Common Health Problems affecting Dogs and Cats

Veterinary advice from John Burns BVMS MRCVS

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A brief list of the ingredients commonly found in some pet foods.

Food Additives, Antioxidants and Preservatives.
The following is a description of food additives/preservatives found in pet food. They are not always named on the food. Sometimes the label may say 'contains EU approved antioxidant' or 'contains EEC permitted preservatives'.

Propylene glycol
It is very closely related to antifreeze. It is usually found in semi-moist foods to maintain the water content and texture. It has been suggested that it causes the destruction of red blood cells. Some studies suggest that cats can become addicted to food that contains this.

Propyl Gallate (E310)
This is antioxidant used to prevent fats and oils going rancid. It is found in chewing gum and meat products. It is banned from children's foods in the US because it is thought to cause the blood disorder methemoglobinemia.

This is used as a preservative and is thought to be one of the compounds most likely to cause damage to animal health. Ethoxyquin was developed as a rubber stabiliser. The Department of Agriculture in America lists it as a pesticide. It has been implicated as a cause of many problems including cancer of the kidneys.

Butylated hydroxytoluene (BHT)
used as a preservative to stop fat going rancid. It has been implicated as a cause of bladder and thyroid cancer and damage to the liver.

Butylated hydroxyanisole (BHA)
also used as a preservative to prevent fat rancidity. Has been implicated as a cause of stomach cancer.

Feingold (1975) found that antioxidants BHA and BHT contributed to learning difficulties and hyperactivity in humans.

In Dr. Pitcairn's (DVM, PhD) Complete Guide to Natural Health for Dogs and Cats, he looks at some of the artificial colourings in pet foods. He states that similar dyes where banned from human foods in the 1970's. The example given is Red No.2 and Violet No.1, which appeared to be linked to cancer, birth defects and skin lesions respectively.

The Asthma and Allergy Research Centre on the Isle of Wight looked at the effects of food additives and colourings and behaviour. In children significant changes in behaviour were seen when the additives (E102, E110,E122, E124 and E211) were removed from the diet for as little as 2 weeks. Does your pet food contain brightly coloured pieces?!

If your pet food states 'cereals' as a product, ask your self why? Why do they not tell you which cereals? This can be because the cereal content changes with the season depending on which is cheapest at the time.

Brown rice, oats, barley as unprocessed whole grains are high in nutrients and easily digested.

Wheat is much harder to digest than rice. Many dogs seem to be intolerant to wheat gluten. Because of this many pet foods are now wheat gluten free.

Meat content
Again if your pet food states 'meat' or 'animal' on the label, you have to ask why the company will not tell you which animal they are using?

By-products or derivatives. Many people believe that this includes beaks, feathers, hair and faeces, however, this is not necessarily true. They can include: brain, spleen, lungs, liver, blood and intestines. Poultry by-product may include feet and heads.

Chicken meal, Lamb meal etc. fresh clean meat which has been cooked, dried and ground.

How much meat is in your pet food?

For example:

If the label says 'Beef' then 70-100% must be beef.
If the label says 'Beef Dinner' then 10-70% must be beef.
If the label says 'Beef Flavour' then 0-4% must be beef
If the label says 'with Beef or contains Beef' then there must be at least 4% beef
If two or more main ingredients are stated e.g. 'Beef and Rice' then they must be 10-70% of the food (and each one must be greater than 3%)
(Burger and Thompson, 1994)

Other ingredients

Soya and other vegetable proteins are difficult to digest.

Dairy products are hard to digest. Lactose is the sugar present in milk. After weaning, dogs and cats have decreasing amounts of lactase (the enzyme needed to digest lactose). Therefore, ingestion of dairy products may cause diarrhoea and/or flatulence as the body has difficulty breaking down the dairy product. Dogs and cats should not be fed milk and cheese!

Sugars are sometimes added to cat foods as a flavour enhancer. Sugar and sugar products are not good sources of nutrition for cats, and can contribute to dental disease

Yoghurt is sometimes used for therapy of chronic diarrhoea in the mistaken belief that the bacteria contained in yoghurt (Lactobacillus acidophilius or Lactobacillus bulgaricus) will colonise the bowel and displace unfavourable bacteria.

Yoghurt has bacteriocidal properties in vitro (test tube) but not in vivo (in the body). Orally administered bacteria in yoghurt does not displace resident or pathogenic bacterial populations in normal or diseased intestines of any animal. The bacteria in yoghurt are generally acid labile (destroyed by the stomach acid), limiting the numbers surviving passage through the stomach. (Research originally published in the Journal of Small Animal Practice Vol. 35).



BSAVA Manual of Companion Animal Nutrition and Feeding, First Edition, Edited by N.C. Kelly and J.M.Wills. Pub, BSAVA 1996.

Small Animal Clinical Nutrition, 4th Edition, By Hand, Thatcher, Remillard and Roudebush. Pub, Mark Morris Institute 2000.

Dr. Pitcairn's Complete Guide to Natural Health for Dogs and Cats, By Richard H. Pitcairn, DVM PhD, Susan Hubble Pitcairn MS. Pub, Rodale Press, Inc. 1995.


Common pet health problems
John Burns Pet Health Management Programme




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