Nutritional Peculiarities and Diet Palatability in the Cat

Cats have become the most popular companion animal in Western Europe. Unlike other domestic animals, cats are strict carnivores and this influences both their nutritional requirements and food preferences. Cats have very high protein requirements and their diet must contain some nutrients, such as arginine, taurine, niacin, vitamin A and arachidonic acid. Besides its nutritional value, a diet for cats must also be highly palatable. This paper offers a quick overview of feline nutritional peculiarities and the factors that influence food palatability in cats.     

Nutritional peculiarities and diet palatability in the cat

Cats have become the most popular companion animal in Western Europe. Unlike other domestic animals, cats are strict carnivores and this influences both their nutritional requirements and food preferences. Cats have very high protein requirements and their diet must contain some nutrients, such as arginine, taurine, niacin, vitamin A and arachidonic acid. Besides its nutritional value, a diet for cats must also be highly palatable. This paper offers a quick overview of feline nutritional peculiarities and the factors that influence food palatability in cats.     

Evaluation of sodium bisulphate and phosphoric acid as urine acidifiers for cats.

Eighteen cats were used to compare the urine acidifying properties of sodium bisulphate to phosphoric acid. Acidifying agents were added at one of three concentrations (0.4, 0.6, or 0.8%, as-is basis). Cats were offered a commercial diet to determine basal urinary pH, and then again for a 1 week period between blocks 1 and 2. Cats were acclimated to the diets for 6 days, and urine samples were collected on day 7 at 0, 4, and 8 h postfeeding to obtain pre- and postprandial urinary pH. Intakes of diets containing sodium bisulphate tended (P < 0.07) to be lower than intakes of diets containing phosphoric acid. Cats consuming the 0.8% phosphoric acid diet had higher (P < 0.05) food intakes than cats consuming either the 0.4 or 0.6% phosphoric acid-containing diets. There was significant (P = 0.01) linear and quadratic response for food intake in cats consuming the sodium bisulphate-containing diet. Cats consuming the 0.4 and 0.8% phosphoric acid-containing diets tended (P = 0.07) to have higher water intakes than cats consuming the 0.6% phosphoric acid-containing diet. There were no differences (P > 0.05) in urine pH and specific gravity between cats fed the different acidifier types. Cats consuming the 0.6% phosphoric acid-containing diet tended (P = 0.07) to have a higher urine pH 8 h post-feeding than cats consuming the 0.4 and 0.8% phosphoric acid-containing diets. Urine pH was highest at 4 h post-feeding except for cats fed the 0.4% sodium bisulphate- and the 0.6% phosphoric acid-containing diets. No differences (P > 0.05) between acidifiers were found in faecal score or in faecal dry matter and organic matter concentrations. A quadratic response was detected in faecal score for cats consuming the phosphoric acid-containing diets. Cats consuming the 0.6% phosphoric acid diet tended (P = 0.06) to have a lower faecal score than cats consuming the 0.4 and 0.8% phosphoric acid diets. For faecal dry matter, a linear trend was detected in cats consuming the sodium bisulphate (P = 0.08) and phosphoric acid-containing (P = 0.04) diets. Sodium bisulphate and phosphoric acid generally behaved in a similar fashion when incorporated in dry cat diets.     

Influence of feeding on serum feline trypsin-like immunoreactivity.

OBJECTIVE: To determine whether feeding causes a change in feline trypsin-like immunoreactivity (fTLI) in serum from healthy cats. ANIMALS: 6 healthy domestic shorthair cats. PROCEDURES: For the first 12 days of the study, 3 cats were fed a high-protein, high-fat (diet 1), and the other 3 were fed a maintenance (diet 2). On day 12, diets were switched, and cats were fed the other diet for the remaining 12 days of the study. On days 11 and 23, food was withheld for 24 hours, and baseline serum fTLI was measured. Cats were offered food equivalent to half their daily caloric maintenance requirements, and serum fTLI was measured 1, 2, 4, 6, 12, and 24 hours later. Uneaten food was removed after 1 hour. RESULTS: Overall mean +/- SD serum fTLI was 22.7 +/- 5.8 micrograms/L when cats were fed diet 1 and 21.1 +/- 5.0 micrograms/L when cats were fed diet 2. There was no significant difference in serum fTLI over time or between diets. However, there was a statistically significant, but clinically unimportant (mean increase, 1.7 micrograms/L), increase in serum fTLI, compared with baseline values, 1 hour after cats were fed diet 2 but not when cats were fed diet 1. CONCLUSIONS AND CLINICAL RELEVANCE: A maintenance diet may cause a clinically unimportant increase in serum fTLI 1 hour after feeding in healthy cats. Results suggest that for healthy cats, it is not necessary to withhold food before collecting samples for determination of fTLI in serum. Whether feeding changes fTLI in serum from cats with disorders of the exocrine portion of the pancreas remains to be determined.     

Assessment of the neurologic effects of dietary deficiencies of phenylalanine and tyrosine in cats

OBJECTIVE: To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats. ANIMALS: 53 specific pathogen-free black domestic shorthair cats. PROCEDURE: Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for < or = 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats. RESULTS: After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were consistent with sensory neuropathy with primary axonal degeneration. Changes in hair color were detected in cats from all groups receiving < 16 g of phenylalanine plus tyrosine/kg of diet. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that chronic dietary restriction of phenylalanine and tyrosine in cats may result in a predominantly sensory neuropathy. In cats, the long-term nutritional requirement for phenylalanine and tyrosine appears to be greater for normal neurologic function than that required in short-term growth experiments. Official present-day recommendations for dietary phenylalanine and tyrosine in cats may be insufficient to support normal long-term neurologic function.     

Effect of dietary protein quality and essential fatty acids on fatty acid composition in the liver and adipose tissue after rapid weight loss in overweight cats

OBJECTIVE: To examine effects of dietary protein quality (casein [CA] vs corn gluten [CG]) and dietary lipids (corn oil [CO] vs oil blend [OB] rich in long-chain polyunsaturated fatty acids [LCPUFAs]) on fatty acid composition in liver and adipose tissue after weight loss in overweight cats. ANIMALS: 24 ovariohysterectomized adult cats. PROCEDURE: Cats were allowed ad libitum access to a high-quality diet until they weighed 30% more than their ideal body weight. Cats were then randomly assigned to 1 of 4 weight-reduction diets (6 cats/diet) and were fed 25% of maintenance energy requirements per day. Diets consisted of CG-CO, CA-CO, CG-OB, and CA-OB, respectively, and were fed until cats lost weight and returned to their original lean body mass. Liver biopsy specimens and samples of perirenal, subcutaneous, and abdominal fat were obtained and analyzed for fatty acid content. RESULTS: Following weight loss, fatty acid composition of the liver and adipose tissue was primarily affected by protein quality in that cats fed CA had significantly higher percentages of 20:4(n-6) and 22:6(n-3) fatty acids than those fed CG. Cats fed the CG-CO diet had the lowest concentrations of LCPUFAs, suggesting that dietary lipids and protein quality each influence fatty acid composition in tissues. CONCLUSIONS AND CLINICAL RELEVANCE: These data provide direct evidence that dietary protein quality alters fatty acid composition of tissues during weight loss in cats. The fatty acid patterns observed suggest that protein quality may alter fatty acid composition through modulation of desaturase activity.     

Influence of dietary protein and lipid on weight loss in obese ovariohysterectomized cats

OBJECTIVE: To determine effects of dietary lipid and protein on development of hepatic lipidosis (HL) and on physical and biochemical indices following rapid weight loss in cats. ANIMALS: 24 ovariohysterectomized cats. PROCEDURE: Cats were fed a high energy diet until they gained 30% of their ideal body weight and then randomly assigned to receive 1 of 4 weight-reduction diets (6 cats/diet) at 25% of maintenance energy requirements per day. Diets contained a low or high quality protein source and a lipid source deficient or sufficient in long chain essential fatty acids (LCEFA). Serum and plasma samples and liver biopsy specimens were obtained for biochemical analyses and determination of hepatic lipid content before and after weight gain and during and after weight loss. RESULTS: Irrespective of weight-reduction diet fed, all cats lost weight at a comparable rate (4.51 to 5.00 g/d/kg of obese body weight). Three cats developed hepatic lipidosis. Significant changes in plasma insulin, cholesterol, triglyceride, and serum glucose concentrations were detected after weight gain and weight loss in all diet groups, but values for these variables did not differ among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Cats can lose 25 to 30% of their obese body weight over 7 to 9 weeks without developing overt clinical signs of HL, provided that weight-reduction diets are highly palatable, contain a high quality protein, have a source of LCEFA, and are fortified with vitamins and microminerals. However, rapid weight loss may increase risk factors associated with development of diabetes mellitus.     

Nutritional Problems in Cats: Taurine Deficiency and Vitamin A Excess

Two nutritional problems of the cat are reviewed. One represents a deficiency of taurine, the other vitamin A toxicity. Taurine deficiency in cats is insidious because the progressive retinal degeneration induced may go unnoticed until the damage is advanced and irreversible. Both rods and cones undergo degeneration along with the underlying tapetum lucidum. The hyperreflective focal lesion is easily observed in the area centralis with an ophthalmoscope and has been previously identified as feline central retinal degeneration. This lesion is not reversed by taurine supplementation, even though the remaining retina may be saved from further degeneration. The cat requires dietary taurine, found in meat and fish, because it cannot synthesize enough to meet demands for bile acid conjugation and tissue metabolism, especially those of muscle and central nervous system.

Vitamin A toxicity is not commonly observed in cats but may occur if cats are fed beef liver in which appreciable vitamin A is stored. Cats exhibit muscle soreness and hyperesthesia, especially along the neck and forelimbs where bony exostoses of cervical verterbrae and longbones are common. The diagnosis is readily made from radiographs. The response to removal of vitamin A from the diet is generally rapid and, unless the toxicity has been chronic in young kittens, recovery is generally satisfactory.

     

A Retrospective Study of 77 Cats With Severe Hepatic Lipidosis: 1975–1990

The physical, clinicopathologic, and survival rates of 77 cats with severe spontaneous hepatic lipidosis are detailed in this report. Cats were subdivided into groups designated as idiopathic lipidosis if no other disease process was recognized, or secondary lipidosis if another disease process was diagnosed. Cats were also subdivided into groups designated as survivors or nonsurvivors on the basis of successful recuperation at 4 months after initial diagnosis. Differences between disease and survival groups were evaluated for significance. Overall, more female cats and middle-aged cats were affected. Presenting complaints of vomiting, anorexia, weakness, and weight loss were common. Physical assessment of most cats showed obvious hepatomegaly, jaundice, dehydration, and a weight loss ≥ 25% of usual body weight. Neurobehavioral signs indicative of hepatic encephalopathy, other than ptyalism and depression, were rare. Clinicopathologic features are characterized by hyperbilirubinemia and increased activities of serum ALT, AST, and ALP, with only small if any increase in γGT activity. Clinical features distinguishing cats with hepatic lipidosis from those with other serious cholestatic disorders include absence of hyperglobulinemia and low γGT activity relative to ALP activity. Although coagulation tests were abnormal in 45% of cats tested (n = 44), few cats showed clinical bleeding tendencies. Most cats received prophylactic vitamin K₁ therapy. Forty two cats received aggressive nutritional and supportive care and of these 55% survived. Cats with idiopathic disease were significantly younger, had significantly higher ALP activity and bilirubin concentration, and had a slightly better survival rate than cats with secondary lipidosis. Low PCV, hypokalemia, and an older age were significantly related to nonsurvival. Because of the variety of diets and food supplements used in case management, the influence of nutritional factors on survival could not be evaluated. (Journal of Veterinary Internal Medicine 1993; 7:349–359. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Impact of macronutrient composition and palatability in wet diets on food selection in cats

Cats are obligate carnivores adapted to high‐protein diets, but are commonly fed diets rich in carbohydrate. The aim of this study was to examine the food intake choices of cats when diets with different protein and carbohydrate contents were offered. Thirty‐nine cats participated in voluntary dietary intake studies. Four foods were formulated to provide between 24% and 53% of metabolizable energy as protein, between 43% and 11% as carbohydrate and holding dietary fat constant with a contribution of approximately 36%. Foods were offered either singly to evaluate voluntary food intake or in pairs to compare food intake between pairs of diets. Cats regulated their macronutrient intake to attain an overall diet composition that provided 53% of metabolizable energy as protein, 11% as carbohydrate and 36% as fat. The protein contribution corresponded to approximately 6 g of protein/kg body weight/day. High‐protein/low‐carbohydrate diets were always eaten preferentially over low‐protein/high‐carbohydrate foods. When low‐protein/high‐carbohydrate diets were offered, cats limited their food intake to limit daily carbohydrate intake to less than 3 g of carbohydrate/kg body weight. This carbohydrate ceiling may limit protein and even energy intake when only low‐protein/high‐carbohydrate diets were offered. The inclusion of palatability enhancer in the diets increased food intake but did not change protein or carbohydrate intake patterns, indicating that macronutrient intake can be regulated regardless of the use of palatability enhancers in cats. We conclude that cats can discriminate between diets based on macronutrient composition and regulate their intake to maintain maximal protein intake but limit carbohydrate intake.     

Dietary patterns of cats with cardiac disease

OBJECTIVE: To determine nutrient intake and dietary patterns in cats with cardiac disease. DESIGN: Prospective study. ANIMALS: 95 cats with congenital cardiac disease or primary cardiomyopathy. PROCEDURES: Owners completed a standardized telephone questionnaire regarding their cat's diet and a 24-hour food recall to determine daily intake of calories, fat, protein, sodium, magnesium, and potassium. RESULTS: Of the 95 cats, 18 (19%) had a history of congestive heart failure and 73 (77%) had no clinical signs of cardiac disease. Fifty-five percent (52/95) of cats had concurrent disease. Inappetance was reported in 38% (36/95) of all cats and in 72% (68/95) of cats with a history of congestive heart failure. Most (57% [54/95]) cats received treats or table scraps on a regular basis. Approximately half the cats were receiving orally administered medications, supplements, or both. Only 34% (32/68) of owners used food to administer medications to cats. Cats consumed more than the Association of American Feed Control Officials (AAFCO) minimums for protein, sodium, potassium, and magnesium, and nearly all cats consumed more than the AAFCO minimum for fat. Daily nutrient intake was variable for all of the nutrients assessed. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary intake in cats with cardiac disease was variable, but results for dietary supplement use, food use for medication administration, and treat feeding were different from those found in a similar study of dogs with cardiac disease. This information may be useful for treating and designing nutritional studies for cats with cardiac disease.     

Feline pansteatitis revisited: hazards of unbalanced home-made diets

Pansteatitis is caused by the consumption of high levels of unsaturated fatty acids and/or the insufficient intake of vitamin E, leading to inflammation of adipose tissue. This disease has been related to fish-based diets. However, non-conventional diets must also be considered. The authors present case records of two cats with pansteatitis, for which diet consisted mostly of pig's brain, comparing them with eight cases of disease in cats eating mainly oily fish. Cats fed pig's brain did not show clinical signs, while cats eating oily fish presented inappetence, depression, reluctance to move and subcutaneous nodules painful on palpation. Cats eating pig's brain did not show any change in blood parameters, while cats fed oily fish presented leukocytosis and anaemia. Histological examination confirmed pansteatitis in all cats, independently of the diet. All animals except one of the cats eating oily fish recovered after medical treatment and change of the feeding regime.     

Feline struvite urolithiasis: factors affecting urine pH may be more important than magnesium levels in food

Eighteen male cats were fed either a canned complete diet or a commercially available dry pelleted diet or the same dry diet containing 1.6 per cent ammonium chloride. The daily food and water intake of four of these cats was measured. Urine samples were taken at random and the pH and the presence of struvite crystals in their sediment estimated. In some samples in which the pH was less than 7.0, and struvite crystals were absent, the pH was increased to 7.0 and any sediment was examined for struvite. No spontaneous struvite was seen in urine samples (pH 5.8) from cats fed the canned complete diet but when its pH was raised to 7.0, 46 per cent of these samples showed struvite. Cats fed the dry pelleted diet had urine of higher pH (7.55) and 78 per cent of the samples contained struvite crystals. Cats fed this diet supplemented with ammonium chloride had a urine pH of 5.97 and only 9 per cent contained struvite crystals but when the pH was adjusted to 7.0 all the samples showed struvite crystals. Energy intake was similar on all three diets but the intake of dry matter was greater on the dry diets. Liquid water intake was greater on the dry diets but total water intake was greatest on the canned complete diet. The intake of magnesium, calcium and phosphate was greater on the dry diets. It is concluded that urine pH is a more important controller of struvite precipitation than mineral intake.     

Body water content and turnover in cats fed dry and canned rations.

Body water content and total body water turnover in cats fed commercially available dry food and then given canned rations were determined with tritiated water. Cats during the feeding of either ration did not differ in body water content or turnover. Cats during the feeding of the dry ration derived a greater fraction of their total water turnover from drinking water, and these cats drank more water per gram of dry matter intake than when fed the canned ration. On the basis of total water intake, however, those given the canned ration had significantly greater water intake per gram of dry matter; also, their total water turnover per gram of dry matter was greater. Compared with other animals, cats have a similar ratio of body water to body solids, but the rate of water turnover per unit of body weight is slower.     

Clinical Nutrition in Gerontology: Chronic Renal Disorders of the Dog and Cat

The recent advances in the nutrition of companion animals has resulted in a longer possible life-span for dogs and cats and an improvement in their quality of life. Numerous studies about geriatric animals show that an aging dog or cat requires a specific nutritional formulation that considers the metabolic changes associated with age. A correct diet plays an important role in the treatment of some chronic pathologies in aging animals, particularly those for which the aging process modifies the organ function. A correct diet can provide therapeutic support to the administration of drugs that can sometimes compromise organ function. In the present study, we identify key aspects of the clinical nutrition during chronic renal disorders of dogs and cats, diseases with an elevated incidence and a major cause of mortality in geriatric animals. The aim of nutritional treatment for dogs and cats affected by chronic renal disorders is to improve the quality and length of life, assuring an adequate amount of energy and slowing the progression of renal failure. To improve treatment efficacy it is necessary to prepare different dietary rations during the various stages of disease, on the basis of clinical signs and laboratory data.

     

Comparison of corn gluten meal and meat meal as a protein source in dry foods formulated for cats

OBJECTIVE: To compare the nutritional value of corn gluten meal (CGM) and meat meal (MM) as a dietary source of protein in dry food formulated for adult cats. ANIMALS: 8 healthy adult cats (4 males and 4 females). PROCEDURE: Diets containing CGM or MM as the main protein source were each fed for a 3-week period in a crossover study. Digestibility and nutritional balance experiments were conducted during the last 7 days of each period. Furthermore, freshly voided urine was obtained to measure urinary pH, struvite crystals, and sediment concentrations. RESULTS: Daily food intake and dry-matter digestibility were significantly higher for the MM diet. Fecal moisture content also was higher for the MM diet. Apparent nitrogen (N) absorption and N retention were higher for the MM diet, even when values were expressed as a percentage to account for differences in N intake. Urinary pH, struvite activity product, number of struvite crystals in urine, and urinary sediment concentrations were not different between diets. Retention of calcium, phosphorus, and magnesium was lower for the CGM diet, and cats lost body calcium and magnesium when fed the CGM diet. CONCLUSIONS AND CLINICAL RELEVANCE: Meat meal was superior to CGM as a protein source in dry foods formulated for cats, because dry-matter digestibility and N utilization were higher for the MM diet. In addition, net loss of body calcium and magnesium for the CGM diet suggests that mineral requirements increase when CGM is used as a protein source.     

Effects of a synthetic facial pheromone on behavior of cats

OBJECTIVE: TO evaluate the effects of a synthetic feline facial pheromone (FFP) on behavior and food intake of healthy versus clinically ill cats. DESIGN: Original study. ANIMALS: 20 cats were used in each of 2 studies. In each study, 7 cats were considered healthy, and 13 cats were determined to be clinically ill. PROCEDURE: In study 1, cats were assigned either to exposure to FFP (treated group; 4 healthy, 6 ill cats) or to exposure to the vehicle (70% ethanol solution; control group; 3 healthy, 7 ill cats). Cats were placed in a cage containing a small cotton towel that had been sprayed with FFP or vehicle 30 minutes previously. Cats were then videotaped for 125 minutes, and food intake was measured during this period. Videotapes were scored at 5-minute intervals for various behaviors. In study 2, cats were categorized in 1 of 2 groups; group 1 (2 healthy, 8 ill cats) had a cat carrier placed in their cages, and group 2 (5 healthy, 5 ill cats) did not. All cats were exposed to FFP, and 24-hour food intake was measured. RESULTS: Differences between behaviors of healthy versus clinically ill cats were not identified. In the first study, significant increases in grooming and interest in food were found in cats exposed to FFP compared with vehicle. For all cats, significant positive correlations were detected between grooming and facial rubbing, walking and facial rubbing, interest in food and facial rubbing, eating and facial rubbing, grooming and interest in food, and grooming and eating. In the second study, 24-hour food intake was significantly greater in cats exposed to FFP and the cat carrier, compared with cats exposed to FFP alone. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that exposure to FFP may be useful to increase food intake of hospitalized cats.     

Clinical evaluation of commercially available urinary acidification diets in the management of idiopathic cystitis in cats

OBJECTIVE: To compare recurrence of signs of lower urinary tract disease (LUTD) in cats with idiopathic cystitis that were fed the dry or canned formulation of a commercial diet designed to result in production of an acidic urine. DESIGN: Prospective trial. ANIMALS: 54 client-owned cats with idiopathic cystitis that was diagnosed on the basis of a history of abnormal micturition, abnormal results on urinalysis, radiography, or cystoscopy, and lack of an alternative diagnosis. PROCEDURE: Cats were assigned to be fed the canned or dry formulation of the diet. Reevaluations conducted at 2 and 16 weeks, and at 6 and 12 months included a physical examination, CBC and serum biochemical analysis (except week 2), blood gas analysis, and urinalysis. Regular telephone contacts were also made. The study was discontinued after 12 months or if signs of LUTD recurred. RESULTS: Signs of LUTD did not recur in 16 of 18 cats fed the canned diet, and 17 of 28 cats fed the dry diet (chi 2, P < 0.05). Seven cats were reevaluated at recurrence. Owners of remaining cats in which signs of LUTD recurred declined to have their pets reexamined. A different problem (bacterial urinary tract infection) was identified in only 1 cat on reevaluation. Eight cats were lost to follow-up evaluation. CLINICAL IMPLICATIONS: Feeding this commercial canned urinary acidifying diet may reduce the proportion of cats with idiopathic cystitis that will have recurrence of signs of LUTD within a 12-month period.     

Immunological relationship between the New Zealand A and the Australian T strains of infectious bronchitis virus as measured by cross-immunisation tests in tracheal organ cultures from immunised birds

AIM: To determine if exogenous oestradiol or the phyto-oestrogen genistein could reduce food intake in male and female cats fed ad libitum that had been allowed to accrue excessive bodyfat following neutering.

METHODS: Sixteen adult (eight female, eight male) cats were neutered and allowed to increase their bodyweight (BW) through feeding ad libitum of a complete and balanced dry diet. Oestradiol was injected subcutaneously for 5-day periods in incremental doses (0.25–4 µg per cat), then food intake was recorded, and vaginal cytological changes were observed in females. Similarly, genistein was administered orally for 5-day periods in incremental doses (5–100 mg/kg).

RESULTS: In males and females, both oestradiol (p<0.001) and genistein (p=0.037) significantly reduced food intake during treatment, and the minimum daily doses that produced a significant effect were 0.5 µg and 100 mg/kg, respectively. The minimum daily dose of oestradiol that produced a significant effect on food intake was not associated with changes in vaginal cytology over the 5-day treatment period.

CONCLUSIONS AND CLINICAL RELEVANCE: Gonadal oestradiol appeared to be a key modulator of food intake in both male and female cats, and replacement of oestrogen to neutered cats via oestradiol or an oestrogen surrogate such as genistein has potential for reducing the prevalence of obesity in neutered cats.