1. Eating Habits of Cats
In nature, cats are known to hunt smaller prey multiple times a day. Research by Fitzgerald and Turner (2000) indicated that cats kill an average of 12 small animals (mainly rodents) to meet their daily energy and nutritional needs. This instinctive behavior, likely inherited from their ancestors, helps explain the frequent small meal habits of today’s domestic cats (Bradshaw and Thorne, 1992). In contrast, dogs tend to consume large meals and often use these opportunities as social periods, akin to humans. Cats are strict carnivores, with diets primarily consisting of muscle and organ meats from other animals (Lei et al., 2015). Consequently, the percentage of metabolizable energy from protein and fat is very high (up to 90-95%), while the contribution of carbohydrates should not exceed 10%.
Additional factors influencing cats’ food intake preferences include odor, taste, texture, and particle size (Hullar et al., 2001; Small and Prescott, 2005).
2. Appetite Regulation
Appetite regulation in cats is primarily controlled by signals generated by the hypothalamus and peripheral organs such as adipose tissue and the digestive tract. Hormones or cytokines produced by adipose tissue, known as adipose factors, play a crucial role in regulating appetite, energy balance, and metabolism of glucose and lipids (Zoran, 2010). Leptin, a protein hormone secreted by adipose tissue, has been shown to reduce appetite and is often referred to as the “fat hormone” of cats (Appleton et al., 2000; Shibata et al., 2003). Higher body fat levels correlate with higher plasma leptin concentrations (Appleton et al., 2000).
Leptin acts as a negative feedback mechanism to limit food intake and help reduce further fat accumulation in the body. Consequently, circulating leptin levels are positively correlated with body fat levels in cats (Hoenig and Ferguson, 2002). Leptin receptors are widely distributed throughout the body, with a significant presence in the hypothalamus, the satiety center.
When leptin binds to receptors in the hypothalamus, it triggers the release of neurotransmitters that either stimulate anorexigenic neurons or inhibit orexigenic neurons. Thus, leptin plays a key role in reducing appetite and controlling food intake in cats (Appleton et al., 2000; Coppari et al., 2005). Adiponectin, another cytokine in cats, also regulates food consumption and has recently been identified as a target molecule for treating obesity and diabetes in cats (Ishioka et al., 2009). Studies have shown that obese cats have lower plasma adiponectin concentrations compared to non-obese cats, and weight loss leads to significant increases in adiponectin levels (Tvarivitaviute et al., 2012). While there is evidence that adiponectin is involved in fat accumulation, its role in food intake or appetite requires further investigation, especially in obese cats with increased appetite.
3. Sense of Taste in Cats
The sense of taste in cats helps them assess the nutritional content of their food and avoid toxic, harmful, or indigestible substances. Taste buds, the chemical sensors responding to various chemicals, are located on the tongue, palate, pharynx, and larynx of cats (Shin et al., 1995). Cats have about 470 taste buds, significantly fewer than dogs (1,700), cows (20,000), and humans (10,000) (Davis et al., 1979; Ganchiro and Ganchiro, 1987; Robinson and Winkles, 1990). Consequently, cats have a weaker sense of taste compared to many other animals. Taste buds can detect five basic tastes: salty, sour, bitter, sweet, and umami (Li, 2013).
Unlike most mammals, cats lack sweet taste receptors and show no preference for sweet compounds such as sucrose, glucose, and fructose (Li et al., 2005). This is due to the loss of the sweet taste receptor Tas1r gene. Additionally, cats reject non-nutritive sweeteners like saccharin and sodium cyclamate (Bartoshuk et al., 1975). Domestic cats possess at least seven functional bitter taste receptors but tend to reject bitter foods, unlike dogs and most other mammals (Sandau et al., 2015). Electrophysiological recordings show that water is not tasteless to cats.
Cats rely on other complementary senses to perceive food taste due to their few taste buds. Among these, smell is the most critical sense. Cats have a sense of smell 14 times better than that of humans, attributed to having twice as many receptors in their nasal epithelial cells (Padara and Jacob, 2014). Additionally, cats possess a vomeronasal organ (Jacobson’s organ) at the roof of their mouth, connecting the nose and mouth via a duct (Chung et al., 2018; Salazar et al., 1995). This organ compensates for their low taste detection ability.
When cats smell food, they open their mouths, lower their chins, bend their noses, and use the vomeronasal organ to transfer odor molecules to the taste buds on their tongues. The vomeronasal organ also determines pheromones, playing a significant role in cats’ sexual behavior (Papes et al., 2010).
4. Behavioral Responses to Different Tastes in Cats
Cats exhibit various behaviors in response to different tastes. For food with good palatability, cats show enjoyment, half-closed eyes, and prolonged behaviors such as scratching the food, licking their noses, protruding their tongues, and licking their lips. Some cats like new food, while others may refuse it due to their defensive strategy.
5. Age of Cat
Aging can decrease the sense of smell in cats. To promote eating, owners can soak dry food in warm water or feed fresh food frequently. Cats prefer wet food due to its higher water content, closer to meat. Enhancing the palatability of cat food can involve using pork liver or polyphosphates.
The taste buds of cats are innervated by four different cranial nerves in the mouth (Oliveira et al., 2016). Facial nerve receptors respond to taste agents like amino acids, nucleotides, and sugars, leading to positive or negative responses in the cat’s central nervous system. Cats respond positively to amino acids such as proline, cysteine, ornithine, lysine, histidine, and alanine, which contribute to sweet taste perception in humans (Bradshaw et al., 1996). In contrast, bitter amino acids like arginine, isoleucine, phenylalanine, and tryptophan are widely rejected by cats (Oliveira et al., 2016; Zaghini and Biagi, 2005). However, leucine, which tastes bitter to humans, is positively perceived by cats (Beauchamp et al., 1977).
Cats are morphologically and physiologically insensitive to sugars compared to ruminants and most other herbivores (Bradshaw, 2006; Li et al., 2006). They do not favor salty foods like most mammals. Alegria-Moran et al. (2019) reported that mineral composition, including ash and calcium, negatively impacted cats’ food preferences based on a 10-year food preference study.
Cats prefer acidic foods with pH levels between 4.5 and 5.5.
