If you have a middle aged to older dog or cat, then likely they have some degree of joint
They should be on a high quality, effective essential fatty acid (EFA).
There are a number of studies backing this up.
A study conducted last year in the Netherlands suggests that cats with naturally occurring osteoarthritis show symptom improvement when their diets are supplemented with omega-3 fatty acids.(1)
A Canadian study published last year that indicates that dogs with osteoarthritis, benefit for EFA supplementing.The dogs were fed a veterinary prescription diet containing high levels of omega-3 fatty acids from fish, and showed significant improvement in locomotor disability (problems moving around) and performance of daily activities.(2)
Fish, plant, and nut oils are the primary dietary source of omega-3 fatty acids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in cold water fish such as salmon, mackerel, halibut, sardines, tuna, and herring. ALA is found in flaxseeds, flaxseed oil, canola (rapeseed) oil, soybeans, soybean oil, pumpkin seeds, pumpkin seed oil, purslane, perilla seed oil, walnuts, and walnut oil. The health effects of omega-3 fatty acids come mostly from EPA and DHA. ALA from flax and other vegetarian sources needs to be converted in the body to EPA and DHA. Many people do not make these conversions very effectively, however.
This remains an ongoing debate in the nutrition community; fish and sea vegetable sources of EPA and DHA versus vegetarian sources of ALA. Other sources of omega-3 fatty acids include sea life such as krill and algae.
Both EPA and DHA can be taken in the form of fish oil capsules. Flaxseed, flaxseed oil, fish, and krill oils should be kept refrigerated. Whole flaxseeds must be ground within 24 hours of use, so the ingredients stay active. Flaxseeds are also available in ground
form in a special mylar package so the components in the flaxseeds stay active.
Be sure to buy omega-3 fatty acid supplements made by established companies who certify that their products are free of heavy metals such as mercury, lead, and cadmium.
Source: Omega-3 fatty acids | University of Maryland Medical Center
Dosing for fish oil supplements should be based on the amount of EPA and DHA, not on the total amount of fish oil. Supplements vary in the amounts and ratios of EPA and DHA. A common amount of omega-3 fatty acids in fish oil capsules is 0.18 grams (180 mg) of EPA and 0.12 grams (120 mg) of DHA. Different types of fish contain variable amounts of
omega-3 fatty acids, and different types of nuts or oil contain variable amounts of ALA.
Dogs- standard dose is 1000mg of fish oil/10lbs daily
Cats- standard dose is 1000mg of fish oil/10lbs daily
Dogs- 1 teaspoon ( 5ml) per 15lbs daily, 1 tablespoon per 50lbs daily
Cats – 1 teaspoon (5ml) per 10lbs daily