Oily fish are a great source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have anti-inflammatory effects and are beneficial in managing inflammatory joint and skin conditions. Whilst omega 3 fatty acids aren't recognised as an essential nutrient in a dog's diet, they are important for retinal and brain development, among others.
How much fish to feed?
Fish that is bought fresh needs to be frozen before feeding- you can read more about this here.
Fish and seafood is included in the 80% meat portion of a ratio diet, and should be fed as boneless meat in small quantities. The bones are small, soft and flexible, so there is no need to remove the bones but they don't contribute towards the 10% bone for this reason. There is no fixed quantity to feed, but aim to feed approximately a day's recommended intake in fish across the week. For example, if your dog eats 100g of raw a day, aim to feed 100g of oily fish over the week. This is equivalent to a whole raw mackerel or a tin of sardines in spring water.
There are some types of fish that are better to give than others. With raw fish, we are concerned about two things; mercury and thiaminase. Mercury is a heavy metal that concentrates in the flesh of fish, and is toxic to dogs. Large predatory fish have the highest amounts of mercury in their flesh, including shark, tuna, king mackerel and swordfish. Then we have thiaminase, which is an enzyme that inhibits absorption of the B vitamin thiamine. Thiaminase is only present in some species of fish, and is only a concern in raw fish as heat destroys the enzyme.
Safe to Feed
Atlantic Cod.
Atlantic Hake.
Atlantic Halibut.
Atlantic Mackerel.
Atlantic Salmon (preferably wild caught).
Haddock.
Lake Herring
Lake Trout.
Pollock.
Sprats.
Trout (all types).
Ones to Avoid
Anchovy.
Catfish.
Lake Whitefish.
Lobster.
Pacific Mackerel.
Sardine.
Sea Herring
Shark.
Smelt.
Tuna.
What about other seafood?
Mussels and Oysters are also good additions into the diet, with mussels being a rich source of manganese and oysters providing zinc. Both of these nutrients are often deficient in ratio diets. Both mussels and oysters are bivalve molluscs and may be contaminated with a type of toxic marine plankton, known as dinoflagellates. For this reason, molluscs must be served cooked and deshelled, so only the flesh is given. Oysters can be difficult to source in the UK, but deshelled and cooked mussels are available to by frozen and fresh in supermarkets such as Morrisons. These are super handy just to grab and add a few to meals for a nutritious boost.
Alternatives to fish
Tinned fish is a great alternative and may be enjoyed more by fussy dogs. As thiaminase is not a concern in cooked fish, most fish can be given. Popular options include sardines, mackerel and herring. Fish in spring water is preferred, but tomato sauce varieties can also be given with most of sauce removed. Brine should be avoided.
Fish body oils are very prone to oxidation and rancidification, while fish liver oils are high in vitamins A and D. Both should be avoided. If selecting an alternative fish oil, look at krill or algae oils.