The domestic cat, Felis catus, evolved from the north African wildcat Felis silvestris lybica and began cohabitating with Egyptians as early as 2300 BCE.1 Although cats have lived closely with humans for many years, when domestication is defined as cultivation and breeding to create a reproductively isolated group, only pedigree cats qualify.² Common domestic cats usually choose their own mates and can still reproduce with wild F. sylvestris when they share common territory.^2,3 With relatively little breeding interference from humans, most pet cats retain adept hunting skills and feeding patterns similar to those of their wild ancestors. Cats are solitary hunters and eat 10 to 20 small prey meals spread evenly over 24 hours.^4,5 Examples of prey include rodents, lagomorphs, birds, and reptiles.⁶ Although domestic cats retain many innate hunting behaviors, they adapt well to controlled feeding situations and can be fed either ad libitum or by meals. Free choice feeding more closely resembles natural feeding patterns. Evidence linking this feeding pattern to feline obesity is mixed. While some studies suggest it is a risk factor for obesity,^7–9 others have failed to show a connection between feeding patterns and obesity.^10–12

In addition, ad libitum feeding makes it more difficult for owners to assess their cat’s appetite, and periods of anorexia may go unnoticed until significant weight loss has occurred. Cats are hunters; therefore, placing food in different locations and using devices to hide food so that it must be sought (e.g., puzzle feeders, Fig. 19.1) can provide environmental enrichment by stimulating predatory drive.

Food preferences in cats are both instinctive and acquired. Taste receptors in cats are specialized for eating meat. For example, taste buds of the facial nerve are very reactive to amino acids but do not respond to many monosaccharides and disaccharides.13 Acquired taste preferences in kittens have been demonstrated through prenatal and postnatal exposure of certain flavors in amniotic fluid and milk of queens.¹⁴ Kittens also learn appropriate food choices by imitating their mothers. One study demonstrated that when weanling kittens (5 to 8 weeks of age) accompanied their mothers as they ate bananas and mashed potatoes, the kittens would later eat those inappropriate foods on their own.¹⁵ Preferences for food texture also appear to be a learned behavior. In a study comparing house cats and outdoor farm cats, the house cats avoided raw meat whereas the outdoor cats shunned dry kibble.¹⁶ Although cats can develop preferences for certain food types on the basis of their experience, they also can grow tired of the same food (known as the “monotony effect”) and often prefer a novel diet as long as it has a familiar texture.^2,16

Mark Twain once said, “If man could be crossed with the cat it would improve the man, but it would deteriorate the cat.” (Notebook, 1894). Cats are unique creatures with novel evolutionary adaptations. The carnivorous nature of the cat has led to anatomic and metabolic modifications. Cats are designed to hunt small prey. Their ears are more attuned to the high-pitched sounds of rodents; they have a large optic cortex to focus on small, quick movements; their retractable claws allow them to stalk prey with soft pads and then attack with claws; they have fewer molars and premolars than do omnivorous dogs; and their jaws have little side-to-side motion for grinding.17 Because feline prey species comprise mostly protein and fat, cats lack salivary amylase for carbohydrate digestion. Because cats evolved eating a highly digestible diet with little fiber and complex carbohydrates, they have shorter intestinal length and absorptive capacity than do dogs and humans.¹⁷

The most notable metabolic difference between cats and more omnivorous species such as humans and dogs is that cats have a much higher requirement for protein. Adult cats require about 4–5 grams of protein per kilogram of body weight compared with 2.6 grams in dogs and 0.8 grams in humans.^18–20 Because cats have evolved eating a diet plentiful in protein and low in carbohydrates, gluconeogenesis from amino acids is used to maintain blood glucose levels.²¹ Dietary protein is also a potent stimulator of insulin release in the cat. Although most animals suppress gluconeogenesis during meals, cats increase hepatic glucose production during the absorptive phase to offset increased levels of insulin.²² Because cats are so dependent on protein for gluconeogenesis, they continue metabolizing amino acids for energy even when protein malnourished. As a result, cats lack the ability to downregulate the production of aminotransferases and urea cycle enzymes in response to low protein intake and can become protein malnourished quickly when anorexic.^22,23 Deficiencies in essential amino acids can lead to severe disease and death. The most dramatic response to an amino acid deficiency is caused by a lack of arginine. Arginine is required by the urea cycle to convert toxic ammonia to urea. Ammonia is a by-product of protein metabolism, and if cats are fed even one meal without arginine, hyperammonemia can occur. Symptoms include vocalization, vomiting, ataxia, apnea, cyanosis, and death within a few hours.⁵ Taurine is technically a sulfonic acid rather than an amino acid and can be synthesized from cysteine in most species. Cats have minimal activity of the enzymes necessary to synthesize taurine and must obtain it from the diet. Taurine is used exclusively to conjugate bile salts into bile acids in cats, and this causes an obligatory loss of taurine even when dietary intake is deficient.²⁴ The most notable symptoms of taurine deficiency in cats are dilated cardiomyopathy and retinal degeneration.^25,26

The carnivorous nature of the wild feline has also led to modifications in fatty acid and vitamin requirements. Arachidonic acid is a fatty acid abundant in animal tissues. Because it is plentiful in the natural feline diet, cats do not have the canine or human ability to synthesize arachidonic acid from linoleic acid. Arachidonic acid is especially important for growth, pregnancy, and lactation.^5,17 Cats and dogs are unable to synthesize vitamin D from sunlight because they lack adequate 7-dehydrocholesterol in the skin. Vitamin D is abundant in animal fat and tissues such as the liver, so deficiencies rarely occur.²⁷ Vitamin A is found only in animal tissues, whereas its precursor, beta-carotene, is synthesized by plants. Cats have limited ability to convert beta-carotene to vitamin A and must ingest the retinol or retinyl ester form of the vitamin (e.g., retinyl acetate or retinyl palmitate).²⁸

ENERGY NEEDS

The cat’s caloric requirement, or daily energy requirement (DER), is a combination of several factors. In the average housecat, most energy is devoted to maintaining basal metabolic functions, known as resting energy requirement (RER). Energy is also expended for exercise, digestion, and temperature regulation. To estimate how many kilocalories a cat should be fed daily, RER is estimated using a cat’s ideal body weight. Unlike muscle tissue, fat tissue utilizes little caloric energy. Therefore, an overweight cat that carries 3 lb (1.4 kg) of extra fat does not need additional calories to support the excess fat mass. RER can be estimated using an exponential or linear equation:

RER (Kcal/day)=(Body weightkg)0.75×70

or

RER (Kcal/day)=(Body weightkg×30)+70

For example, a 10 lb (4.5 kg) cat would have a RER of 217 kcal/day with the exponential equation and 205 kcal/day with the linear equation. Once the RER has been estimated, it is necessary to consider the age, activity, and neuter status of the cat to determine its DER. Life stage factors by which RER can be multiplied to estimate DER can be found in Table 19.1. For example, the RER of an intact male cat is calculated at ideal weight using one of the equations above and then multiplying that number by 1.4 or 1.6.

Table 19.1

Estimated Energy Requirements for Cats at Different Life Stages.a

Life Stage	Factor to Multiply by Resting Energy Requirement
Intact	1.4–1.6
Neutered	1.2–1.4
Obese prone	1
Weight loss	0.8
Senior	1.1–1.4
Geriatric	1.1–1.6
Gestation	1.6–2
Lactation	2–6
Growth <50% of adult weight 50%–70% of adult weight 70% to adult weight Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related Related posts: page Principles of Anesthesia Molecular Assays Used for the Diagnosis of Feline Infectious Diseases Oncology Stay updated, free articles. Join our Telegram channel Join Tags: The Cat Clinical Medicine and Management 2e Mar 30, 2025 | Posted by admin in GENERAL | Comments Off on Nutrition for the Normal Cat Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access