Feeding hamsters milk

Feeding milk to hamsters or other animals is not recommended. All mammals become lactose intolerant once they have been weaned. This is because once weaned an animal does not produce enough of the enzyme Lactase: Lactase is an enzyme in the small intestine that is needed to digest the lactose: Lactose is the natural sugars found in milk. It is this sugar that will cause anything from loose, green or yellow stools, to diarrhea in a hamster. It should be noted that boiling the milk or the use of skimmed milk will not affect the hamsters' ability to tolerate milk since the lactose content remains unchanged.

Once hamster pups have been fully weaned from the mothers milk at around 21 day's, the level of lactase production falls to about 10 per cent of its pre weaning level. In hamsters diarrhea will occur if more lactose (milk) is consumed than the hamster can digest, this is known as "Lactose intolerance".
Hamsters' and other pets' that are lactose intolerant can still consume dairy products such as cheese, this includes cottage cheese and un-pasteurized yogurt etc: These items usually have the lactose removed or partially broken down through bacterial action. As a result these products are often well tolerated by pets' that would otherwise experience diarrhea after consuming milk.