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Supplement: Waltham International Symposium

Aging Does Not Influence Feeding Behavior in Cats

Sarah E. Peachey^*, and E. Jean Harper^3,

^* School of Biological Sciences, University of Nottingham, Sutton Bonnington Campus, Leicestershire, UK and Waltham Centre for Pet Nutrition, Leicestershire, UK

³To whom correspondence should be addressed. E-mail: jean.harper{at}eu.effem.com.

	ABSTRACT

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
The aim of this investigation was to see whether aging influences feeding behavior in cats. Two studies were carried out. In the first study, a standard canned cat food was fed to six young adult and six senior cats for 10 d on an ad libitum basis. Feeding behavior was monitored during the final 5 d. In the second study, diets enriched with beef tallow, olive oil or sunflower oil were fed at an equivalent energy intake for 21 d. Feeding behavior was monitored during the final 5 d. The results of both studies indicated no significant differences between the young and old cats in the number of meals consumed, the amount consumed at each meal or the duration of each meal when fed either ad libitum or at equivalent energy intakes. Daily feeding patterns were similar for each of the 5 d for each cat, with cats tending to consume regular small meals throughout the day and night. The only significant differences noted were among the fat-enriched diets. The diet enriched with beef tallow had fewer refusals compared to the diets enriched with olive oil and sunflower oil, indicating a possible palatability differential. It was concluded that cats of all ages are habitual feeders with similar daily feeding patterns, which may be altered only with a change in diet. Given that no differences were seen between the young and senior cats, it cannot be assumed that feeding patterns are responsible for the previously observed age-related decreases in apparent digestibility.

KEY WORDS: • feeding behavior • feline • digestibility • age • energy intakes

It is well documented that in humans and rats, nutrient digestibility and absorption decline with age (1–3). This decline happens in apparently healthy subjects and is not a manifestation of an underlying clinical condition. The effect of aging on nutrient digestibility has been reported in adult cats fed a standard canned cat food (4,5). Significant decreases in apparent digestibility of protein, fat and energy have been observed with an increase in age. In addition to the decreases in apparent digestibility, it has been observed that older cats tend to increase their daily food intake, possibly as a compensatory mechanism for diminished digestive capacity.

Feeding behavior is dependent on a number of factors such as palatability, hunger (physiological state) and appetite (desire to eat). Palatability is the degree of acceptability of a foodstuff to an animal and relies on the sensory acceptance of a food by the animal. Palatability relies on taste, odor, appearance, temperature and texture, and the combination of these factors influences the animal’s acceptance or rejection of a food.

Cats are obligate carnivores, and their food preference would be freshly killed carcasses, rather than carrion (6). In keeping with their carnivorous diet, cats seem to have no perception of sweet substances, showing no liking for sugar or artificial sweetener solutions compared to plain water (7). The fat composition of a predatory diet is relatively high (6–18% as is), and canned cat diets have a typical fat content of 20–30% dry matter basis. Fat is important for the taste and texture of a diet, and cats show no taste preferences between diets containing either 15 or 45% fat (8). However, evidence suggests that cats prefer some fat sources to others. When cats were fed diets enriched with bleached tallow, chicken fat or butter, all cats had a greater intake of bleached tallow compared to the chicken fat or butter (9).

The aim of this study was to investigate the effect of aging on feeding behavior in cats. Any such changes might explain the previously reported age-related decreases in apparent digestibility of nutrients (5). If, for example, the older cats ate larger meals, the ability of the gastrointestinal tract to cope with the large influx of nutrients may be impaired. A nibbling pattern, however, allows a steady influx of nutrients into the gastrointestinal tract, allowing maximal digestion and absorption. A difference in feeding pattern, therefore, could account for a difference in nutrient utilization. A standard canned cat food was fed ad libitum, and diets enriched with beef tallow (BT), olive oil (OO) or sunflower oil (SO) were fed at equivalent energy intakes to investigate the effects of age and diet palatability on feeding behavior.

	MATERIALS AND METHODS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
To investigate the effects of age on feeding behavior, six young adult (3.0 ± 0.9 y) and six senior (11.6 ± 1.4 y) female neutered cats were individually housed in a controlled environment with a temperature of 22 ± 2°C and were exposed to 11 h of darkness between 1900 and 0600 h (10). They were fed a standard canned cat food (Whiskas^®, Pedigree Masterfoods, Melton Mowbray, UK) for a period of 10 d (Table 1), with feeding behavior monitored during the final 5 d. The cats were offered 400 g/d, which was increased if necessary to ensure they were eating to appetite. They had access to this food from 1100 until 0830 h the next day, when food bowls were removed and refusals weighed. They were given unlimited access to water.

Feeding rates were measured using specifically designed load cells (developed and made by Pedigree Electronics^TM, Melton Mowbray, UK) to investigate the feeding behavior of cats. Food was placed onto the load cell and weights were recorded every 3 s onto a PCMCIA memory card. The start of a meal was defined as three consecutive readings recording a decrease in food weight. This allowed for external influences on the balance, such as evaporation. The end of a meal was defined as 10 consecutive readings without any weight loss. The information from the memory card was analyzed to determine meal size, meal frequency, meal duration and rate of eating. Both studies conformed to the guidelines of the Waltham Ethical Review Committee.

Statistical analysis

The effect of age on feeding behavior when fed ad libitum was tested using one-way analysis of variance (ANOVA, Genstat 5 for Windows; Lawes Agricultural Trust, 1989). Because each cat was monitored on five separate occasions, the effect of cat was blocked. Because of an electrical fault with one balance there are missing data for one cat (young group, study 1); thus the residual degrees of freedom were 9 instead of 10.

The effects of age and diet on feeding behavior during the 3 x 3 Latin square design were tested in a two-factor split-plot ANOVA, with cats as the main plots, the main effect of age being tested against the variance between cats. The effects of period, diet and diet x age interactions were tested against the within-cat error. Differences were assumed to be statistically significant at P < 0.05.

	RESULTS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
The macronutrient profiles of the four diets on a dry matter basis are shown in Table 1. The diets enriched with beef tallow, olive oil or sunflower oil were around 36% more energy dense than standard canned cat food.

Table 2 presents the mean number of meals consumed, the meal duration and intake data for young (n = 5) and senior (n = 6) cats when fed a standard canned cat food ad libitum. No significant differences were observed between the young and senior cats for feeding behavior when food was offered ad libitum, although younger cats tended (P = 0.07) to consume larger meals than the senior cats (29.18 compared to 19.30 kJ/kg^0.75BW, respectively). The rates of feeding however, were not different between the two age groups: 19.97 and 18.13 kJ/kg^0.75BW/min for young and senior cats, respectively.

View larger version (28K): [in this window] [in a new window]   FIGURE 1 Meals consumed within 4-h time periods over 22 h for young (n = 5) and old (n = 6) cats fed standard canned diet. Data are calculated as 5-d mean for each cat, then averaged per group (± SD).

View larger version (16K): [in this window] [in a new window]   FIGURE 2 Mean (n = 5 d) hourly cumulative food intakes over 22 h for young (n = 5) and old (n = 6) cats fed standard canned diet.

The diet enriched with beef tallow had significantly (P < 0.05) higher energy intakes in both young and senior cats (267 and 285 kJ/kg^0.75BW/d, respectively). By comparison, energy intake of the diet enriched with sunflower oil was 240 and 258 kJ/kg^0.75BW/d (young and senior cats, respectively) and of that enriched with olive oil, 226 and 254 kJ/kg^0.75BW/d (young and senior cats, respectively).

Figures 3 and 4present the mean hourly cumulative intakes for young (n = 6) and senior (n = 6) cats for the 22-h period during which food was available (mean of 5-d observations). Both groups of cats tended to consume very similar amounts of each diet and there were no age x diet interactions with respect to cumulative intakes over the day.

View larger version (29K): [in this window] [in a new window]   FIGURE 3 Mean (n = 5 d) hourly cumulative food intakes by senior cats (n = 6) fed diets enriched with beef tallow (BT), sunflower oil (SO) or olive oil (OO).

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

The aim of this study was to investigate whether aging influences feeding behavior and, additionally, whether such changes could contribute to the previously observed decreases in apparent digestibility of nutrients with age (4,11). If, for example, the older cats ate larger meals, the ability of the gastrointestinal tract to cope with the large influx of nutrients may be impaired. A nibbling pattern, however, allows a steady influx of nutrients into the gastrointestinal tract, allowing maximal digestion and absorption. No significant differences were seen between young and senior cats in the number of meals consumed, the amount at each meal or the duration of each meal when fed either unrestricted or equivalent amounts. Daily feeding patterns were similar for each of the 5 d for each cat, and the only differences between the fat-enriched diets were the lower intakes of the diets enriched with olive oil and sunflower oil. These results confirm those of Kane et al. (9), who demonstrated a preference in cats for beef tallow compared to vegetable fat. It should be noted that the fat levels in the diets fed in the present study were unusually high and are likely to have produced an extreme response in the cats.

Daily intakes were higher in cats allowed unrestricted access to the food compared to those when fed an equivalent energy level (up to 351 g/d compared to up to 170 g/d when fed the beef tallow–enriched diet). On a kJ/kg^0.75BW/d basis the intakes were up to 385 kJ/kg^0.75BW/d when fed ad libitum, compared to up to 285 kJ/kg^0.75BW/d when fed the beef tallow–enriched diet. When cats were fed canned products with a varying energy content (13), it was demonstrated that the mean energy intakes per meal were similar, even when the canned product was swapped for a more energy dense dry diet. The energy intake per meal remained consistent, even though the meal intake in grams was reduced by about 25%. The cats showed a repetitive feeding behavior, tending to consume regular small meals throughout the day and night. This result confirms findings in cats, rats and guinea pigs, where it was reported that if allowed free access to food, a nibbling pattern of several small meals throughout the day and night was adopted, compared to a pattern of fewer, larger discrete meals. Meal size is reported to show little relationship to the size of the preceding meal or to the length of the interval between feedings (12,14). The effect of age has not been reported by any author.

These studies indicate that cats of all ages exhibit similar daily feeding patterns. A change in diet may elicit a change in food intake but in these studies a change of diet did not alter feeding behavior. There were no differences in feeding patterns between young and senior cats. Thus it cannot be assumed that previously observed age-related decreases in nutrient digestibility are related to feeding behavior. Because all cats tended to consume small regular meals throughout the 22-h period, the influx of nutrients into the gastrointestinal tract is likely to be steady, allowing maximal digestion and absorption to occur.

View larger version (27K): [in this window] [in a new window]   FIGURE 4 Mean (n = 5 d) hourly cumulative food intakes by young cats (n = 6) fed diets enriched with beef tallow (BT), sunflower oil (SO) or olive oil (OO).

	ACKNOWLEDGMENTS

	FOOTNOTES

 
¹ Presented as part of the Waltham International Symposium: Pet Nutrition Coming of Age held in Vancouver, Canada, August 6–7, 2001. This symposium and the publication of symposium proceedings were sponsored by the Waltham Centre for Pet Nutrition. Guest editors for this supplement were James G. Morris, University of California, Davis, Ivan H. Burger, consultant to Mars UK Limited, Carl L. Keen, University of California, Davis, and D’Ann Finley, University of California, Davis.

² Supported by BBSRC (Biotechnology and Biological Sciences Research Council) and the Waltham Centre for Pet Nutrition under a C.A.S.E. (Co-operative Awards in Science and Engineering) studentship.

⁴ Abbreviations used: BT, beef tallow; BW, body weight; ME, metabolizable energy; NFE, nitrogen-free extract; OO, olive oil; SO, sunflower oil.

	LITERATURE CITED

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

1. Webster, S.G.P., Wilkinson, E. M. & Gowland, E. (1977) A comparison of fat absorption in young and old subjects. Age Ageing 6:113-117.[Abstract/Free Full Text]

2. Montgomery, R. D., Haeney, M. R., Ross, I. N., Sammons, H. G., Barford, A. V., Balakrishnan, S., Mayer, P. P., Culand, L. S., Field, J. & Gosling, P. (1978) The aging gut: a study of intestinal absorption in relation to nutrition in the elderly. Q. J. Med. 47:197-211.[Abstract/Free Full Text]

3. Holt, P. R. & Dominquez, A. A. (1981) Intestinal absorption of triglyceride and vitamin D3 in aged and young cats. Dig. Dis. Sci. 26:1109-1115.[Medline]

4. Taylor, E. J., Adams, C. & Neville, R. (1995) Some nutritional aspects of aging in cats and dogs. Proc. Nutr. Soc. 54:645-656.[Medline]

5. Harper, E. J. (1998) Changing perspectives on aging and energy requirements: aging and digestive function in humans, dogs and cats. J. Nutr. 128:2632S-2635S.[Abstract/Free Full Text]

6. Scott, P. P. (1968) The special features of nutrition of cats, with observations on wild Felidae nutrition in London Zoo. Symp. Zool. Soc. London 21:21-36.

7. Beauchamp, G. K., Maller, O. & Rogers, J. G. (1977) Flavour preferences in cats (Felis Catus and Panthera sp). J. Comp. Biochem. Physiol. Psychol. 91:1118-1127.

8. Kane, E., Leung, P.M.B., Rogers, Q. R. & Morris, J. G. (1987) Diurnal feeding and drinking patterns of adult cats as affected by changes in the level of fat in the diet. Appetite 9:89-98.[Medline]

9. Kane, E., Morris, J. G. & Rogers, Q. R. (1981) Acceptability and digestibility by adult cats of diets made with various sources and levels of fat. J. Anim. Sci. 53:1516-1523.

10. Loveridge, G. G., Horrocks, L. J. & Hawthorne, A. J. (1995) Environmentally enriched housing for cats when housed singly. Anim. Welfare 4:135-141.

11. Peachey, S. E., Dawson, J. M. & Harper, E. J. (1999) The effect of aging on nutrient digestibility in cats fed beef tallow–, sunflower oil–or olive oil–enriched diets. Growth Dev. Aging 63:49-58.[Medline]

12. Mugford, R. A. & Thorne, C. (1980) Comparative studies of meal patterns in pet and laboratory housed dogs and cats. Anderson, R. S. eds. Nutrition of the Dog and Cat 1980:3-14 Pergamon Press Oxford, UK. .

13. Thorne, C. J. (1982) Feeding behavior in the cat—recent advances. J. Small Anim. Pract. 23:555-561.

14. Hirsch, E. (1978) Dietary control of food intake in cats. Phys. Behav. 20:287-298.[Medline]

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Peachey, S. E. Articles by Harper, E. J. Search for Related Content PubMed PubMed Citation Articles by Peachey, S. E. Articles by Harper, E. J.