Ferrets are LACTOSE INTOLERANT. This means that they are unable to digest lactose, a sugar molecule found in milk.
Some people think that they can avoid this issue by giving GOAT MILK. However, Goat Milk has almost the exact same Lactose content as cow milk. Goat Milk contains fat molecules that are easier to digest, but this does not avoid the problem of lactose.
Here is an article if you want to learn more about why some PEOPLE with lactose intolerance can handle goat milk better – it is believed that many people who are “lactose intolerant” may actually be allergic to a Protein in the cow milk rather than having issues with the lactose.
Other people may say that giving your ferret Lactose-Free milk will solve the problem of indigestion due to lactose. However, this causes an entirely different issue – by giving them lactose free milk you are essentially giving them SUGAR. This isn’t a big issue in humans so I don’t think it is commonly known. Let me explain….
Lactose is a big sugar molecule made out of 2 smaller sugars (glucose and galactose) stuck together. In animals/people that are ABLE to digest lactose, there is an enzyme called Lactase that cuts the BIG sugar Lactose into the 2 smaller sugar pieces. These two smaller sugars can then be digested and used.
In animals that can NOT digest lactose (lactose intolerance) the enzyme is not there at all or there is not enough of it. This means lactose hangs around ripe for the taking – by bacteria. Because the Lactose isn’t being used by the animal, the microbes living in the gut use it instead. THE BACTERIA ingest it and release lactic acid, acetic acid, Hydrogen gas, and CO2 gas. This is what causes the diarrhea, bloating, upset stomach, etc. There is little to NO sugar actually absorbed by the animal (ferret in this case) because the bacteria use the sugar.
Now in Lactose Free milk, they ADD the enzyme Lactase to the MILK. This breaks the Big Sugar Lactose into the two smaller sugars in the milk ahead of time. For humans, this doesn’t technically affect the sugar content of the milk since it is just breaking the big sugar into the little sugars, which should happen in the intestines anyways. In ferrets however who cannot handle sugar, breaking the lactose sugar up ahead of time makes the sugar AVAILABLE FOR DIGESTION. Thus by offering your ferrets lactose free milk, you are inadvertently feeding them DIGESTIBLE SUGAR which has a very strong link to INSULINOMA.