Cod liver oil in a capsule, which is the format that exists because the alternative is a bottle of fish oil and a spoon. Johnson's list it for dogs and cats and also for cage birds and pigeons, which is a wider species range than most supplements claim and tells you this is an old, plain product rather than a formulated one.

The composition is cod liver oil, and that is the whole of it. Johnson's describe it as a natural conditioner and dietary supplement providing vitamins A, D and E. They name the three vitamins and give no figure for any of them. The capsules come in three sizes across the range, from a small carton to a very large one, and the larger pack sizes moved out of a plastic tub into a recyclable carton as part of the company's plastic reduction policy.

* Composition: cod liver oil * Supplies vitamins A, D and E * Listed for dogs, cats, cage birds and pigeons * Sold in 40, 170 and 800 capsule packs * Larger packs now in recyclable cartons rather than plastic tubs

Vitamins A and D are fat soluble, and this pack gives you no numbers to work with. Water soluble vitamins are forgiving of a rough guess and these two are not: they are stored rather than passed. Johnson's publish no quantity per capsule and no feeding amount on their site, and they publish no analytical panel for anything in their range, so there is nothing on the label to reconcile against another supplement you may already be giving. If your animal is on anything else containing vitamin A or D, that is a question for your vet rather than for us.

Who it's for: Owners who want a single-ingredient oil supplement in a capsule, and who are either taking the vet's steer on how much to give or already know what they are doing.