial quantities. The gourmet diet. This, even though well intentioned, is not canned foods are designed to add variety to the recommended since frequently the cat is fed one diet but not formulated to act as a sale source of predominant food which leads to an imbalanced nutrients. They are frequently nutritionally in­ diet. One course recommends choosing a canned complete and energy is supplied mostly through ration type food ofa manufacturer which is labeled protein and fat. Gourmet canned foods are usually to provide complete and balanced nutrition. 13 the most expensive type food and are highly palat­ Otherwise it is suggested that a mixture of two or able, such that cats seem to become addicted to more types of foods be fed to provide the neces­ one certain variety. sary nutrients. So, for example, feed one-half the Semimoist cat foods are intermediate in energy requirement as a canned food and provide moisture between the canned and dry foods. They the remaining energy as a dry food. Also during contain less fat than canned foods and generally periods when extra energy is needed such as have more cereal than canned foods so more energy growth, pregnancy and lactation it may be wise is supplied by carbohydrate and less by fat. Semi­ to provide a diet which is more energy dense. One moist foods have products ad'ded to stabilize the study compared a dry cat food with 21 °/0 fat to product, maintain water levels, and prevent a leading diet with 12 °/0 fat. The diet with spoilage since refrigeration is not required. Such the higher fat content resultd in 10°/0 higher birth things as sugar, , sorbates, and weights, 40°/0 greater kitten survival, and a 30°/0 propylene glycol may be added. To control bac­ greater weight gain in kittens from birth to terial growth, pH is maintained using phosphoric weaning. 6 acid. Use of phosphoric acid may increase phos­ phorus levels in the food enough to lead to problems in cats susceptible to feline urologic THE USE OF NUTRITION syndrome. 4 IN MANAGEMENT OF DISEASE Dry foods are composed of 7-12 °/0 moisture and are mainly carbohydrate and protein with very low Feline Urologic Syndrome fat content. Dry foods have substantial quantities Dysuria, hematuria, cystitis, and urinary tract ofcereal grains, milling by-products and soybeans obstruction are all signs which may be seen with added with poultry by-products, fish meal, feline urologic syndrome. The incidence of the "digest" and animal fat present to increase syndrome is quite high. In fact, some statistics say palatabilty. Crude protein is 28-36 °/0 -on a dry that as high as one out of ten cats seen in veteri­ matter basis, less than that in most canned foods nary hospitals have problems relating to FUS. 7 The but very similar to the content in the semimoist incidence seems fairly equal in males versus foods. Dry foods have the advantages of costing females, although most urinary obstructions occur less, offering a wide variety of protein sources in males. Without proper dietary or medical therefore, decreasing chances of cats becoming management it is estimated that 50-70°/0 of all addicted and being easy to store and feed. Some cases will have a recurrence. 6 Various factors have nutrients may be destroyed in processing and later been suggested as causes of FUS, such as: infec­ in post-processing oxidation. tion; alkaline urine; age of castration; endocrine "Digest" is frequently being used in dry cat imbalance; high ash in the diet; high dietary foods. This is a liquid which is sprayed on the ; phosphate or nitrogen; low water exterior of dry cat food to increase palatability by intake; ; dry cat foods; confinement; and providing flavor and acidity. Cats seem to prefer less frequent urination. 7 The cause is likely to be

Vol. 50, No. 2 101 several factors acting together and may not always tion ofa mucoid plug causing urethral obstructIon. be the same set of factors. The mineral content of the urine is an impor­ Urine pH is an imponant factor in urinary crystal tant factor in urinary crystal formation. The formation. In the wild, cats normally produce an minerals in urine can be inBuenced by diet, acid urine with a pH of 6.0-7.0 due to their high efficiency ofdigestion, urine volume, and kidney meat diet. The vegetable ingredients in cat foods functioning. 5 Altering diet is one way to change frequently result in a neutral or more alkaline the mineral content of the urine. Most commer­ urine. After a meal, urine pH increases and cial cat foods that are made with soybean meal and remains elevated for one hour or more as a result bone meal are high in magnesium. Most cat foods of the "alkaline tide" phenomenon. Many on the market are 4-18 times the minimum researchers believe that the increase in alkalinity magnesium levels recommended by the NRC due which normally occurs after eating plus the increase to the type of ingredients used in making the in minerals in the urine from food being digested food. 6 Realize that magnesium levels in the food may lead to a crystal formation in the urine and can closely relate to urinary magnesium concen­ FUS. To minimize the crystal formation some tration but there are several precautions to be researchers recommend keeping the urine pH considered. For one, the magnesium in the food below 6.6.7 Below a pH of 6.6 crystals may not be highly bioavailable and much less is remain in solution; above a pH of 7.1 crystalhza­ absorbed and utilized than expected. ~ion spontaneously occurs. 7 Studies are being done to see whether it is bet­ The caloric density of the food is very impor­ ter to feed a cat free choice or to feed 1-2 large tant. Dry cat foods on a dry matter basis may meals per day. Feeding free choice usually means contain the same level of magnesium as canned the cat is eating 10-20 small meals a day and with foods. Since the energy concentration ofdry foods each meal the urine pH rises and remains elevat­ is less; cats must eat more dry foods to meet ed for a short period. If one or two large meals their needs and, therefore, get higher levels of are fed, the urine pH increases to a greater degree magnesium. 7 ,19 with each large meal and remains elevated for a High levels of ash in the diet are frequently longer period. The question is whether one situa­ associated with high levels ofmagnesium. But this tion is more conducive to stone formation than the is not always true since ash is considered to be all other. Remember that in regard to urine pH sever­ the noncombustible materials in a diet; so it not al factors are involved, not only is the feeding only includes magnesium but sodium chloride and interval important but also the type of food fed calcium salts. Still some persons believe that if a and the mineral composition of the diet. cat is FUS susceptible the ash in the diet should 4 The majority of cases of FUS have calculi, be less than 5% on a dry matter basis. This state­ microcalculi, or crystals present in the urinary ment can be made as long as the magnesium and tract. 6 Bacteria and viral infections are rarely phosphorus levels are also low in this low ash diet. involved and when a urinary tract infection is Urinary mineral levels cannot be considered present it is thought to be secondary and not a without also considering urine pH. If urinary pH 0 cause of FUS. In 81.9 / 0 of the cases of FUS the is near neutral and magnesium levels are high in calculi are composed ofstruvite. 6 Struvite contains the diet the incidence of FUS increases. 7 If the magnesium, ammonium and phosphate. The urine pH is acid the high magnesium levels are urine of a cat is usually quite high in ammonia usually of no problem. Also if urinary pH is high and phosphorus due to its high protein diet. The FUS may result with low urinary magnesium levels of magnesium and phosphorus in the urine levels. 6 So urinary magnesium concentration and relate closely to the intake of these minerals in the urinary pH are related in the development of diet. Three factors seem to be imponant in calculi FUS.5,6,7 formation. 6 The first factor being a high concen­ Another factor in crystal formation is the length tration of these calculi-forming constituents in the oftime urine remains in the urinary tract. Cats are urine. Secondly is the pH of the urine which able to highly concentrate urine and go long should be favorable for crystal formation. The third intervals without voiding. Being a descendent of factor important in calculi formation is that urine the desert cat of North Africa, cats can drink less be in the urinary tract for a prolonged time. Calculi water and concentrate urine to a greater degree may cause an urethral obstruction or irritate the than other mammals. 6 The amount of water urinary tract leading to mucus secretion and forma- consumed is affected by salt intake, condition of

102 The Veterinary Student kidneys, age, and dry matter consumed. 4 It was reduced so as to maintain a blood urea nitrogen found that cats consume less water in relationship ofless than 60 mg/ dl. 6 Reduced protein is recom­ to dry matter on dry foods than on canned foods. 4 mended in patients showing clinical signs of Therefore, urine volume is also less. Water intake uremia that are azotemic, hyperphosphatemic, and is not only an important consideration in FUS, but in moderate to severe renal failure. 6 In patients also in renal failure, and sulfonamide adminis­ not showing signs of uremia a low protein diet is tration. 4 controversial. Many sources recommend restricting Commercial dry cat foods have been considered dietary protein in all animals with reduced renal a possible cause ofFUS. They are higher in vegeta­ function regardless ofthe severity. Higher protein ble ingredients than most other types offoods and diets have been shown to increase glomerular filtra­ therefore, lead to a more neutral and even slight­ tion rate and renal blood flow which may be harm­ ly alkaline urine. Dry cat foods have a similar ful and lead to further renal damage. Restricting magnesium level on a dry matter basis as canned protein in the diet not only reduces the wastes of foods but their lower caloric density requires a protein metabolism, but may reduce progression greater intake to meet energy needs. It was also of renal failure. 6 A restricted protein diet also mentioned that cats seem to consume less free decreased dietary phosphorus and therefore, may water to dry matter on a dry food diet than a decrease the risk of hyperparathyroidism and canned diet. Some researchers also believe that osteodystrophy. As chronic renal failure develops since dry foods tend to be higher in fiber more the kidney loses the ability to excrete phosphorus water is excreted in feces and therefore, less which leads to a high serurn phosphorus level. As through formation ofurine. 6 These factors would a result serum parathormone levels increase which lead one to suspect that cats on a dry food diet may cause further damage to the renal tubules. would have an increased incidence ofFUS. Many To prevent the use ofthe body's own proteins for studies do support this view. 4,6,7 One study done energy, make sure the animal is consuming suffi­ with specific pathogen free cats on dry food diets cient calories in the diet. Feeding small meals did not find any association between a dry food several times a day instead of a single large meal diet and increased incidence of FUS. 20 Note­ may also help reduce catabolism of body protein. wonhy in this study was the fact that cats were kept Make sure that plenty of drinking water is always on a dry diet for only 4.5 months and then available. Ifsevere, proteinurea is present and the euthanized. animal has hypoalbuminemia, it may be necessary In summary, FUS seems to have a multifactor­ to supplement each four ounces offood with one ial etiology. 21 Factors ofurinary pH, urine mineral egg or two tablespoons ofcottage cheese. 4 Ifpoly­ concentration, and length of time urine remains uria exists there may be excessive loss ofB-vitamins in the bladder are known to affect calculi forma­ in the urine so diets formulated for use in renal tion. Since dietary changes can alter these factors failure patients frequently are supplemented with and possibly lead to a decreased incidence and B-vitamins. Proper dietary management in renal recurrence of PUS concentrating on nutritional failure may slow progression of the disease and management may be a good path to follow until reduce uremic signs. further research is available. More study is need­ ed using prospective clinical trials to assess the effect of diet alterations on FUS. Hepatic Disease The aims of dietary management in hepatic Renal Failure disease are- to restore liver glycogen and reduce the Nutritional management is a very important workload on the liver. 4 Energy provided in the part of managing renal failure. Proper dietary form of starch or simple sugars is tolerated well. alterations can slow the progression ofrenal disease The liver helps in the metabolism of the "rastes and decrease signs of uremia. The goal of dietary of protein breakdown, therefore, protein in the management should be to reduce the end-products diet should be at a moderate level so the demands ofprotein metabolism which are eliminated by the on the liver will be lessened. If the protein intake kidneys, such things as protein metabolites and is too high in an animal with hepatic failure, phosphorus. Some suggest that in renal failure less encephalopathy may occur. 6 Proteins in the diet than 25 0/0 ofthe calories in the diet should be from should be of high biologic value such as eggs and protein. 4 Another source says protein should be liver. Insure that the diet provides adequate adequate in amount to meet requirements but calories so that the body does not utilize body fat

Vol. 50, No. 2 103 and protein stores for energy. Ifbile salt excretion Most cats who are physically able to eat will when is impaired there is a decreased ability to use fats given 0.1-0.5 mg diazepam intravenously. Have so restrict fats in the diet to less than 1.5 % •4 food available at the time of injection. Then 1-2 Avoid use of medium chained triglycerides in mg is given orally to maintain appetite. This hepatic failure since they are mainly metabolized should not be used for more than two days. in the liver. Certain fatty acids may also induce Anorexia is a very challenging problem but recog­ encephalopathy if the diseased liver cannot nize that lack ofnutrient intake ofeven a few days metabolize them.6 Ascites which occurs in liver adversely affects the entire body. The body's ability failure may be due to portal hypertension which to fight the disease or heal the trauma is lessened results in loss of vascular fluid and activation of when nutrients are absent. the renin-aldosterone system. 6 In this case, the ascites is not a result ofhypoalbuminemia. There­ fore, if ascites is present, a low sodium diet may be recommended. These measures will decrease the Obesity stress placed on a poorly functioning liver and help relieve some of the clinical signs of liver failure Obesity is a problem in cats as it is in many other which may be present. domestic species,. Obese cats are frequently on a diet of gourmet canned foods and may refuse to Anorexia eat other types of commercial foods. The owner Infection, nutritional deficiencies, metabolic may be supplementing the canned food with high disorders and trauma frequently lead to anorexia caloric table scraps, and may be unaware that a in cats. Ifprolonged, anorexia may lead to hepatic problem even exists. Initially a good history must lipidosis and jaundice.6 The aim is to maintain be taken including a good diet history of types of an intake ofprotein and energy to meet the needs food eaten, amounts, and intervals of feeding. A of the body and to prevent the development of complete physical exam should be done to rule out a fatty liver. The safest and easiest way to feed an health problems. Since talking about obesity, even animal is via the . Feeding when it concerns a family , can be a very sensi­ through the gut is less likely to lead to a fatty liver tive issue try and develop a rapport with the client. and increased production ofsecretory IgA improves Explain that the incidence of certain diseases is resistance to infection. 6 So ifthe gut is functional increased in obese individuals. Since the success use it as the means of nutrient intake whenever of the animal achieving its optimal body weight possible. Appetite stimulation, force feeding and depends mainly on the efforts ofthe client, make tube feeding are methods that can be used. Ifthe sure the client is a part of the decision making. gut is nonfunctional parenteral means must be Determine an optimal body weight for the animal used instead. To stimulate appetite warming the and estimate the time required to safely attain that food enhances aroma and may help in encourag­ weight. With the client set realistic short term ing the cat to eat. If nostrils are plugged, clean goals, such as the goal for weight loss after one them. Being able to smell the food is very impor­ week. It is considered safe for a cat to lose about tant in appetite stimulation. Providing a very one-half pound the first week and about three palatable diet that is the same as the one provid­ pounds over twelve weeks.4 Initially try a diet ed in the animal's home environment may help. which is 20-30 % lower in calories than the pre­ Force feeding may be used if it does not result in vious diet6 • If this results in no weight loss or a a high level ofstress. It may work in a debilitated minimal loss then change to a diet providing animal if done gently and with patience and 65-70% of required calories to maintain a cat at reassurance. Cats that are stronger will usually fight its optimal body weight (about 35 calories/pound this procedure. Tube feeding may be recommend­ ofoptimal body weight/day).4 to lose one pound ed since it is faster and less stressful than force of body fat caloric intake must be decreased by feeding. Blend one-halfcan ofa formulated, high 3500 kcal. A diet high in fiber and low in fat is energy diet and 3/4 cup water together then strain recommended for weight loss, generally less than the mixture through a kitchen strainer. 6 Admin­ 10 % fat (on dry basis) and greater than 15 % ister enough of the mixture to meet the eat's fiber. 6 It may be necessary to gradually introduce energy needs in two to three feedings per day. the new diet. With lots of client encouragement, Another method which is occasionally used on a patience and teaching the goal of weight loss can very temporary basis is to administer diazepam. be achieved.

104 The Veterinary Student *Table composed by the National Research Council. amounts of these nutrients should be included to ensure that Table 1 the minimum requirements are met. The minimum require­ ments presented in this table assume availabilities similar to those Minimum Requirements for Growing Kittens present in purified diets. (units per kg of diet, dry basis)a bNo requirement for fat is known apart from the need for Nutrien~ Unit Amount essential fatty acids and as a carrier offat-soluble vitamins. Some fat normally enhances the palatability <;>f the diet. Fatb cAssuming that all the minimum essential amino acid Linoleic acid g 5 requirements are met. mg 200 dThe minimum requirement increases with pro­ Proteinc (N x 6.25) g 240 tein intake. eThis minimum should be adequate for a moderate to low­ Arginine g 10 fat diet. It may be expected to increase three-to four-fold with Histidine g 3 a high PUFA diet, especially when fish oil is present. g 5 fThese vitamins may not be required in the diet unless g 12 agents or antivitamin compounds are present in g 8 the diet. Methionine plus cystine g 7.5 gCholine is not essential in the diet but if this quantity of (total sulfur amino acids) is not present the methionine requirement should be Methionine g 4 increased to provide the same quantity of methyl groups. plus g 8.5 hA dietary requirement for myo-inositol has not been Phenylalanine g 4 demonstrated for the cat. However, almost all published studies Taurine mg 400 in which purified diets have been used have included myo-inositol at 150 to 200 mg/kg diet and no studies have tested g 7 a myo-inositol-free diet. Tryptophan g 1.5 g 6 Minerals Calcium g 8 Phosphorus g 6 Magnesium mg 400 REFERENCES Potassiumd g 4 Sodium mg 500 Chloride g 1.9 1. Pedersen NC: "Nuu-itional Secondary Hyperparathyroidism ~ted Iron mg 80 in a Cattery with the Feeding of a Fad Diet Copper mg 5 Containing Horsemeat." Feline Practice. Vol. 13, No.6: Iodine ug 350 19-26. 1983. Zinc mg 50 2. Summers BA, Sykes G, Martin ML: "Pansteatitis mimick­ Manganese mg 5 ing infectious peritonitis in a cat." Journal ofthe Amer­ ug 100 ican Veten'nary Medical Association. Vol 180: 546-549. Vitamins 1982. Vitamin A (retinol) mg 1 3. Hayes KC: "Nutritional Problems in Cats: Taurine Defi­ Exc~." (Cholecalciferol) ug 12.5 ciency and Vitamin A Canadian' Veten'nary Jour­ Vitamin Ee (- tocopherol) mg 30 nal. 23: 2-5. 1982. Vitamin Kf (phylloquinone) ug 100 4. Morris ML: Feline Dietetics, Nutritional Management in Thiamin mg 5 Health and Disease. Topeka, Kansas: Mark Morris As5oci­ mg 4 ates, 1981. 5. Morris Animal Foundation. "FUS and Foods." Feline Vitamin B6 (pyridoxine) mg 4 mg 40 Practice. Vol. 14, No.5: 47-48. 1984. mg 5 6. Lewis ill, Morris Jr. ML, Hand MS: Small Animd Clin­ ~tes, Folacin (folic acidf) ug 800 ical Nutrition. Topeka, Kansas: Mark Morris Biotinf ug 70 1987. 7. National Research Council. Nutrient Requirements of Cats, (cyanocobalamin) ug 20 Cholineg g 2.4 Revised ed. 1986. Washington, D.C.: National Academy Myo-inositolh Press, 1986. 8. Rogers QR, Morris JG: "Do Cats Really Need More Pro­ tein?" Journal ofSmall Animd Practice. 521-531. Sept. 1982. aBased on a diet with an ME concentration of 5.0 kcal/ g dry 9. Burger IH, et al.: "The Protein Requirement of Adult matter fed to 10-to-20-week-old kittens. Ifdietary Cats for Maintenance." Feline Practice. Vol. 14, N,'). 2: is greater or lesser, it is assumed that these requirements should 8-14. 1984. be increased or decreased proponionately. Nutrient requirement 10. Kendall PT, Smith PM, Holme DW: "Facrors affecting levels have been selected based on the most appropriate optimal digestibility and in-vivo energy content of cat foods." Jour­ response (i.e., growth, nitrogen retention, metabolite concen­ noI ofSmall Animd Practice. 538-554. Sept. 1982. tration or excretion, lack ofabnormal clinical signs, etc.) of kit­ 11. Burger IH, Barnett KC: "The taurine requirement of the tens fed a purified diet. Some of these requirements are known adequate amounts rather than minimum requirements. Since adult cat." Journal ofSmall Animd Practice. 533-537. diet processing (such as extruding or retorting) may destroy or Sept. 1982. impair the availability of some nutrients, and since some 12. Aguirre GD: "Retinal Degenerntion ~ted with the nutrients, especially the trace minerals, are less available from Feeding of Dog Foods to Cats." Journal ofthe American some natural feedstuffs than from purified diets, increased Veten"nary Medical Association. 172: 791-7%. 1987.

Vol. 50, No. 2 105 13. Kronfeld OS: "Feeding Cats and Feline Nutrition." Con­ 18. Thome C]: "Feeding behavior in the cat - recent ad­ tinuing Education Article #6. Vol 5, No.5: 419-423. vances." ]oumal ofSmoIJ Animal Pmctice. 555-562. Sept. 1983. 1982. 14. MacDonald MI., et aI.: "Effetts of Iinoleate and 19. Fineo DR, Barsanti JA: "Diet-Induced Feline Utethral Arnchidonate Deficiencies on Reproduction and Spennaro­ Obstruction." Veterinary ainics ofNorth Ameni:a: Small genesis in the Cat." The ]oumal ofNutrition. Vol. 114, Animal Practice. Vol 14, No.3: 529-536. 1984. No.4: 719-726. 1984. 20. Fabricant CG, Lein DH: "Feline Urolithiasis Neithet 15. Rivets JPW: "Essential fatty acids in cats. ]oumd ofSmoIJ Induced nor Exacerbated by Feeding a Dry Diet." ]oumal Animo! Pmctice. 563·576. Sept. 1982. ofthe American Animo! Hospitd Association. Vol. 20: 16. MaeDonaId MI., et aI.: "Essential fatty acid requirements 213-220. 1984. of cats: Pathology of =tia1 fatty acid deficiency." 21. Osborne CA, et aI.: "Redefinition of the Feline Urologic American ]oumal of Veterinary Research. Vol 45, No.7: Syndrome: Feline Lower Urinaty Tract Disease with Heter­ 1310-1317. 1984. ogeneous causes." Veterinary ainics ofNorth Ameni:a: 17. Tanwar RK: "Seizures M;ociated with Thiamine Deficiency Small Animal Practice. Vol. 14, No.3: 409-438. 1984. in a Cat." Feline Pmctice. Vol 14: 10-11. 1984.

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106 The Veterinary Student