Dairy, Eggs and Fish: What Dogs Can Actually Have

Three categories that come up repeatedly, each with a bit more nuance than a simple yes or no.

Dairy

Most adult dogs are lactose intolerant to some degree.

Puppies produce lactase, the enzyme that digests milk sugar, in order to handle their mother’s milk. Production declines substantially after weaning, which is normal for a mammal. The result is that many adult dogs cannot digest lactose well, and it ferments in the gut, causing wind, loose stool and discomfort.

The degree varies considerably between individuals. Some dogs handle dairy perfectly well; others get diarrhoea from a teaspoon.

Lower-lactose options, which many dogs tolerate:

• Hard cheeses — cheddar, parmesan. Lactose is largely removed in the making
• Plain natural yoghurt, where bacteria have consumed some of the lactose
• Kefir, lower still
• Cottage cheese, in small amounts

Higher-lactose, more likely to cause problems: milk, cream, ice cream, soft cheeses.

The rules:

• Start with a teaspoon and see what happens
• Nothing sweetened. Check for xylitol, which is lethal to dogs — it appears in some yoghurts and ice creams
• Watch the calories. Cheese is very calorific and salty. Excellent as a high-value training reward in pea-sized pieces, bad as a daily habit
• Avoid in dogs with a history of pancreatitis, given the fat content
• Never cow’s milk for puppies. It is nutritionally wrong and causes diarrhoea. Use a proper puppy milk replacer

“Dog ice cream” and dog milk products are typically lactose-reduced and fine in moderation. They are also usually unnecessary — frozen plain yoghurt or frozen banana does the same job.

Eggs

Safe, nutritious, and genuinely useful — a complete protein with a good amino acid profile, plus B vitamins, selenium and choline.

Cooked, always. Two reasons:

1. Salmonella risk, for the dog and for the household. Dogs shed it in faeces and saliva
2. Avidin, a protein in raw egg white, binds biotin and can contribute to deficiency if raw eggs are fed in quantity over time. Cooking denatures it

The avidin issue is often overstated for an occasional egg, but combined with the salmonella point there is no good reason to feed raw.

How to serve: boiled, scrambled or poached, with no butter, oil, salt or seasoning.

Portion: a whole large egg is roughly 70 to 80 calories, which is a meaningful share of a small dog’s daily allowance. Half an egg for a small dog, one for a medium, two at most for a large dog, and not every day.

Eggshells are sometimes suggested as a calcium source. They are — but the calcium content is not precisely controlled, and adding calcium to a complete diet is a bad idea, particularly in a growing large-breed puppy where it causes skeletal disease. Do not do this without veterinary or nutritionist guidance.

Fish

Excellent for dogs, and the best natural source of the long-chain omega-3 fatty acids EPA and DHA, which have the strongest evidence of any supplement for joints and skin.

Good choices:

• Sardines in spring water, no added salt. Cheap, whole, and the small soft bones are safe and provide calcium
• Mackerel, similar
• Salmon, cooked thoroughly
• White fish — cod, coley, pollock. Very lean and easily digested, useful in a bland diet

Always cooked, with two exceptions to be aware of:

Salmon poisoning disease. In parts of the Pacific Northwest of North America, raw salmon and some other fish can carry a fluke harbouring a rickettsial organism that causes a severe and often fatal illness in dogs. Cooking kills it. If you are in that region, raw salmon is genuinely dangerous.

Thiaminase. Some raw fish species contain an enzyme that destroys thiamine (vitamin B1), and long-term feeding of raw fish can cause deficiency.

Bones. Small soft bones in tinned sardines are fine. Cooked fish bones from a fillet are not — they splinter. Remove bones from any fresh fish before serving.

Mercury. Large, long-lived predatory fish — tuna, swordfish, shark, king mackerel — accumulate mercury. Small oily fish are both safer and higher in omega-3. Tinned tuna occasionally is not a problem; it should not be a staple.

Portion: a quarter to half a tin of sardines for a medium dog, once or twice a week, counted within the treat allowance.

The rule that covers all three

Ten percent. Treats and extras of any kind, including all of the above, should stay under ten percent of daily calories, and should be subtracted from meals rather than added on top.

A complete and balanced food is formulated as a whole. Adding significant quantities of anything dilutes that balance, and the most common consequence is not deficiency — it is a fat dog.

Introducing anything new

One food at a time, in a small amount, so you know what caused a reaction.

And watch for the pattern where a dog who has been offered something tasty starts refusing their ordinary food. That is not fussiness developing; it is a dog making a rational decision based on the evidence you have given them.