Lactose intolerance is an inability to digest the sugar lactose, which is mainly found in dairy products.
Erin Dowler (veterinarian) – May 2014
Puppies initially have the ability to digest lactose. However, after weaning the level of the enzyme lactase (which is needed to digest lactose) reduces to 10% of its original level. Some dogs no longer have any enzyme and are completely intolerant.
Diarrhoea occurs if a dog ingests more lactose than they can ingest.
Diagnosis is by a trial where exclusion of dairy products resulting in resolution of diarrhea. If re-introducing dairy products causes the diarrhea to occur, this is likely the cause.
Dairy products need to be excluded. Sometimes additional management for diarrhea may be required while the dog recovers, such as an easily digestible diet and gastroprotectants.
Do not feed dogs excessive dairy products.
Pet milk is available which is lactose free.