Factors Affecting the Feeding Behavior of the Cat

Feeding behavior corresponds to all the motor sequences from the search for food, its recognition, acceptance and intake. It thus begins with exploration and ends with swallowing.

Although feeding behavior is well studied in domestication and production, only empirical data or anthropomorphic analysis is available for cats. Some recent scientific experiments, essentially performed by petfood manufacturers, are completing the scope of data available in pets.

The feeding and social behavior of cats differs greatly from dogs. Not only do their nutritional requirements differ, but the social structure of cats also results in different communication and feeding patterns both between cats and with their human caregivers. Meeting the nutritional needs of cats requires an understanding of their feeding ecology, nutritional needs and social communication and structure.

Debra HORWITZ
DVM, Dipl ACVB

Dr. Horwitz graduated from Michigan State University College of Veterinary Medicine. After several years in general practice, she began to limit her practice to behavioral problems in companion animals. She received board certification from the American College of Veterinary Behaviorists in 1996. She has a private referral practice for behavior problems in dogs and cats and also consults for the Veterinary Information Network and lectures frequently in North America and abroad and is the editor and author of several books on behavior. She is president of the American College of Veterinary Behaviorists 2006-2008.

Yannick SOULARD

An agricultural engineer with a Master’s degree in managing innovation in biotechnology and the agro-food industry, Yannick Soulard joined Royal Canin’s Canadian subsidiary in 1999 as a support technician for the sales team. He was given responsibility for formulating foods for North America until 2001. Back at the Royal Canin Research Center in Aimargues, France, he spent six years in palatability development. Today, he leads the Nutrition research unit.

Ariane JUNIEN - CASTAGNA

After graduating from Université de Technologie de Compiègne in 1996 (agro-food process engineering), Ariane joined Royal Canin in 1997, initially in production. She moved to the Research Center that same year, working on an industrial pilot. Since 2001, she has been in charge of palatability development projects.

1. Factors Affecting the Feeding Behavior of the Cat

Hereditary Determinants

Sensorial Aspects

Taste

The sensation of taste in a cat is present 5 days before birth (Beaver, 1980) and improves during life. The sensitivity differs between the 4 main types of taste perception, with the following hierarchy from the most to least stimulating (as demonstrated by the simple application of vinegar, salt, quinine, and sugar, on the tongue):

acid > bitter > salty > sweet

(Domestic cats are neither attracted to, nor show avoidance of the taste of sweet carbohydrates and high intensity sweeteners).

Our knowledge of taste has indeed evolved through the study of neurological signals in cranial nerves following the stimulation of the taste buds by different substances. Three cranial nerves are involved in taste. The facial nerves, in particular the chorda tympani, have undergone the most observations. This research has given rise to many theories. For example, Boudreau (1973,1977) presented a theory suggesting acid, amino acid and nucleotide taste systems specific to cats. This theory has not been confirmed by other authors.

The number of taste buds is estimated at around 475 (Figure 1 and Figure 2). It is much less than dogs (1700) and man (9000). In dogs, gustatory cell turnover is around 4 days. No data is available in cats, but we may expect that it is similar. This data is interesting to evaluate appetite recovery after insult to the oral epithelium.

Figure 1. Localization of the taste receptors on the tongue of the cat.

Figure 2. Different types of gustative receptors.

Bitter Taste - Bitter compounds easily trigger aversions. Bitter taste is due to a wide variety of components (tannins, alkaloids, malic acid, quinine, phytic acid, aminoacids such as tryptophan, isoleucine, leucine, arginine, phenylalanine, etc.).

Cats are very sensitive to bitter tastes (Houpt, 2005). Cats are more sensitive than dogs to bitterness and detect it at lower concentrations. They can detect concentrations of bitter taste four hundred times smaller than levels detected by hamsters (Carpenter, 1956; Houpt, 1991). This perception enables them to avoid many toxic substances (for example strychnine), which are often very bitter.

Sweet Taste - Cats do not appear to care for sweet tastes: receptors have been deactivated. The corresponding gene exists but it has been switched off to a pseudogene (Brandt, 2006) through phylogenic adaptation (Li et al, 2006). Cats tend to reject synthetic sweeteners like saccharine or cyclamate, since they are perceived as bitter (Bartoshuk et al, 1975). The sweet taste of antifreeze appeals to dogs but not to cats. Rather, cats are typically poisoned by cleaning their paws after walking through the antifreeze.

Acid Taste - This perceptiveness is widely used by petfood companies. Many commercially available cat food flavors indeed contain phosphoric acid. Excessive acid and phosphorus intakes must be avoided in cats with impaired renal function.

Salty Taste - The perception is rather positive in cats and can enhance food or water consumption. Some water taste was hypothesized in early experiments, as taste receptors were thought to be reacting to distillated water. However, these electrophysiological responses were in fact the result of the adaptative neutrality of the cat’s taste receptors to saline saliva.

Amino-acids - The taste buds connected to the facial nerve are highly sensitive to amino-acids: a single amino acid is able to stimulate the taste nerve fibers. These changes appear to be a specialization for feeding on prey, which is rich in protein (Bradshaw et al, 1996).

Oral sensitivity is not only gustatory, but somesthesia is important for granulometry and temperature detection through the lingual nerve. The ligaments of the teeth also participate. Any paradental disease or the effect of age, through modification of the resistance of the gums and teeth can strongly modify food perception and palatability.

It has been shown that the perception of food flavor is not simply the superposition of the various taste varieties but sensory messages are creating a brain image that is compared to innate or learned schemes (Gallouin, 1987). However, no specific data exist for cats.

Olfaction

Olfaction is present at birth and matures by three weeks of age. The cat is less sensitive than the dog to smell. This difference in sensitivity is due to the number of olfactory cells, rather than their density in the mucosa. Cats have between 60 and 70 million olfactory cells (compared to 80 - 220 in dogs). In some animal studies, it has been estimated that only 1% of volatile compounds enter the nasal mucosa (Figure 3) however, no direct data exist in cats.

Figure 3. Air circulation in the nasal cavities of the cat.

The cat is very selective and cautious. Olfaction is THE key factor to trigger food acceptance. Any anosmia will prevent food intake, and this anorexia will last as long as the cat cannot smell (May, 1987). Renewal of the olfactory mucosa and appetite recovery requires four to five days.

The range of smells perceived by cats is large but some specific odors are particularly attracting for them:
- Mineral origin: bleach
- Plant origin: catnip, olive wood, valerian, asparagus, mint, papyrus, cloves, mimosa
- Animal origin: pheromones (although they do not have any direct food related meaning, but only territorial or sexual), livers, meats, viscera, etc.

However, detection ability does not mean food preference and no clear data exist on individual variability.

Some unusual odors or pheromones often trigger a specific reaction, called the Flehmen reaction, during which the cat lifts its upper lip and breathes some air through the vomero-nasal organ (Jacobson organ) located in the hard palate.

Petfood manufacturers are of course working on volatile compounds that are able to attract both the cat (when approaching its bowl) and the owner (when opening the can or the bag of kibble). However, as can be expected, this area of research remains very confidential and unpublished.

Vision

Lott-Brown et al (1973) have shown that cats are not able to discriminate between 520 and 570 nm lengthwaves. They thus would be unable to discriminate white from yellow or green. It would be for the cat the same "tonality". Red and blue are conversely clearly differentiated. As a result, we may assume that colors of food are more important for owners than for cats.

The cat’s vision is panoramic and adapted to discriminate movements more so than tonal differences. This ability has clearly evolved to facilitate predation.

Behavioral Aspects

Pre-natal experience

The acquisition of certain preferences may occur very early in life, as early as during gestation. Fetuses are surrounded by amniotic fluid, which contains compounds they assimilate in utero (Thorne, 1994). A cat’s gustatory system is functional in the final days of gestation (Tichy, 1994).

Suckling Behavior

Thanks to a burrowing reflex which lasts until the 8th day after birth, the new born kitten chooses a nipple during the first two days of its life. This reduces competition between littermates and decreases the time to initiate suckling (Foucault, 1992). Temperature (of the skin) and olfactory stimuli (from Montgomery glands secretion around the nipples) are the most important after birth.

The suckling reflex appears from the 50th day of gestation and is gone by the 23rd day of life. (© Yves Lanceau/RC/British Shorthair).

There is nevertheless a maturation process during which regulatory factors transition from oral stimulation by milk up to the 10th day, to peri-oral stimulation (whatever the food is). The effect of digestive filling appears from 3 weeks of age.

The time allocated to suckling changes during the first month according to a relatively constant scheme. Kittens spend 10% of their time suckling and get milk for the first 2 weeks. Suckling time increases quickly up to 60% at 3 weeks and then decreases to 10% at the end of the first month (Foucault, 1992). They also spend time to suckle without drinking any liquid.

The evolution of the kitten – mother bond around food evolves quite significantly during this time. During the first two weeks, 75% of the suckling periods are initiated by the queen. During the two following weeks, the proportion falls from 50 to 5%. The mother then begins to avoid her kittens and allocates them only 20% of her time. Weaning is in fact beginning, with major behavioral and digestive changes.

During lactation, the composition of milk varies with the mother’s diet. Kittens may develop certain preferences at this time in their lives (Thorne, 1994). Few articles describe this for cats. Weaning has in fact been more throughly studied.

Weaning Experience

When eating their first solid food, kittens choose what their mothers eat, even if this food is unusual for cats (Wyrwicka & Chase, 2001). Dietary preferences are thus not all innate; they are acquired through social influences after birth.

Kittens whose mothers have been conditioned to eat bananas (usually unpalatable for cats) will eat bananas during weaning even if they have access to more conventional food for cats such as kibbles (Wyrwicka & Long, 1980). Kittens imitate their mother’s eating behavior down to the smallest detail. They begin by eating from the same plate, at precisely the same spot, as their mother takes its food. There is a correlation between the mother’s dietary consumption and that of the kittens. In the above experiment, the kittens that ate the least amount of banana were those whose mothers ate the least. The influence of the queen can last after weaning and separation between kittens and their mother. Food preferences acquired during weaning in their mother’s presence persisted in kittens until the age of 4 to 5 months (Wyrwicka & Long, 1980).

Weaning is an important time in an animal’s dietary history. The moment a cat eats its first solid food is probably crucial in terms of influence, especially if it happens in their mother’s presence. (© Yves Lanceau/RC/Egyptian Mau).

Kittens are more likely to eat a new and novel food when the queen is present than when she is absent (Bateson, 2000). The illustration of the importance of the mother in food acceptance by kittens has also been illustrated in a trial from Wyrwicka & Chase (2001). Nineteen kittens from four litters were studied. Ten kittens ate in their mother’s presence, while nine were without their mother during meals. The time it took kittens to accept a new food was very different between groups:

- For the kittens eating in their mothers’ presence, it took an average of 5 hours for them to eat a new food

- In contrast, in the kittens separated from their mothers it took 4.8 days before they would eat a new food.

Therefore many dietary habits are determined before 6 to 8 weeks of age. The practical consequence is that food education must be done at this stage. A good idea is to select, at least for the first weeks after adoption, the food used by the breeder.

Individual and Breed Differences

Kittens fed by stomach tube have very limited gustatory experience compared to kittens fed normally. During conditioning tests in which success is rewarded with food, the kittens fed by stomach tube took longer to succeed and even refused to eat the reward (Stasiak & Zernicki, 2000). Being deprived of dietary experience then influences future feeding behavior. All the early sensorial or digestive experiences create the individual variability. Learning leads to avoiding harmful or unpleasant foods and to preferably seek for nutritionally or sensorially gratifying ones.

Sex has no recognized effect on food perception in this species, even if feeding behavior can be indirectly affected by acute territorial competition in female cats, and by breeding season in male cats.

One peculiar feature in cat palatability testing that offers the choice between two bowls, is that some tasters always choose one side, regardless of the diet inside the bowl. Some cats are thus left handed, other are right handed! (© Royal Canin).

Breed may have some influence, although it is difficult to prove it unequivocally. It may be an area of future research.

Age affects ingestion behavior but less than in dogs (Peachey & Harper, 2002).The increase of dietary experience and the decline of olfactory and gustatory capabilities may enhance fussiness or even provoke preference inversion.

Environmental Factors

Social Environment

The cat is a solitary hunter, but tends to gather in feeding and breeding spots in wild urban groups. The territory is transient and variable throughout time and space, i.e., it is possible that the territory overlaps between two cats but at different moments. Hierarchy in cats depends on the place and time during the day: it is a relative dominance. Territory may easily trigger aggressiveness and fights.

Unlike dogs (Table 1), household cats do not appear to show social facilitation of eating: they usually eat alone and do not seem to be affected by the presence of another cat (Houpt, 2005). Some cats will even share the bowl with another cat, while others may sit calmly and wait for their turn. A female in estrus can have the right to get food first. However, other researchers feel that cats show hierarchical issues regarding the food bowl with higher ranking cats displacing lower ranking cats from the food source in a multi-cat home (Knowles et al, 2004). In ad libitum experimental situations, social feeding (as defined by time overlap of at least one minute between meals), occurs in duo with only 20% of meals (Mugford, 1977).

For owners of cats living outdoor, feeding is a privileged moment for contacts. Quite often, the feeder has better or, at least, the easier relationship with the cat. Geering (1989) has shown that the act of feeding is necessary to reinforce the bond, but is not sufficient to keep it. Other interactions, like petting, grooming, playing, talking, are required to maintain a newly established link (Bateson & Turner, 1989).

In collective housing, it appears that some competition may occur. Fights are somewhat rare if food is available in large quantities. (© Yves Lanceau/RC/European cats).

In the household environment, the rhythm of the supply of food often reflects the owner’s lifestyle. Two or three meals are often fed during the day: in the morning before going to work, at the evening when returning, or even just before going to bed to keep the cat quiet!

Diet acceptance is largely influenced by the psychological, affective and material environment (Figure 4). Wolter (1982) mentions various factors likely to influence the feeding behavior of the cat: tension between family members, change of light, sudden noise from stereo systems, different odors of cleaning product for the bowl, arrival of strangers, etc. This has nothing to do with food quality but an involuntary cat disturbance. Checking the feeding behavior during a recovery phase can lead to food refusal or lower acceptance. This situation is also observed when the owner has just bought a new food (new brand or new claim) and wants to check whether or not the animal accepts it. A very first analysis of perceived anorexia should review these unexpected but simple reasons! This disorder will be reviewed in the final section.

Figure 4. Factors contributing to diet acceptance.

Physical Environment

Cats need to feel safe and secure within their home environment. To this end owners need to provide facilities for the main behavioral functions of eating, sleeping and playing and also ensure that the cat has the ability to control its own stress through the natural mechanisms of hiding and retreating. In tidy homes or those with built in furniture, places for cats to hide may be in short supply. This may create a situation where a cat might feel insecure and vulnerable without any escape routes or hiding places. Taking steps to provide the cat with a constant and predictable environment, both in terms of physical structure and scent profiles, will help to increase the cat’s security; while the provision of access to high up resting platforms, secure bolt holes and hideaways may decrease the use of oral appeasing behaviors, such as over grooming and over eating. If all of the furniture in the house is built in it may be necessary to put up shelves for the cat to rest on, or clear out part of a cupboard or wardrobe to offer a safe hideout (Dehasse et al, 1993).

Influence of the Food Itself on Feeding Behavior

In the testing done on food choices and taste reactivity in cats (Van den Bos et al, 2000) two response sequences were noted and correlated to possible palatability reactions. A preference to consume an offered food was often preceded by a lick or a sniff of the feeding bowl, lip lick and face groom. Cats presented with food that was less desirable would lick or sniff the food and lick their nose. Whether the food was eaten was also partially dependent on the degree of hunger. In general cats will eat more of a desirable food regardless of hunger, but consumption of a less desirable food is often dependent on the hunger status of the cat.

Once a meal is consumed most cats will groom themselves regardless of perceived palatability. As direct gastric canulation leads to the same post-prandial behavior (without soiling lips and cheek), it is considered as an innate neurophysiologic reflex.

One of the most important features to consider is that cats will often eat and prefer a novel diet over a familiar one. The intensity of neophilic behavior depends on the foods’ relative palatability and on the duration of exposure to the usual food. If the new food is less palatable than the usual food, the effect is shortlived. Twenty four kittens received the same food for 16 weeks, and then underwent a comparative test [two bowl test] for several days with the usual food and a new food of equivalent palatability. The first day, the kittens systematically chose the new food. After the second day, the difference was no longer significant between the two foods (Mugford, 1977). The novelty effect lasted only a few days (rarely more than 5 or 6 days), after which dietary preference stabilized.

Neophilia is preference for a food never encountered by the animal or food that has not been recently encountered by the animal. This behavior is quite common in carnivores and has been identified in both dogs and cats. Neophilia enables animals to diversify their diet and achieve a better nutritional balance.

In the home, the preference for frequently changing the diet, a ritual that many owners participate in, is called metaphilia (from the greek, meta: "transformation"). This corresponds to an increase in consumption due to the renewal and alternation of known diets (Rabot, 1994). This is clearly observable in the cafeteria regimen in practice. This behavioral trait has led some manufacturers to create packaging of multi-single portions containing various varieties.

When changing a pet’s diet, one must be prepared for the possibility of neophilia and the associated increase in energy consumption during the first month after the new diet is introduced. The novelty effect is accompanied by temporary caloric overfeeding. In the first month, cats may eat up to 100 kcal/kg. The effect then wanes and consumption stabilizes around 60 kcal/kg after two months (Nguyen et al, 1999). Whenever a change is made to a pet’s diet, owners should take care to measure out the food to ensure proper caloric delivery.

Breaking this natural neophilic trend, an owner can choose to always give the same diet. There is a risk of boredom with a perceived decrease in palatability (even it the food is complete and well balanced). One may relate that phenomenon to the human concept of "oral satiation" (always eating chocolate or eating oysters too often may decrease their palatability). On the other hand, choosing to frequently vary the diets beyond the carnivorous status of cats and to consider them as omnivorous by humanization, may lead to neophobia and again food refusal.

Some specific events can trigger fixation to one food and acquired food aversion. These disorders will be discussed below.