History

Cat Feeding Behaviour and Preference

Key Message

WALTHAM has contributed to the understanding of the feeding behaviour and food preferences of the cat by:

  • Generating insights into the inherited behavioural strategies that influence when they eat, what they eat, and how much they eat.
  • In collaboration with the Monell Chemical Senses Center, identifying the molecular mechanism underlying the cat’s indifference to sweet taste.
  • Demonstrating that cats seek out particular nutrients in their food.

Background

It comes as no surprise to many owners that domestic cats are often described as finicky feeders (Bradshaw and Thorne 1992). In fact, the feeding preferences of cats are highly individual (Thorne 1994). Owners frequently report that their cat has apparently idiosyncratic food preferences, examples being particular food items or a liking for or refusal of one particular product or flavour from a commercial range.

Cats are predators and obligate carnivores, and in the wild their diet is composed of a variety of items, especially small mammals, with some birds, reptiles, insects and very little vegetable matter (Plantinga et al. 2011). Availability is undoubtedly one factor, such that the feline diet may be restricted within a locality or season. In addition, the nutrient content can differ not only between different prey species but also within a species; depending, for example, on the time of year or the age of the prey animal. Coping with a food supply that is unpredictable in terms of availability and nutrient content requires particular behavioural strategies. These have been inherited by the domestic cat from its ancestors and probably underlie much of the feeding behaviour seen today.

As in all species, taste is an important factor determining what cats like to eat. Unlike dogs (Ferrell 1984) and humans (Reed and McDaniel 2006), cats show no preference for, and indifference to, sweet compounds (such as sugars and artificial sweeteners). It seems that having evolved as an obligate carnivore the ability to taste sugar was lost and today’s cats have inherited this.

Evidence from a number of species ranging from insects to mammals (including cats) indicates that they are well adapted to dealing with a food supply of varying nutritional content by balancing their intake of macronutrients (protein, fat and carbohydrate) through adjusting their intake of different foods (Simpson and Raubenheimer 2012).The optimal macronutrient profile for the cat is one which best matches its nutritional and metabolic needs – which might be expected to vary depending on physiological state (for example growth, adult maintenance or reproduction).

Understanding the complex feeding behaviour and preferences of the cat is a challenge. Multiple factors determine when cats eat, what they eat and how much they eat – including inherited attributes, dietary nutrient content, the cat’s physiological state and the owner’s behaviour.

Why WALTHAM is Interested

To produce diets that cats like – and continue to like – requires a fundamental understanding of the basis of cat feeding behaviour and preference.

Approach

Cats have inherited feeding behavioural strategies from their ancestors and early studies were directed at gaining insight into these.

Later, molecular techniques were used to investigate the expression of the genes encoding the sweet taste receptor in the cat.

Other studies used diets with a range of macronutrient profiles and sophisticated modelling techniques to determine how the macronutrient content of the diet influences food intake.

Insight Generation (Feeding Behaviour)

Cats exhibit inherited behavioural strategies that influence when they eat, what they eat and how much they eat

Domestic cats have inherited the behavioural strategies used by their ancestors to cope with an unpredictable food supply, and these probably underlie much of the feeding behaviour seen today. Early studies at WALTHAM generated insight into these behaviours which influence when cats eat, what they eat and how much they eat.

A major factor influencing when cats eat, as well as how much they eat, is food availability. When food availability is not restricted, cats eat small, frequent meals. Studies at WALTHAM showed that if cats have constant access to an acceptable food, they take intermittent small meals throughout the 24-hour period (Bradshaw and Thorne 1992). The number and size of meals varies with the individual, generally ranging from 7–16, with around 13.3 per day (Figures 1 -2) (Mugford and Thorne 1980; Bradshaw and Thorne 1992; Mugford 1977; Thorne 1982). Restricting food availability to meal times means that the cat eats larger, less frequent meals. Cats adapt their meal size and meal frequency based on the availability of food (Bradshaw and Thorne 1992).

24 Hour meal pattern
Reproduced from Bradshaw J, Thorne C. Feeding Behaviour. In: The Waltham Book of Dog and Cat Behaviour. Editor: C Thorne. Pergamon Press, New York. 1992, Chapter 7 pages 115-129.

24 Hour meal pattern 2
Reproduced from Bradshaw J, Thorne C. Feeding Behaviour. In: The Waltham Book of Dog and Cat Behaviour. Editor: C Thorne. Pergamon Press, New York. 1992, Chapter 7 pages 115-129

Figure 1: The 24-hour meal patterning of cats given free access to a dry food (Bradshaw and Thorne 1992). Meals are taken at irregular intervals throughout the day and night. The size and frequency of meals is characteristic of the individual cat.

Other factors influencing what cats eat and how much they eat, include neophobia and monotony. These are evolutionary behavioural strategies that are common in many species. When first offered a new food, cats can be neophobic. If they are fed the same diet over a long period they may become bored (the product may be perceived as monotonous). They may then become less neophobic and seek out new food choices (neophilia). Neophobia probably safely establishes the non-toxicity or nutritional adequacy of new food items. The evolutionary basis of monotony is probably to prompt the animal to seek a varied diet to guard against the nutritional inadequacy of any one food item.

Studies show that cats exhibit neophobia when presented with new food items (Bradshaw et al. 2000). When presented with a novel food, cats eat a small amount on the first occasion before subsequently increasing their intake (Figure 3 Bradshaw 1986). Alternatively, the cat may completely reject the new food, particularly if it is very unusual, or undertake extensive sniffing first (O’Malley 1995). Neophobia is less evident in cats with a wide experience of different foods, is more evident when the cat is in a new environment and can usually be overcome by repeatedly offering the new food (O’Malley 1995).

Cats neophobia
Reprinted from Bradshaw JWS. Mere exposure reduces cats' neophobia to unfamiliar food. Animal Behaviour 1986; 34(2):613-614 with permission from Elsevier

Figure 2: Cats show neophobia on first presentation of a novel food (Bradshaw 1986). Mean percentages of flavoured food eaten on 5 test days by two groups of cats (group 2 was not tested on day 1). Food intake is low on day 1 but subsequently increases (days 8 and 9). After a 102-day break from the food, neophobia returns, with low intake on day 112

Other studies at WALTHAM showed that cats exhibit neophilia, in that when repeatedly fed the same food they seek variety in their diet. If cats are repeatedly fed a single food, its palatability transiently decreases (Mugford 1977). This monotony is evident as a gradual decline in the intake eaten at each meal (Figure 4). Subsequently, the cat exhibits neophilia, choosing alternative foods. When kittens that have been raised exclusively on one diet are offered it or an alternative, they choose the alternative (Figure 5-6) (Mugford 1977).

WDC28 feeding decline
Reproduced from O'Malley S. The role of variety in the diet. Waltham Focus 1995. 5(3):18-22

Figure 3: Repeated feeding of a single food results in a decline in intake as it becomes less preferred (diet A), which is restored upon feeding an alternative (diet B), providing it is contrasting (O’Malley 1995). Cats can show a rapid monotony response to some foods 
 
WDC49 Kittens
Reprinted from Mugford RA. External influences on feeding of carnivores. In: The Chemical Senses and Nutrition. Editors: Kare MR, Maller O. Academic Press, New York 1977, Chapter 2 P25-48

WDC49(2) Kittens
Reprinted from Mugford RA. External influences on feeding of carnivores. In: The Chemical Senses and Nutrition. Editors: Kare MR, Maller O. Academic Press, New York 1977, Chapter 2 P25-48

Figure 4: After kittens have been reared on a single canned product, they show preference for a novel alternative (Mugford 1977). In the top panel kittens maintained on liver variety cat food show a preference for the chicken variety for the first few days it is offered. In the bottom panel kittens maintained on the chicken variety cat food show an initial preference for the liver variety

These early studies revealed the complexity of cat feeding behaviour and certainly contribute to the perceived fussiness of some individuals, as described by their owner.

Discovery (Sweet Taste)

Cats are indifferent to sweet taste because the Tas1r2 gene is not functional, so the sweet taste receptor cannot be formed

In contrast to dogs (Ferrell 1984) and humans (Reed and McDaniel 2006), cats show no preference for, and indifference to, sweet compounds (such as sugars and artificial sweeteners). However the mechanism underlying this was unknown.

In collaboration with the Monell Chemical Senses Center, Philadelphia, the two genes known to be responsible for the sweet taste bud receptor in other mammals were investigated in the cat (Li et al. 2005; Li et al. 2006).

One of the genes – Tas1r3 – was expressed normally in cat taste buds (Li et al. 2005), as might be expected because it is also involved in the perception of umami taste, which cats are known to recognise. The cat Tas1r3 gene was found to be very similar to the dog (Figure 7), human, and rodent genes; at both the cDNA (74–87%) and deduced amino acid (72–85%) level (Li et al. 2006).

WDC50
Reproduced from Li X, Li W, Bayley DL, Cao J, Reed DR, Bachmanov AA, Huang L, Legrand-Defretin V, Beauchamp GK, Brand JG. Cats lack a sweet taste receptor. J Nutr 2006. 136(7Supp):1932S-1934S

Figure 5: Gene structure of Tas1r3 and Tas1r2 for cat and dog (Li et al. 2006).  The exons are shown in black (size in bp). Location (bp) refers to the position within each exon. Intron sizes shown in the ?gure are not proportionally scaled in (A) or (B) because of the large size of the Tas1r2 introns. Under each dog exon is the percentage of similarity between that exon and its cat counterpart at the nucleotide level (B). The exons for cat Tas1r2 refer to parts corresponding to dog exons. Asterisks indicate the position of microdeletion in exon 3 as well as the stop codon positions in exons 4 and 6 of cat Tas1r2. The accession for dog Tas1r3 is AY916759, and for dog Tas1r2 is AY916758

The other gene – Tas1r2 – was found to have a 247-base pair microdeletion in exon 3 and stop codons in exons 4 and 6 in the cat (Li et al. 2005). There was no evidence of detectable mRNA by reverse transcription polymerase chain reaction or in situ hybridisation, and no evidence of protein expression by immunohistochemistry (Li et al. 2005). This was the case in six healthy adult domestic cats as well as a tiger and a cheetah, and shows that, in the cat, Tas1r2 is an unexpressed pseudogene (Li et al. 2005).

Because the Tas1r2 gene is not functional in the cat, the sweet taste receptor cannot be formed and so the cat cannot taste sweet stimuli. It is likely that due to its evolution as an obligate carnivore, pressure to retain this gene was not maintained in the cat.

Discovery (Preferred Macronutrient Profile)

Cats seek out particular nutrients in their food choices

In trying to understand the complex feeding behaviour of cats, WALTHAM was inspired by research from an unusual source – insect nutrition!

Scientists at the University of Oxford, UK, (Professor Stephen Simpson [now at University of Sydney, Australia] and Professor David Raubenheimer [now at Massey University, New Zealand]) had developed a nutritional model (Geometric Framework) which they used to explain how insects such as locusts and caterpillars faced with choices of foods containing different amounts of nutrients (e.g. protein and carbohydrate) adjusted their intakes of the foods to end up consuming a particular amount of protein and a particular amount of carbohydrate. They proposed that this balance and amount of nutrients selected by animals represents their ‘intake target’ and showed that this point is associated with optimal performance, measured in terms of evolutionary fitness (Raubenheimer and Simpson 1997; Simpson et al. 2004).

So if insects regulate their macronutrient intake, what about cats?  Carnivorous animals were not thought to regulate their intake of protein, fat and carbohydrate. This was based largely on the assumption that the composition of different prey species is less variable in nutrient composition than the foods of herbivores and omnivores and such mechanisms are therefore unnecessary.

In collaboration with Professors Simpson and Raubenheimer, WALTHAM used the Geometric Framework to investigate whether cats showed evidence of regulating their macronutrient intake.

In an extensive series of feeding studies, the effect of dietary macronutrient profile (the relative amounts of protein, fat and carbohydrate) on the food intake of adult cats was investigated. For these studies, 12 nutritionally-complete diets (6 extruded [dry] and 6 canned [wet]) were specially formulated to achieve a range of macronutrient energy ratios. Cats were offered different choices of the wet foods or the dry foods in order to self-select a diet (macronutrient) composition of their choice. Geometric techniques combining mixture triangles and intake plots from the geometric framework were used to tease apart the complex interactions among protein, fat and carbohydrate in the regulation of food intake (Hewson-Hughes et al. 2011).

This research revealed strong nutritional regulation of food intake in cats and identified a target intake of approximately 26 g/day protein, 9 g/day fat, and 8 g/day carbohydrate, providing a macronutrient energy composition of 52% protein, 36% fat and 12% carbohydrate (Hewson-Hughes et al. 2011). When provided with food choices that did not allow them to achieve this target intake the cats got as close as they could by adjusting their intakes of the foods provided (Figure 8). These studies also found that cats have a limit on the amount of carbohydrate they are willing to eat in a day (~300 kJ/day which is approximately 20 g/day) – termed the ‘carbohydrate intake ceiling’ – which limits further food intake. Hence, cats confined to a high carbohydrate diet had reduced food intake and deficits in protein and energy intake relative to the target intake (Hewson-Hughes et al. 2011). Work in other species suggests that the target intake is not fixed, but may change in response to the animals’ physiological and environmental circumstances (Raubenheimer and Simpson 1997). Ongoing work at WALTHAM is investigating the target macronutrient profiles of kittens during growth and queens during gestation and lactation.

WDC51 macronutrient profile
Reproduce/adapted with permission from The Journal of Experimental Biology: Hewson-Hughes AK, Hewson-Hughes VL, Miller AT, Hall SR, Simpson SJ, Raubenheimer D. Geometric analysis of macronutrient selection in the adult domestic cat, Felis catus. J Exp Biol.2011;214(6):1039-1051

Figure 6: The influence of dietary macronutrient profile on food intake in the cat (adapted from Hewson-Hughes et al. 2011) The blue triangle encompasses the wet diet treatments, and the red star indicates the position of the intake target. The brown triangle shows dry diet treatments, with the red circle showing the intake selected by cats restricted to these diets

References

Bradshaw JWS. Mere exposure reduces cats' neophobia to unfamiliar food. Anim Behav. 1986;34(2):613-614.


Bradshaw JW, Healey LM, Thorne CJ, Macdonald DW, Arden-Clark C. Differences in food preferences between individuals and populations of domestic cats Felis silvestris catus. Appl Anim Behav Sci. 2000 Jun 1;68(3):257-268.


Bradshaw J, Thorne C. Feeding behaviour. In: The Waltham Book of Dog and Cat Behaviour. Editor: C Thorne. Pergamon Press, New York. 1992, Chapter 7, pages 115-129.


Ferrell F. Preference for sugars and nonnutritive sweeteners in young beagles. Neurosci Biobehav Rev. 1984;8(2):199-203.


Hewson-Hughes AK, Hewson-Hughes VL, Miller AT, Hall SR, Simpson SJ, Raubenheimer D. Geometric analysis of macronutrient selection in the adult domestic cat, Felis catus. J Exp Biol. 2011 Mar 15;214(Pt 6):1039-51


Li X, Li W, Wang H, Bayley DL, Cao J, Reed DR, Bachmanov AA, Huang L, Legrand-Defretin V, Beauchamp GK, Brand JG. Cats lack a sweet taste receptor. J Nutr. 2006 Jul;136(7 Suppl):1932S-1934S.


Li X, Li W, Wang H, Cao J, Maehashi K, Huang L, Bachmanov AA, Reed DR, Legrand-Defretin V, Beauchamp GK, Brand JG. Pseudogenization of a sweet-receptor gene accounts for cats' indifference toward sugar. PLoS Genet. 2005 Jul;1(1):27-35.


Mugford RA. External influences on feeding of carnivores. In: The Chemical Senses and Nutrition. Editors: MR Kare and O Maller. Academic Press, New York. 1977, Chapter 2, pages 25-48.


Mugford RA, Thorne C. Comparative studies of meal patterns in pet and laboratory housed dogs and cats. In: Nutrition of the Dog and Cat. Editor: RS Anderson. Pergamon Press, Oxford. 1980, pages 3-14.


O'Malley S. The role of variety in the diet. WALTHAM Focus. 1995;5(3):18-22.


Plantinga EA, Bosch G, Hendriks WH. Estimation of the dietary nutrient profile of free-roaming feral cats: possible implications for nutrition of domestic cats. Br J Nutr. 2011 Oct;106 Suppl 1:S35-48.


Raubenheimer D, Simpson SJ. Integrative models of nutrient balancing: application to insects and vertebrates. Nutr Res Rev. 1997 Jan;10(1):151-79.


Reed DR, McDaniel AH. The human sweet tooth. BMC Oral Health. 2006 Jun 15;6 Suppl 1:S17.


Simpson SJ, Sibly RM, Lee KP, Behmer ST, Raubenheimer D. Optimal foraging when regulating intake of multiple nutrients. Anim Behav. 2004;68:1299-1311.


Simpson SJ, Raubenheimer D. The nature of nutrition: A unifying framework from animal adaptation to human obesity. Princeton University Press, Princeton. 2012.


Thorne CJ. Feeding behaviour in the cat - recent advances. J Small Anim Pract. 1982;23(9):555-562.


Thorne CJ. Feline and canine fads. Vet Rec. 1994 Jul 9;135(2):48.


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