There are confusing messages about feeding a dog cow's milk. Some vets may suggest hiding medication in cheeses, but will advise against giving a dog dairy milk. This mixed message is confusing, especially when trying to determine if milk is safe for dogs.
Canine Dietary Requirements
Dogs require a balanced diet to remain healthy. A dog is not a carnivore--meaning they solely need to eat meat--but instead are omnivores, meaning they need both meat and plants in their diet.
Although most people can enjoy and digest dairy products like milk or cheeses, dogs are not able to adequately break down and digest the majority of these foods. Like some people who are "lactose intolerant," dogs do not reliably produce enough lactase, the enzyme that breaks down milk sugars, to effectively digest most dairy products.
When a dog is unable to adequately break down milk sugars, or lactose, they will most commonly experience loose stools or diarrhoea. Other digestive reactions include vomiting or gas.
Lactose Content in Dairy Products
An understanding of the lactose content can help mitigate the digestive disruption a dog might experience when fed dairy products. Cow's milk contains approximately 11 grams of lactose per cup, whereas one ounce of cheddar cheese contains less than one gram.
Trial and Error
Because dogs do produce some lactase, they are able to digest some lactose. Since this enzyme is not produced in quantity, dog owners need to exercise caution in the dairy products they feed their dogs. Cow's milk contains a significant amount of lactose, so it is advisable to avoid feeding this to a dog. Beginning with low-lactose-content dairy products, like cheddar cheese, pet owners who want to feed their dog dairy can gauge the reaction and digestibility of these foods.