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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Arthritis, or more properly, osteoarthritis in pets generally conjures up the image of the "creaky"old Labrador or German Shepard mix getting up slowly and walking painfully to the food dish. In fact cats are subject to this same aging process. Studies indicate an incidence of 22-72 percent of cats over six years of age for this condition. The joints of the spine, elbows, hips, shoulders and tarsi (ankle) are the most commonly affected.

Because cats tend to adapt their mobility to avoid pain, owners often find it difficult to identify these changes. Behavior changes like decreased activity, less grooming, or defecating outside the litter box may be mistaken for generalized ageing rather than early signs of osteoarthritis. Supplementing Omega-3 rich fish oils for osteoarthritis in dogs is now a common, successful veterinary recommendation. A recent study from Utrecht University in the Netherlands suggests that adding fish oil to the diet of cats with osteoarthritis has the same benefits.

The Fish Oil Study

Twenty-one cats with confirmed osteoarthritis participated in the 20 week study along with their owners. The cats were taken off any pain medications or supplements two weeks prior to the study. A dry food diet was supplemented either with Oil A: corn oil that had a fish odor but contained no omega-3, EPA, or DHA fatty acids; or Oil B: fish oil containing the omega-3, EPA, and DHA.

The cats were randomly chosen to start with Oil A or B and fed this diet for ten weeks. Owners completed an activity survey at the end of the two week medication and supplement “washout” period and at the end of each ten week oil treatment. Owners and experimenters were unaware of which oil the cats were receiving during their treatment periods. The survey results indicated that the cats had higher levels of activity, walked up and down stairs more, were less stiff, interacted more with the owners, and jumped higher when they received fish oil compared to the corn oil. Interestingly, the behavior during play, jumping on objects and grooming time improved with both oils with no significant statistical difference between the two treatments. The researchers attributed this finding to the placebo effect and/or the better care effect on owner perception.

Overall, the study makes a compelling case for supplementing osteoarthritic cats with omega- 3 fatty acids, specifically EPA and DHA.

Fish Oil — The Best Source for Fatty Acids

The EPA (eicosapentaenoic acid) and DHA (docahexaenoic acid) are the long chain omega-3 fatty acids known to reduce inflammation in humans and pets. These fatty acids are found preformed in fish oil. Seed oils like flaxseed and canola do not contain preformed EPA or DHA and require the body to convert other omega-3 fats to EPA and DHA.

Absorption and conversion of omega-3 fats is extremely variable with age, sex and health. In fact, studies in dogs indicate the omega-3 fats in seed oils are converted to EPA and DHP, a precursor to DHA. Because DHP is converted to DHA primarily in nerve tissue the levels of conversion are unknown. It has been found that one-third of cats older than six years of age have diminished ability to digest fats. By using a rich source of preformed EPA and DHA digestibility, absorption and conversion uncertainties are avoided.

The National Research Council has established a safe upper limit for EPA and DHA in the cat diet, so supplementation should not be unrestricted. Consult your veterinarian for a proper dosage.

Avoid fish oils that contain Vitamin D. Most fish liver oil products, although rich in preformed EPA and DHA, contain levels of Vitamin D that far exceed the daily safe upper limit for this vitamin in cats and dogs. Bone disorders and kidney and other soft tissue mineralization can result with excessive intake of Vitamin D.

Dr. Ken Tudor

Image: David Fisher / via Flickr

Comments  5

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  • Oils to use.
    01/31/2013 02:40pm

    Great topic, Dr. Tudor. The type of oils used do make such an important difference in quality of health for our pets.

    For starters, I am not sure about dogs, but know that cats have very limited D6D enzymes needed to process plant based materials, so just can't be good sources for our felines. (http://www.ncbi.nlm.nih.gov/pubmed/2519853)

    As for the type of oil used, I find that nutritiondata.com is a great site for checking nutrients found in ingredients, raw or cooked:
    http://nutritiondata.self.com/foods-fish%20oil000000000000000000000.html I personally would have expected that surface feeding fish would be worse for the Vitamin D content than bottom feeders, but upon researching find that menhadin oil that doesn't contain heavy metals is great according to the nutritiondata.com site, and cod liver oil is extremely bad for our pets, having way too much Vitamin D.

  • Vitamin D
    01/31/2013 06:26pm

    It's my understanding that one of the side effects of excess Vitamin D in cats can cause hypercalcemia. It was one of the things the doctor was assessing when we were afraid one of my herd was heading toward being hypercalcemic.

    Re: Osteoarthritis in cats

    Changes in behavior may be very gradual and difficult for someone to notice when they see the kitty on a daily basis. Dr. Tudor, do you have any suggestions for specific things to look for so an owner might be able to see the problem before it gets to being a painful problem?

  • theOldBroad
    02/01/2013 11:53am

    Your right. It is the hypercalcemia caused by hypervitaminosis D that creates all the problems.
    As I mentioned in the article, early signs of osteoarthritis are very non-specific in the cat. Decreased activity and decreased grooming can result from many conditions that afflict cats. Also cats, unlike dogs, mask ambulatory difficulty early in joint disease. As cats age it is common for veterinarians to recommend annual blood work and urinalysis. You might encourage your vet to add x-rays yearly or every other year for any of your cats over 8 years of age. This may pick up early degenerative changes in the spine and major joints so treatment can be initiated earlier. Certainly the addition of fish oil to their diets will certainly help.
    Dr. T.

  • 02/01/2013 02:10pm

    We have also found that green lipped mussel has seemed to improve activity level in both elderly dogs and cats as well.

  • 02/01/2013 06:25pm

    Taking x-rays as part of a senior checkup is a great idea. (Can we really call them x-rays or radiographs if they're digital?) I'll bring it up to the doctor the next time one of the critters has a checkup.

    Thanks so much, Dr. Tudor!

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