ABSTRACT: The evolution of the cat – from opportunistic rodent-eating hunter to indoor companion with ready access to meals – has coincided with an increased lifespan and health. However, the cat remains unique in many of its dietary needs and in the way il generates energy, with specific requirements for certain nutrients. Its carnivorous metabolism, reinforced by historical access to a diet of animal-based tissues and very little carbohydrate, have meant that some of its enzyme systems are limited in their capacity – or lacking altogether. This has led to an absolute need for certain essential nutrients from animal flesh in the food and supplementation with others. The growth life-stage phase sees some further requirements, with an increased need for energy and protein, along wilh certain nutrients. Many commercial diets now provide an easy-to-feed, balanced way of providing these essential nutrients to take the kitten from a vulnerable post-weaning stage through lo a healthy adult.

The goal of feeding a kitten in its early stage of life – from completion of weaning at about eight weeks to a fully grown adult cat at about 10-12 months – is to produce a healthy adult with minimal risk factors for disease. Foods for this age group have become increasingly sophisticated with technological advances in digestibility and the inclusion of ingredients proven to enhance immunity.

Specific needs


The cat’s digestive system and metabolism have evolved to have very specific requirements which are markedly different from dogs. The cat is an obligate carnivore and, therefore, needs to have some animal-based ingredients in its diet.

In the wild this consists of flesh and animal-based tissues, often with quite poor protein digestibility and little or no digestible carbohydrate. The lack of readily available glucose from limited carbohydrate has led to the adaptation of the liver to produce glucose from the breakdown components of protein –   amino acids.

The hepatic enzyme system (transaminases and deaminases) strip amino groups from the amino acids resulting in the formation of keto-acids, which then enter the biochemical pathway that leads to the generation of energy. These gluconeogenic enzymes are always active in the cat (unlike in dogs) and so this species needs a constant source of protein in its diet.

The glucokinase system, which helps to convert glucose from carbohydrates, has low activity in cats (because of the traditionally restricted supply of carbohydrates), which limits their ability to metabolise large amounts of simple carbohydrates.

During the growth phase, a kitten requires an increased amount of protein in its diet. This is to supply readily available amino acids for day-to-day maintenance, as well as building new body components, such as hormones, enzymes, antibodies, lean muscle, skin and organ tissues. There is also a need for specific essential amino acids, which kittens need in greater amounts than other species.

It is recommended that kitten foods contain a level of crude protein in the range of 35 to 50 per cent dry matter (DM) for healthy growth. Most commercial diets formulated for kittens will fall within this range.

Essential amino acids

Cats need a specific supply of certain amino acids in their diet. These so-called essential amino acids are those which the cat cannot synthesise itself from other biological components.

Arginine is one such essential amino acid. A deficiency is quickly manifested as hyperammonaemia because of its essential role in the urea cycle. Fortunately this is very rare as most cats will either eat a commercial diet or one high in animal- based tissues.

Another important amino acid in the cat is taurine. The requirement for this component is particularly high owing to an obligatory loss in bile salts. While taurine is found in abundance in the natural prey of cats, such as rodents and birds, it is less abundant in large animal species, such as cattle, and, therefore, has to be supplemented.

The kitten life-stage also sees an increased need for the sulphur- containing amino acids – methionine and cysteine. Of these, methionine is considered essential as some cysteine can be made from it. Although animal-based tissues contain an abundance of methionine, kittens have a high requirement and deficiencies are possible, particularly in those individuals fed home-made or vegetable-based diets.

About 19 per cent of a food must be composed of animal protein to meet the methionine requirements of kittens.1

Essential fatty acids (EFAs)

Just as certain amino acids are considered essential, so too are some fatty acids.

Growth creates a high demand for arachidonic acid (AA), which cats (unlike dogs) have limited ability to synthesise from linoleic acid (LA). They have low hepatic delta-6-saturase activity – the enzyme that converts linoleic acid to y- linolenic acid, which is elongated and further desaturated to form AA. The inclusion of animal-based ingredients helps to ensure an adequate supply of AA.

Along with linoleic and arachidonic acid, kittens have a need for some omega-3 fatty acids. Docosahexaenoic acid (DHA) has been shown to be essential for the optimal development of the neural, retinal and auditory systems in the cat.2

An interesting study by Kelley et al. (2004) showed that puppies receiving additional amounts of DHA in their diet were able to learn better and were more trainable.3 Given that the cat is less able to produce DHA than the dog, it may be that kittens have an even greater need for this than puppies. The mother is able to pass some DHA in utero and through milk, but quantities are ensured by supplementing growth diets, usually with fish oils.


Although cats can synthesise niacin, breakdown in the cat exceeds the rate at which it can be synthesised and, therefore, cats have a higher need for it than dogs. Again, an animal-based diet fulfils this need. Vitamin B6 is also required in increased amounts owing to its inclusion in transaminase enzymes, which are part of the constant active enzyme hepatic system referred to earlier.

In other species, vitamin A can be synthesised from the precursor (3-carotene, which is found in plants. Cats are unable to convert (J-carotene to vitamin A owing to a lack of an intestinal enzyme, and so a direct source of this vitamin is required.

A source of vitamin D is also essential, given the cat’s insufficient ability to convert it from precursors in the skin. Animal tissues and fats help to supply these extra vitamins, reinforcing the carnivorous needs of the cat.

Fat in itself is a useful source of energy, which is particularly valuable during the growth life stage. However, while dietary fat helps to supply much needed fat- soluble vitamins and EFAs, care needs to be taken to avoid obesity. Regular assessment of body weight and body condition scoring should be carried out and adjustments in feeding quantities made to achieve an ideal body weight.

Bone development

While the developmental bone diseases associated with excessive dietary calcium in puppies are not seen in kittens, there is still a need to be careful with calcium levels. Too much calcium can reduce the availability of magnesium and levels of 0.8 to 1.6 per cent are recommended.4 Phosphorus levels of 0.6 to 1.4 per cent DM are also recommended, leading to calcium:phosphorous ratios of 1.1:1 to 1.5:1.

Home-made diets with very high meat content are increasingly being fed by many pet owners, in an attempt to mimic a cat’s natural diet. However, the lack of supplementation with sufficient calcium to counter the high phosphorus intake can lead to nutritional
secondary hyperparathyroidism with consequent bone disease. Limping and pain are often the presenting signs and, following an appropriate veterinary examination to confirm the diagnosis, the diet of these patients should be corrected quickly. 

Boosting immunity

Recent advances in pet food for kittens have seen the inclusion of antioxidants to help support the development of a healthy immune system. Additionally, some manufacturers have utilised components of colostrum in kitten food to help stabilise the developing guts microflora, which is particularly vulnerable and prone to diarrhoea.

Correct nutrition plays a vital role in the development of the kitten and many of the benefits acquired during this lifestage help to equip the cat with the right defences and body systems to cope with life as a healthy adult. 


Libby Sheridan MVB MRCVS

Libby graduated as a vet from University College Dublin in Ireland and spent 10 years working in mixed and small animal practice, followed by 7 years as the UK & Ireland Veterinary Affairs Manager for leading pet food manufacturer, Hill's Pet Nutrition. She founded Mojo in 2008 (www.mojoconsultancy.com), an agency providing marketing, project and PR consultancy to the veterinary and petcare market.

To cite this article use either

DOI: 10.1111/j.2045-0648.2012.01182.x or Veterinary Nursing Journal Vol 27 pp 232-234


1.   MacDONALD. M. L. ROGERS. Q R. and MORRIS. J. 6. [1984] Nutrition of the domestic cat, a mammalian carnivore. Annual Review of Nutrition 4: 521-562.

2.   PAWLOSKY. R. J„ DENKIN. Y„ WARD. G. et al (1997) Retinal and brain accretion of long-chain polyunsaturated fatty acids in developing felines: The effects of corn oil-based maternal diets. American Journal of Clinical Nutrition 65: 465¬472.

3.   KELLEY. R. L.. LEPINE. A. J.. BURR. J. R. et al., [2004] Effect of dietary fish oil on puppy frainability. 6th Congress of the International Society for the Study of Fatty Acids and Lipids 2004: 45338.

4.   HOWARD. K. A.. ROGERS. Q. R. and MORRIS. J. G. [1998] Magnesium requirement of kittens is increased by high dietary calcium [Abstract). Journal of Nutrition 128: 2601 S.

Useful Reading

Small Animal Clinical Nutrition 5th Ed. 2010. Mark Morris Institute. Good reference book on lifestage and clinical nutrition.

Encylopedia of Feline Clinical Nutrition. Pibot. Biourge and Elliot [2010]. Has an interesting chapter on the feeding behaviour of the cat and how kittens learn food preferences from their mothers.

Veterinary Nursing Journal • VOL 27 • June 2012 •