Can dogs drink milk?

The detail

Puppies cope with milk because they make lactase, the enzyme that splits lactose into sugars the gut can absorb. Production drops off after weaning, so an adult dog handles a saucer of milk far worse than the puppy it used to be.

The lactose that goes undigested carries on into the large intestine and ferments there. That is where the wind, the gurgling and the soft stool the following morning come from.

Whole milk adds about 3.6g of fat per 100ml on top, which matters for dogs that have had pancreatitis. Semi-skimmed and skimmed cut the fat and keep the lactose, so they fix the smaller half of the problem.

There is also nothing in milk a dog needs. A complete dog food already covers the calcium, the protein and the B vitamins, so the only thing milk adds is a digestive gamble.

Can dogs drink cow's milk?

This is the version most dogs get offered, and the answer is that a splash is not poison but a bowl is a mistake. Most adult dogs make very little lactase, so the sugar in the milk goes undigested.

A cereal bowl's worth for a small dog usually means a soft stool within a day. A mug of it can mean vomiting and a night of getting up to let your dog out.

If your dog has drunk a lot, leave fresh water down and skip the next meal if the stomach is unsettled. Ring your vet if the diarrhoea runs past a day or two, sooner for a puppy or a small dog.

Lactose-free milk

Lactose-free milk takes out the part most dogs struggle with, so it goes down better and is less likely to end in loose stools. It is otherwise still cow's milk: the same fat, the same calories, the same absence of anything your dog is short of.

Better tolerated is not the same as needed. If you give it at all, treat it as a treat with a size limit rather than a drink, and keep water as the thing in the bowl.

Puppies and cow's milk

Cow's milk is not a substitute for a proper puppy milk replacer. The PDSA's hand-rearing guidance says plainly that cow's milk is unsuitable and that newborn puppies need an artificial formula made for puppies, and it rules out the kitten and puppy milk drinks sold in supermarkets too.

If you are hand-rearing orphan puppies, ring a vet the same day. Feeding volume, feeding frequency, keeping the litter warm and helping them toilet all matter in the first weeks, and there is no way to work that out from a shopping list.

Weaned puppies sit in the same place as adults. A saucer of cow's milk is a stomach upset waiting to happen, and a puppy has less body weight to absorb it.

Oat, almond and soy milk

Plant milks are not toxic to dogs, and they are also unnecessary. They bring calories and sugar to a diet that already covers everything, and nut milks bring fat with them.

Sweetened cartons are the ones to check. Anything labelled sugar-free may be sweetened with xylitol, which causes a life-threatening drop in blood sugar in dogs and can cause liver failure, so read the ingredients before a drop goes near a bowl.

Soy is worth a second thought as well. VCA Animal Hospitals lists soy among the proteins that most often cause food allergy in dogs, alongside dairy, beef, chicken, egg and wheat gluten.

Milk in tea and the leftover cereal bowl

The PDSA is clear that adding milk to tea does not make tea safer for a dog and makes it worse, because the milk upsets the stomach on top of the caffeine. Tea stays yours.

Cereal leftovers are the commonest route in around a UK kitchen. A bowl of milky Weetabix left within reach is the classic version, and the milk causes more trouble than the biscuit does.

Put bowls straight in the sink rather than on the coffee table. That one habit removes most of the milk a dog ever drinks.