Some Pets Unable to Tolerate Dairy Products

October 23, 2012

While milk is not necessary to a dog's (or cat's) diet, it can be a treat if given from time to time.  However, some pets cannot tolerate milk because they do not produce an enzyme called "lactase". Lactase helps with the digestion of lactose, which is found in milk. After weaning, the level of lactase activity falls to about 10 per cent of its peak activity. In some animals, diarrhoea will occur if more lactose (i.e. milk) is consumed than the pet can digest. This is called "lactose intolerance".

A further contributing factor is the fact that cow and goat milk contains 4.5 to 5 per cent lactose, compared to 3.1 per cent in a bitch's milk (lactating female dogs) and 4.2 per cent in a queen's milk (lactating female cats). The high level of lactose in cow's milk can overpower a dog or cat's ability to digest it. This is why many pups and kittens often get diarrhoea from drinking cow's milk.  This does not mean that milk is unhealthy for dogs and cats. On the contrary, in pets that are able to tolerate it, milk can be an excellent source of protein and calcium.   

Pets with milk intolerance can still partake of dairy products under certain circumstances. For example, dairy products such as cheese (including cottage cheese) and unpasteurized yoghurt usually have the lactose removed or have it partially broken down through bacterial action. As a result, these products are often well tolerated by cats and dogs that would otherwise get diarrhoea after drinking milk.

It should be stated that neither boiling milk nor the use of skim milk affects an animal's ability to tolerate milk, since the lactose content remains unchanged in either case.  The same applies to pasteurised yoghurt and cultured milk (e.g. buttermilk), neither of which is well tolerated by lactase-deficient pets.

If a dog or cat has loose stools whenever milk is fed, that pet is likely to be lactose intolerant and milk should be withheld.  It is also wise to advise your veterinarian of this fact and discuss the potential implications involved with regard to your pet.