Chapter 7 Feline Ingestive Behavior
The neonate generally initiates ingestive behavior within an hour after birth, usually after the completion of parturition. As maturation of the kitten progresses, numerous modifications are made in the behaviors associated with eating.
During the first 3 weeks of life, feeding sessions are initiated primarily by the queen. She arouses the usually sleeping kittens by her movements and licking and positions herself around the young, almost enclosing them with her limbs and ventrum. The rooting reflex causes the kitten to burrow into a warm object, usually its queen or littermates, and may be present up to 11 days (see Figure 2-9). Maturation of the senses, particularly vision, and of homeostatic mechanisms alters all neonatal reflexes. During the appetitive searching component of nursing behavior, the kitten’s movements toward the queen are awkward, but they become progressively more coordinated as the kitten’s muscular and nervous system control increases with age. Communal nests allow some queens to actually have nursing coalitions.124
The sucking reflex is present at birth and can be tactually stimulated over a large perioral area.117 Such stimulation results in a head turn in the direction of the stimulus and accompanying sucking movements (see Figure 2-10). Small objects in the mouth also stimulate the reflex, which is strongest immediately after awakening. Within a few days, the sucking reflex is limited to lip contact, and foreign objects in the mouth are rejected.117 That is probably when olfactory cues become more important in teat location than trial and error, the initial method the kitten uses. Destruction of the olfactory bulbs produces kittens that cannot initiate sucking even with previous experience, but it does not interfere with their ability to learn how to suck from a bottle.110 This is also consistent with the finding that odor cues may be important to locate the mother, and tactile cues help locate the nipple.118 The sucking reflex normally disappears by 23 days.108,110 Taste and texture can be discriminated shortly after birth but are apparently of minor significance in normal sucking.153
The kitten’s initial contact with the teat results in a withdrawal motion of the head, followed by a downward motion and perhaps another withdrawal before the teat is finally enclosed by the mouth. This random head bob decreases as the kitten’s ability to discriminate the teat increases. By 4 days, kittens are relatively proficient at suckling the queen, and by 1 week, little nuzzling is necessary.
Before the end of the third day and sometimes as early as the first, a form of teat preference develops, which may become very rigid. Rear nipples are used preferentially.52 In large litters there is an initial competitive scrambling and pushing, which decrease as the preference for specific teats develops. As many as 80% of the individuals nurse only from a specific nipple.61,160,166 When preferences are more loosely defined, a kitten nurses from a pair of teats, usually near each other, or from a general region of the mammary surface.160,161 Occasionally individuals do not develop any preference and will nurse randomly instead.159,166,167 The incidence of teat preference is independent of litter size.160 Development of teat preference may serve to minimize claw injuries among littermates, provide optimal stimulation to ensure milk production, and allow more rapid completion of nursing. Variability has developed with domestication because the behavior has not been considered in selective breeding.
If a specific teat is not sucked for about 3 days, milk production by that mammary gland stops.65 The appearance of the mammary region of a nursing queen makes it obvious that only certain nipples are used.
Nursing positions are identified by olfactory means, and kittens seldom nurse strange teats after the first few days if normal nursing is allowed.62,71 A kitten that takes the wrong nipple may leave it immediately or may continue to suckle until the rightful “owner” nuzzles at it. Only when nursing the preferred teat will a kitten tenaciously cling to it when challenged.160 Unlike pigs, kittens nursing from the cranially positioned teats do not necessarily become larger than their other littermates.61 Teat positions are maintained for approximately 1 month, at which time the preference becomes less rigid. At about the same time, kittens show less discrimination in nursing foster queens.62,64 In cat colonies where multiple litters are housed together, kittens commonly suckle queens indiscriminately, with little or no teat preference development. When bottle feeding is necessary, repeated use of the same bottle and nipple and avoidance of noxious or unfamiliar odors on human hands are desirable.
The “milk tread,” usually considered a part of the nursing behavior of kittens, consists of rhythmic alternate movements of the forepaws against the mammary gland. Initially, a somewhat similar pattern is observed as the neonate tries to steady its suckling position. Functionally the milk tread may serve to push the queen’s skin away from the neonate’s nose but soon becomes more important to help stimulate milk flow.52,63,64 The behavior is primarily used when milk is not coming as fast as the kitten can drink and is usually alternated with nonrhythmic sucking.
The neonate initially spends a great deal of time nursing. Each session may last up to 45 minutes, totaling about 8 hours per day.13,52,162 This amount of nursing allows most kittens to double their birth weight in 1 week, triple it in the second week, and quadruple it by the end of the third week.13,183 Milk production does increase for large litters but not in direct proportion to litter size.52 In addition, there is as much as a tenfold increase in subcutaneous body fat for insulation to aid in homeostasis.183 The mean growth rate for the first 8 weeks is 7.3 g/day (kittens from litters of seven to eight) to 13.7 g/day (kittens from litters of two).52
During the second phase of nursing behavior, suckling is initiated about equally by the queen and the kittens. At first, 40% of the feedings are kitten initiated, with marked increases later.159 By 4 weeks, approximately half of the contacts are initiated by the kittens and half by the queen.52 The intermediate phase generally lasts from the second or third week of life to the end of the fourth or fifth week, when development of vision, use of visual cues, and coordination of motor skills allow the kittens to actively approach the queen even when she is not in the nest area. She in turn lies in lateral recumbency to present the mammary region for the young to nurse (see Figure 6-9). Toward the end of this phase the kittens may initiate sucking with the female in a standing position, but she will then respond by lying down.
Near the end of the first month, kittens are very active in initiating nursing and the queen becomes increasingly evasive of them—the avoidance phase. By 8 weeks, only 5% of the contacts are initiated by the queen, 42% by the kittens, and 42% mutually.52 The increasing demand for milk at this time already has the mother eating twice what she normally would to keep up.128 At first the female avoids some of the advances of the young by jumping onto objects they cannot reach, but as the kittens’ motor skills develop, they become increasingly difficult to avoid. Avoidance is made even more difficult because their efforts are usually individualized rather than coordinated. Her tactics will change to making nursing progressively more difficult. The queen may lie in sternal recumbency to prevent access to the teats, and if the kittens become too persistent, she bats at them or gets up and moves away. When she does allow nursing, the queen is usually sitting or standing, with the kittens contorted into several postures. If she has only one kitten in the litter, she may not show this avoidance phase.
Weaning is a gradual, variable process that results from inaccessibility of the queen and increasing ability of the kittens to hunt. In the wild, cats do not wean their young, but if the queen is still lactating, the milk is of little nutritional value after 12 weeks.35,169 When this decreased value is coupled with normal dispersion necessary to obtain prey, weaning simply happens. Even without increased avoidance by the female, there is a natural tendency for the young to decrease their nursing at about the time of normal weaning.79 When kittens are confined with the queen or have ready access to her, nursing may continue for several months, although 8 to 10 weeks is most common.71,109,160 There is an inverse correlation between litter size and length of time the female allows nursing.13 Smaller litters nurse longer. Kittens born in the spring often continue to nurse for 3 to 5 months, until fall.95,185 Some queens will let a kitten nurse until just before the birth of her next litter, as much as a year later, then aggressively chase it away. The older offspring may return shortly after she queens and continue nursing, lying among the neonates.
The transitional stage of ingestive behavior occurs while the kitten is both nursing and eating solid food. Starting near the end of the fourth week of age, this mixed nutritional period lasts until the kitten is normally weaned, at about 8 weeks. Domestic kittens begin eating solid food between 28 and 50 days of age (mean 32 days), often by following the queen to the food bowl or accidentally stepping in the food.17,160,169 Immediately preceding the transition to solid food, kittens may be noticed to eat dirt or litter.
If the queen is a hunter, she introduces her young to solid food in the form of small, dead prey. Around 35 days, she eats it in their presence, but by 6 weeks some of the kittens start eating with her on their own. That ensures that solid food will be available to the young when they are ready. The queen apparently brings prey to the nest in response to the characteristics of kittens of an appropriate age, because a nonlactating queen may bring prey to another queen’s kittens of the appropriate age.13,63
Felis catus has been described as the most perfect carnivore, because its entire body is geared to predatory life. In addition to sensory and locomotor adaptations, the cat has laterally flattened canine teeth, which permit it to sever the spinal cord of its prey without damaging the vertebral bodies. The lever action of the jaw and the scissor action of the premolars also hasten the killing and eating of prey because no molar grinding action is necessary. Thus the cat has rudimentary molars and almost no lateral jaw motion. The cat eats from the side of its mouth, using the premolars to tear flesh, rather than from the front like a grazing animal. While the cat is chewing, the ear and vibrissae on the side of the prey are noticeably flattened to the head.75 Sharpened claws on the thoracic limbs aid in catching prey, and their retractability by means of specialized ligaments helps maintain their extreme sharpness. Padded feet allow attack by ambush, and the shortened alimentary canal permits rapid digestion so the cat does not have to carry excess weight.
Farm cats are considered primarily hunters, although in fact much of their diet is supplemented by humans. They will spend 3.9% to 25.7% of their time hunting, usually around noon and dusk, and 1.2% to 3.4% feeding.146 Approximately 36% of cat owners report having seen their cats with prey.157
Rudimentary predatory behaviors can be seen at 3 weeks of age.143 Then, prey recognition begins toward the end of the first month, when the queen brings home dead prey for her offspring to smell and eventually taste. In another 3 or 4 weeks, the queen brings weak or wounded prey so the young can begin acquiring their own hunting skills. For each of these behaviors, the queen’s own prey-killing and eating instinct must be inhibited, primarily in response to kitten-related cues. Kittens will interact with prey more quickly and for longer periods immediately after the mother’s bout.39 Between 4.5 and 7 weeks, most predatory behaviors are significantly correlated with each other.
Hunting techniques are developed by practice during play and during prey sessions with the queen. The chase and catch aspects of hunting are thought to be innate, but manipulative and positive contact responses are acquired behaviors.13,72,158 The chasing, catching, and killing aspects of hunting may also be learned or at least perfected by learning. The nape bite is the prey-killing behavior that does not usually appear in play and must be perfected with practice on actual prey. When the kitten’s hunting style fails and the mouse or other prey escapes, the kitten is given another opportunity because the queen recaptures the mouse and drags it back to the young. Kittens follow the queen on hunting trips to perfect their skills as they approach self-sufficiency. By 15 to 18 weeks, exploration and hunting take up to 68% of the young cat’s time.182
Predatory tendencies are inherited and have probably been modified by domestication, making prey-killing cats generally less defensive and more aggressive than nonhunters.1 These tendencies are influenced by early experience. Competency in predation is related to the presence of the queen during the kitten’s exposure to prey and to experience as an adult.23,37,38,87 Kittens hunt the same prey they observed their mother kill and bring home. Cats are better able to catch prey if they had experience with prey by approaching, manipulating, and biting them in a play context as kittens.36 Learning to kill prey is generally limited from the sixth to approximately the twentieth week, but for the few cats that learn after that age, the process appears almost laborious.123 If the young never observe this process, approximately half will learn hunting skills on their own. Even if a kitten is never exposed to hunting, at an appropriate age the cat responds to the squeak of a mouse by attacking it.74 The way a kitten is raised will also be important in future hunting behavior. A young kitten raised only with a mouse or rat seldom becomes a hunter, but the approximately 17% that become hunters do not generally hunt the type of prey with which they were raised. If the kitten is raised with a mouse or rat in addition to other kittens, socialization to the natural prey is minimal.111,112
Although rustlings or squeaking may initially attract the cat’s attention, the sight of moving prey is the primary factor initiating hunting behavior. With experience a cat can learn to recognize immobile prey.176 Kittens can visually orient to prey as early as 9 days of age.158 Hunger and prey killing are independent, but the former can lower the threshold for the latter.20,122,138 After being alerted to potential prey, even prey as large as itself, a cat approaches the prey in a stalking ambush. Initially the cat will head to a particular area, and when it arrives, the gait changes to a slow walk as it looks over the area.176 Once prey has been spotted, the cat crouches close to the ground and uses a slinking trot, stopping periodically behind cover. It lies there temporarily with forelimbs under and elbows protruding. The entire pes is on the ground under the cat. The head is stretched forward, as are the ears. Whiskers are spread. As its eyes follow the prey, the cat usually twitches its tail.13 The stalking continues periodically until the cat nears striking range. At that time it again stops and lowers its body, proceeding at a cautious, low-profile walk (Figure 7-1). At the last available cover, there is a final pause during which its tail twitches with great intensity and the caudally positioned pelvic limbs tread, swinging its entire hindquarters to and fro.13 Then, after a short run, if necessary, the cat springs forward to seize the prey. In this pouncing attack, its pelvic limbs usually remain on the ground and only its forefeet are used in the capture (Figure 7-2). As soon as its forelimbs leave the ground, its rear limbs spread apart to stabilize the cat and help it brake. In this way, the cat can change direction to accommodate zigzags made by the fleeing prey. If instead both thoracic and pelvic limbs were off the ground during the lunge, the cat would be committed in its direction of travel. The cat that misses its intended prey makes no attempt to correct the error. Instead it temporarily withdraws, and if conditions are still favorable, it renews its attack.123 On average, a cat will make 3.6 pounces for each vertebrate it catches while hunting.146 Cats have been known to leave one mouse in favor of another more active one.13
Captured prey are restrained and positioned for the kill with the forepaws and killed by the nape bite. The accomplished hunter aims this bite at the dorsal aspect of the neck, directing its canine teeth between adjacent cervical vertebrae to sever the spinal cord or into the atlantooccipital joint to pierce the medulla oblongata.107,123 The innate directing force is governed visually by the constriction of the prey’s neck and tactually by the direction of the prey’s hair. The canine teeth of F. catus are flattened laterally so that they serve as a wedge.64,123 In addition, there are numerous nerve receptors at the base of these teeth, probably to help direct the killing bite. Rapid contraction time for the muscles of mastication permits a rapid bite after correct placing is achieved.64,72 A young inexperienced kitten, especially a timid one, may not initially use enough strength to kill the prey, but competition with littermates and repeated attacks increase the excitement until it eventually makes the kill. A few kittens never reach that point, and for older cats the necessary amount of excitement is very difficult to achieve. After a few successful kills, kittens appear to become less skillful as they individualize and perfect their techniques in more difficult situations, such as when the mouse is not running directly away. This may be a time when perfecting certain skills or the reorganization of the hunting behaviors means too much concentration goes to certain aspects at this time.40 Killing of prey is related to size and hunger. The probability of a kill increases with hunger and decreases with larger prey size.20 When these factors are in conflict, the cat is more apt to play with the prey first.20 Diazepam used experimentally on cats that would immediately kill prey caused them to show prey play first.116
The learning process associated with the nape bite involves several interesting features. On occasions when the bite is not directed correctly, the kitten may secure another portion of the prey’s body. The prey may turn around and bite the kitten’s nose.13 The initial kill is usually unexpected by the kitten, and it tries to continue playing with the now motionless prey. The kitten must make several kills before it associates the neck bite with its ability to transform live prey into food, and only then does hunger initiate prey-catching actions.13,63,123 If the prey is killed by a method other than the nape bite, the cat may perform a nape bite on the dead animal, usually before eating it but occasionally after the initial stages of ingestion.123 When not used for awhile, the skills associated with killing tend to atrophy.123
Eating killed prey is another behavior based on experience. If the kitten learns to eat dead prey from the queen, it will eat the prey it catches. The kitten that has eaten raw meat but not fresh prey will eat the prey it catches if the prey is cut open to release the smell of fresh tissue or if it accidentally draws blood or tears muscle during the kill. Cats raised as vegetarians will kill but usually do not eat the prey.13
After the kill, a cat will often groom itself and then take its dead prey to a quiet area before eating it. Farm cats will often bring prey back to their kittens, and owned cats bring it back to their owners.95 When eating a mouse, even a young cat will begin with the head and work caudally while crouching over it. This orientation is tactile, based on the lie of the prey’s hair. Some cats may try to bite the abdomen first but soon move to the head. Usually the entire animal is consumed, with the occasional exception of the tail.
Catching, killing, and eating prey are behaviors along a continuous gradient of activation.152 Each has its own threshold level for performance. To get close enough to kill some mice, a cat must attempt to catch more than it can eat. Some mice escape, perhaps two of three.121 A cat that is introduced to a limitless number of mice one at a time will first catch, kill, and eat the prey. In time, the animal will catch and kill but not eat the mice. With continued introduction of mice, the cat catches them but does not kill or eat. Finally, with physical fatigue, the mice are ignored.181 Cats will catch an average of 15 mice per test.136 Thus hunger and feeding are not necessary to maintain rodent killing by an experienced hunter.138,154 They may serve as potentiators of hunting, particularly in naive cats.154 Body condition and diet also do not influence the frequency of hunting.157
The environment probably necessitated that early felids use high-search, low-pursuit hunting techniques. Because of this evolutionary development, and because the prey is small, cats usually are solitary hunters. On occasion, two and three individuals hunt within 50 to 75 yards of each other; however, true cooperative hunting is rare and mainly restricted to courting pairs.57,113
As a means of rodent control, the cat is unsurpassed. Although cats are important in this control, the emigration of cats into an area without resident cats will lag the increase in the rodent populations.150,151 Cats cannot depopulate an area of rodents completely, but they can prevent a population increase.124 Other control methods depopulate a specific area only, but spaces within 50 yards of homes with hunting cats do not become reinfested.59,122 In a study of recently killed, untamed cats, mice and small rats were proven the major type of food.148 Most had 1 or 2 mice in their stomachs, but one animal had 12.176 Seldom has a cat been seen catching more than four vertebrates per day.146 Records that have been kept concerning ingestion of rodents show one cat killed 22,000 mice in 23 years, and another, younger than 6 months old at the time, killed 400 rats in 4 weeks.186
Studies of ingested material in feral cat populations confirm that mice are the cat’s primary food. Other prey varies seasonally but includes voles, bats, small reptiles, carrion, rabbits, birds, and insects. Rats weighing less than 200 g are another prey species, but half are killed and not eaten.45 Feral cats tend to be opportunists and scavengers, so the type of prey is largely dependent on its relative abundance.49 The availability of commercial food or table scraps does not decrease consumption of wild prey.51,81
Birds do not make up as much of the cat’s diet as is commonly believed, with human activity being 56 times more likely to kill birds than cats.148,149 Spring and summer hatches provide most of the supply, and cats that hunt near roads apparently kill more birds than those hunting in fields.58,132 Most garden-type birds tend to breed at the edges of woods and in clearings where they would be preyed upon by several species of animals, not just cats.133 Special hunting skills are required to catch flying prey, so not all cats are successful. The best hunters attack as soon as they spot the bird because ambush techniques often send the intended prey hopping or flying. The bird is usually caught with one or both forepaws and instantly brought to the mouth for the nape bite. If the bird is long necked, the nape bite may be directed close to the head or the shoulder. Instinctively, the latter is more commonly used because the size disparity is greater between body and neck than between head and neck. The best hunters do not release the catch for a better neck bite, because the bird tends to escape. Except for a few feathers, which may be plucked, the entire animal is usually eaten, beginning with the head.13,28
Once a cat starts hunting birds, it is almost impossible to prevent its continuation. At best, throwing things at the cat causes it to hunt on the sly. To avoid a bird-catching cat, a kitten should be selected whose mother does not hunt birds, or it should be adopted at about 6 weeks of age. In both cases, the kitten should be confined and not allowed exposure to birds, at least until after it is a year old.27,84 Placing a bell on the cat may give birds enough of a warning.27
Rabbits caught are usually juveniles, probably because full-grown ones are too powerful.176 Even then, the difficulty of the catch of such a large animal is still greater than that of other species.176
Another less common prey for the cat is the fish. Although most cats leave fish alone, a few are noted for pursuit of the family’s goldfish. The fishing cat of Malaysia is very adept at hooking fish with its forepaws, as are certain individuals living in coastal regions or near lakes and streams. Fishing is one of the earliest skills for which selection was made in domestication. Like good bird hunters, good fishers do not let the catch go to obtain a better neck bite, because that leads to the fish’s escape. Cats having no early fishing experience may actually run away from a fish flopping along a shore.
In certain parts of the world, livestock injuries from vampire bats can be significantly reduced by hunting cats.54 Successful catches tend to occur when the bat is distracted during its hunting approach, while defending itself from the cattle, or when weighed down after feeding.
Cats continue to grow for several months after weaning. For the first 8 weeks, both sexes grow at an approximately equal rate.52 After that, males grow faster. Females grow until about 6 months of age, and males do until 9 to 12 months.168 A newborn needs 380 kcal/kg daily intake, and the requirements gradually decrease to a daily need of 80 kcal/kg in the adult.168 The average mouse meal will supply approximately 30 kcal of energy, so most cats require approximately 10 mice per day.174 Each mouse consists of 64% to 76% water, 14% to 18% protein, 6% to 18% fat, and 1% to 5% minerals.104 These data suggest cats evolved to eat several small meals a day. The immediate ancestors of the cat also ate small prey, as frequent small meals, rather than following the “feast or famine” principle typical of their large feline cousins. If allowed to set their own schedule, domestic cats will eat 9 to 16 small, evenly sized meals a day.* When fed periodically, cats tend to be more aggressive and less cooperative than if fed by free choice.66 Meal-fed cats also tend to eat and drink less often, and their urine pH, magnesium, and phosphorous levels fluctuated much more than for cats fed by free choice.66
If the opportunity exists, a great deal of time may be spent hunting. Females spend 26% to 46% of the day hunting, compared with 5% to 34% spent by males, during bouts averaging 30 minutes (range 5 to 133 minutes).176 As little as 1% of the waking time may be spent eating.85 Males generally eat more, but females show more variation in body weight, primarily because of changes in eating and activity patterns related to estrous cycles. Based on high-protein body needs, a domestic cat consumes approximately 75 g of dry food or 250 g of canned food each day (each about 250 calories) or about 30 kg of dry or 90 kg of canned food per year.47,147 Caloric intake fluctuates somewhat on a 4-month cycle along with the cyclic changes in body weight, food intake, and thyroid activity.94,100,155
Regulation of ingestive behavior is not completely understood. Several theories have been advanced but each has exceptions, so feeding may really be regulated by multiple factors. Environmental factors like availability and nutritional properties of the diet are major determinants of the eating pattern.103 As caloric density decreases, cats maintain intake based on bulk, not calorie content.103 Adult cats will also regulate intake to some extent on dry matter content. As moisture is added, consumption increases in proportion to the amount of water added.41 As the energy and safety costs of getting food increase for a cat, the frequency of eating is reduced, and there is a compensatory increase in amount eaten per meal.103,105 Theories on regulators of intake include palatability of food, blood levels of amino acids, and hepatic glucoreceptors.100, 163. There is no correlation of meal size and intermeal intervals,105 and a ration is not selected because it is nutritionally balanced.89
Ingestive behaviors of adult cats before and after feeding have been well characterized.30 Premeal behaviors are directed at the owner as both vocalization and directed behaviors. A cat will approach with its tail up and flicking as if to another cat. It will also rub on the owner and other objects. Postmeal behaviors are centered primarily on grooming, with much less owner interaction. As the cat starts to walk away, three fourths of the time the tail is lowered. Grooming begins with it licking its lips and progresses to body grooming with a licked “washcloth” paw. Before leaving, the cat performs some additional lip licking or head shaking.
Protocol when more than one cat approaches a food bowl is not governed by social status as in other species. Instead, cats usually adhere to the first-come, first-served principle, or they may share. Because cats do not know how to behave toward each other when eating together, the individual arriving later may choose to wait. Who eats first or how many eat at the same time depends on individuals rather than on age, sex, or other dominance factors (see Figure 4-4). One cat will occasionally take prey from another, particularly if there is a distraction.
Initial gustatory responses appear as early as the first day of life and basically involve differentiation of salty milk from regular milk.50 By 10 days, responses are also seen to bitter, sweet, and sour.50,178 Maturation involves changes in ingestive behavior, but environment is probably the strongest influence on food preferences. The specific prey introduced by the queen or food type fed by owners to the juvenile often determines the patterns in the adult, with food preferences generally established before 6 months of age. If the kitten was not exposed to a variety of food flavors and textures, food preferences can be so limited that the cat may even refuse to eat anything except its one or two choices. Cats tend to be extremely particular, and the assumption that the cat will eventually eat a nutritious food when it becomes hungry is not correct. They have been known to refuse a nutritionally complete, unpalatable diet for a prolonged period,104 and they literally starve to death rather than eat an unacceptable meal. Queens have been known to eat their young while in this state, never touching the available food.14
Preferences can be shown behaviorally. The introduction to a food that produces a “lick/sniff food, lip lick, and groom face” response indicates it is a desirable meal.177 A “lick/sniff food and lick nose” shows a degree of undesirability.177 Whether the aversive food is eaten then depends to some degree on hunger. Cats that are used to a variety usually will prefer a novel diet to their regular one.31,46,89,94 This preference is short lived, however, if the new diet is less palatable. Preferences can also change significantly over time. For cats that are not used to variety, foods should be changed gradually by mixing well 20% to 25% of the new food with the old. This first mixture should be offered until it is readily accepted, which usually takes up to 14 days. Then the mixture may be further changed by introducing another 20% to 25% of the new food. These steps should be repeated until the new diet is being fed exclusively.
Initial selection of a free-choice food depends on odor, which can provide the sole basis for dietary selection.28,139 If the smell is acceptable, the front of the tongue brings in the next information. Undesirable odors, tastes, or textures can overrule the metabolic need for nutrition and are more important as negative factors than positive ones.48 That explains why some cats will eat a novel diet if it is aesthetically acceptable.85 It is related to the relatively rapid acceptance of most new foods. Rejection can also occur after a period without a particular type of food.29 Meat is obviously the food of choice, and older cats prefer kidney.28,178 They also choose fish and commercial cat food over rats.94,99 Cold, dead rats are slightly more palatable than the fresh kill.99 Ranked in decreasing order of general feline preference is flesh from sheep, cattle, horses, pigs, chicken, and fish. Whether a meat is raw or cooked is relatively unimportant; however, foods at body temperature are preferable to those at higher or lower temperatures.28,139,178 Moisture, which may help release odors, enhances palatability, and spicy foods are usually disliked.28,178
The physical features of a food are involved in food selection. Cats prefer solutions with a greater density (whole versus diluted milk) but are more cautious with doughy textures.104 As a diet becomes drier and more powdery, acceptance also decreases.104 Fats are desirable, with tallow preferred over chicken or butter fat, and these are preferred over corn oil.104
Some flavors are selected against by cats. These include saccharin, cyclamate, casein, medium-chain triglycerides, caprylic acid, and certain combinations.12,104,125 Studies conflict over a cat’s ability to detect sweets.11,12,104 That may be why sucrose does not increase palatability in cats as it does in other species.94,100 Cats do like sweet solids like ice cream, so one could say they really find the combination of sweet, fatty, and milky texture highly palatable.94
Individuals can have strong preferences that are unique from other cats.89 One cat, raised by a Jewish rabbi, observed Jewish laws by not drinking milk when eating meat, even though both were available. This illustrates that variations do occur based on individual factors and environmental influences.114
Prey preference can exist not only in hunting but also in consumption. Mousers generally catch all kinds of mice but refuse to eat certain types of mice, birds, moles, and shrews. Snakes, frogs, and toads are rarely eaten, although they may be hunted and caught.13
Food preferences are not restricted to meat, and that may again reflect the wild heritage. Grass and other vegetable matter can be found in the feces or stomachs of approximately one third of feral cats. Animals serving as normal prey for F. catus are primarily vegetarians, so when the prey is eaten, vegetable matter becomes part of the cat’s diet. Therefore most of the vegetative matter consumed has already been partially processed by the prey’s intestinal tract. Although cats can digest a small amount of fresh vegetable starch, large amounts of uncooked carbohydrate may cause vomiting or diarrhea. Because cats lack the ability to break down the beta bonds of cellulose to glucose, fresh grass remains unchanged within the gastrointestinal system and may actually become irritative.15 Because the indoor cat is most apt to consume large quantities infrequently, grass has commonly been assigned the role of a purgative for such things as hair balls. If, however, the cat is introduced to small portions of vegetable matter early in life, it can be somewhat omnivorous. Eating grass for gastric distress may be a learned behavior, in the tradition of other species that learn self-medication.94 Garbage is also commonly eaten, representing an opportunistic adaptation.68
Around the fifth week of life a young kitten begins drinking from dishes. By adulthood the average cat requires approximately 44 to 66 ml of water per kilogram of body weight per day.168 Kittens need 66 to 88 ml/kg/day.168 Water is available to an animal from three sources: drinking water, water in food, and water from nutrient metabolism of fat and energy.165 A canned food diet is 74% water, making 49.8 g/kg available to the adult cat from the diet. It would supplement its intake by drinking 7.3 g/kg.168 This means for the average cat, approximately 185 ml is available directly. About 15 ml more comes from fat metabolism. The cat may not need to drink. Dry food has only 10% water, thus supplying 7.5 ml, with another 7.5 ml available from fat metabolism.47 In this case 185 ml of water must be ingested directly.
A kitten learns to drink by first lowering its head until the mouth touches the water. The head is then raised, and water is licked from around the mouth. The adult cat usually crouches over the water source and uses its tongue to bring water into its mouth (Figure 7-3). For this, the tip of the tongue is curled caudally, forming a ladle to lift the liquid into the mouth, and the cat usually laps four or five times before swallowing.13 Occasionally house cats prefer to drink from the toilet bowl or a drippy faucet (Figure 7-4). Generally one of two postures is used. If possible, the cat prefers to keep both hindfeet on the floor, leaning or stretching as necessary to lap the water. If this is impossible, the cat will straddle the toilet or sink, bracing itself while it drinks. More than one cat has lost its balance, and some will then no longer use that water source.