NYSVMS Veterinary News Interviews Dr. Peterson About His Endocrine Textbook

How to Feed Cats: Examining the Nutrition of Feral Cats

Paper Review: The Nutrition of Feral Cats 

Estimation of the dietary nutrient profile of free-roaming feral cats: possible implications for nutrition of domestic cats. 

British Journal of Nutrition 2011;106 Suppl 1:S35-48. 

by E.A. Plantinga, G. Bosch, and W.H. Hendriks 

Abstract
Cats are strict carnivores and in the wild rely on a diet solely based on animal tissues to meet their specific and unique nutritional requirements. Although the feeding ecology of cats in the wild has been well documented in the literature, there is no information on the precise nutrient profile to which the cat's metabolism has adapted.

The present study aimed to derive the dietary nutrient profile of free-living cats. Studies reporting the feeding habits of cats in the wild were reviewed and data on the nutrient composition of the consumed prey items was obtained from the literature.

Fifty-five studies reported feeding strategy data of cats in the wild. After specific exclusion criteria, twenty-seven studies were used to derive thirty individual dietary nutrient profiles. The results show that feral cats are obligatory carnivores, with their daily energy intake from crude protein being 52%, from crude fat 46% and from N-free extract (i.e., carbohydrates) only 2%. Minerals and trace elements are consumed in relatively high concentrations compared with recommended allowances determined using empirical methods.

The calculated nutrient profile may be considered the nutrient intake to which the cat's metabolic system has adapted. The present study provides insight into the nutritive, as well as possible non-nutritive aspects of a natural diet of whole prey for cats and provides novel ways to further improve feline diets to increase health and longevity.

My Comments 
In this excellent study (1), the researchers reviewed 27 published studies reporting the feeding habits of feral cats and obtained data on the nutrient composition of the cats’ prey. The results showed that feral cats are obligatory carnivores with a diet high in protein (52% of daily energy) and fat (46% of daily energy) content, but low in carbohydrates (2% of daily energy). The results of this study should be expected since it has long been recognized that cats are strict carnivores, with a high dietary need for protein and fat but no dietary need for carbohydrates (2-5).

The typical prey diet of cats is low in carbohydrate (<10% of metabolizable energy (ME) (6-9). However, most commercially available cat foods are moderate to high in carbohydrate content (> 25 – 55 % ME), partly because of the difficulty in formulating extruded, dry diets that are low in carbohydrate. But higher carbohydrates are also used in cat food diets because cereal is a relatively inexpensive ingredient, and there is demand for lower-cost diets in the pet food market.

I believe strongly that many of the present-day diseases of the domestic cat are related to an "unnatural" diet, one too high in carbohydrates and too low in protein and fat. I believe we should be feeding our cats closer to what they would be eating in the wild, at least if they do not have special nutritional needs because of diseases such as kidney disease. Future research should focus on the value of feeding a natural diet of whole prey as a means of enhancing both feline health and longevity.

The authors should be commended for doing this excellent study and publishing the results. Hopefully, the pet food industry will pay attention.

References:

1. Plantinga EA, Bosch G, Hendriks WH. Estimation of the dietary nutrient profile of free-roaming feral cats: possible implications for nutrition of domestic cats. British Journal of Nutrition 2011;106 (Suppl 1):S35-48.
2. MacDonald ML, Rogers QR, Morris JG. Nutrition of the domestic cat, a mammalian carnivore. Annual Review of Nutrition 1984;4:521-562.
3. Zoran DL. The carnivore connection to nutrition in cats. Journal of the American Veterinary Medical Association 2002;221:1559-1567. 
4. Morris JG. Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations. Nutrition Research Reviews 2002;15:153-168. 
5. Bradshaw JWS. The evolutionary basis for the feeding behavior of domestic dogs (Canis familiaris) and cats (Felis catus). Journal of Nutrition 2006;136:1927S–1931S.
6. Myrcha A, Pinowski J. Weights, body composition and caloric value of post-juvenile molting European tree sparrows. Condor 1970;72:175–178.
7. Vondruska JF. The effect of a rat carcass diet on the urinary pH of the cat. Companion Animal Practice 1987;1:5-9.
8. Crissey SD, Slifka KA, Lintzenich BA. Whole body cholesterol, fat, and fatty acid concentrations of mice (Mus domesticus) used as a food source. Journal of Zoo and Wildlife Medicine 1999;30:222-227.
9. Eisert R. Hypercarnivory and the brain: protein requirements of cats reconsidered. Journal of Comparative Physiology B, 2011;181:1-17.

Antithyroid Drug Treatment Can Induce Remission of Hyperthyroidism in Humans But Not Cats

In humans, Graves' disease is the most common cause of hyperthyroidism in both adults and children (1). Graves' Disease is caused by the patient's immune system producing an antibody that attacks and turns on the thyroid.

One of the goals of treating patients with antithyroid medications is the hope that these drugs may cause the immune system to stop producing the antibody, resulting in the Graves' Disease going into remission (1). In a recent study of children with Graves' disease, up to 50% of these young patients experienced remission of their hyperthyroidism (2).

This is completely different than the situation we see in cats with hyperthyroidism. Cats do not develop Graves' Disease (3-8). Rather, hyperthyroidism in cats is caused by one or more thyroid tumors (see my blog post, Do All Hyperthyroid Cats Have a Thyroid Tumor?). These thyroid tumors are generally benign (adenomas) but can rarely become malignant.

Although cats frequently are treated for prolonged periods with antithyroid drugs to lower their high circulating thyroid levels and manage their hyperthyroidism, these cats will never go into remission (5-9). For more information on the advantages and disadvantages of using antithyroid drugs in hyperthyroid cats, see my blog post, Treating Cats with Hyperthyroidism: Antithyroid Drugs).

References

1. Cooper DS. Antithyroid drugs. New England Journal of Medicine 2005;352:905-917.
2. Léger J, Gelwane G, Kaguelidou F, French Childhood Graves' Disease Study Group. Positive impact of long-term antithyroid drug treatment on the outcome of children with Graves' disease: national long-term cohort study. Journal of Clinical Endocrinology and Metabolism 2012;97:110-119. (summarized here in Clinical Thyroidology for Patients).
3. Gerber H, Peter H, Ferguson DC, et al. Etiopathology of feline toxic nodular goiter. Veterinary Clinics of North America Small Animal Practice 1994;24:541-565.
4. Peterson ME, Ward CR. Etiopathologic findings of hyperthyroidism in cats. Veterinary Clinics of North America Small Animal Practice 2007;37:633-645.
5. Peterson ME: Hyperthyroidism in cats. In: Melian C (ed): Manual de Endocrinología en Pequeños Animales (Manual of Small Animal Endocrinology). Barcelona, Multimedica, 2008; 127-168.
6. Baral R, Peterson ME. Thyroid gland disorders. In: Little, S.E. (ed), The Cat: Clinical Medicine and Management. Philadelphia, Elsevier Saunders 2012; 571-592.
7. Mooney CT, Peterson ME: Feline hyperthyroidism, In: Mooney C.T., Peterson M.E. (eds), Manual of Canine and Feline Endocrinology (Fourth Ed), Quedgeley, Gloucester, British Small Animal Veterinary Association, 2012;92-110.
8. Peterson ME: Hyperthyroidism in cats, In: Rand, J (ed), Clinical Endocrinology of Companion Animals. New York, Wiley-Blackwell, 2012; in press.
9. Peterson ME, Kintzer PP, Hurvitz AI. Methimazole treatment of 262 cats with hyperthyroidism. Journal of Veterinary Internal Medicine 1988;2:150–157. 

Can Chronic Stress and Cortisol Resistance Make Your Pet Sick?

It is well known that chronic stress and illness are related. For example, psychological stress in humans raises the risk of heart disease, colds and flu. And chronic stress in animals is also well known to lead to diseases such as upper respiratory or lower urinary tract infections.

But how does such stress lead to illness? New research published recently in the Proceedings of the National Academy of Sciences (1) found that the adrenal hormone cortisol plays a critical role in the illness caused by stress.

Released in greater amounts in times of stress, cortisol helps suppress the body’s immune response to infections, suppressing inflammation responses like coughing, sneezing, or fever. But when levels of cortisol remain high, the body may become less sensitive to it — a condition called cortisol or glucocorticoid "resistance."

So in other words, when we are stressed out, we overproduce cortisol, making our immune system incapable of turning "off" the inflammation response. If we're exposed to a virus while we are also dealing with chronic stress, the study found that we'd also be much more likely to get sick and suffer from more intense symptoms (1).

In other words, many of the symptoms of a cold, for example, are not caused directly by the virus, but rather, they're caused by the inflammatory response to the infection. We want the body to produce enough of inflammation to fight off the infection, but not so much that we experience worsened symptoms.

The Bottom Line:
Chronic stress may raise the risk of sickness by creating a state of resistance to the hormone cortisol, which, in turn, interferes with appropriate regulation of inflammation.  Because inflammation plays an important role in the onset and progression of a wide range of diseases, this model may have broad implications for understanding the role of stress in health.

Although we do no know if the same phenomenon of stress-induced cortisol resistance exists in animals, it is certainly possible. We certainly do know that physical and psychological stress can induce disease in domestic animals (2-4).

References:

1. Cohen S, Janicki-Deverts D, Doyle WJ, et al.  Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk.  Proceedings of the National Academy of Sciences (PNAS) 2012; ,doi:10.1073/pnas.1118355109.
2. Westropp JL, Kass PH, Buffington CA. Evaluation of the effects of stress in cats with idiopathic cystitis. American Journal of Veterinary Research 2006;67:731-6.
3. McCobb EC, Patronek GJ, Marder A, et al. Assessment of stress levels among cats in four animal shelters. Journal of the American Veterinary Medical Association 2005;226:548-555.
4. Stephens DB. Stress and its measurement in domestic animals: a review of behavioral and physiological studies under field and laboratory situations. Advanced in Veterinary Science and Comparative Medicine 1980;24:179-210.