A US magazine recently ran an article that included tuna on a list of 20 items you should never feed your pet. That same day a newspaper published a column written by the Humane Society that gave recipe ideas for dog treats. One of those recipes listed tuna as an ingredient.
The discrepancy prompted questions wanting to know which was correct.
The only danger associated with eating tuna is consumption of mercury, which is a chemical element used in thermometers, barometers and other scientific measuring devices.
These inorganic forms of mercury are converted to the organic forms methylmercury and ethylmercury by microorganisms in the sediment of rivers, lakes and seas.
Fish and shellfish absorb the most toxic form, methylmercury, and concentrate it in the brain, muscle and kidneys. Fish higher on the food chain, such as shark, swordfish, king mackerel, albacore tuna and tilefish, contain higher concentrations of mercury.
Shrimp, tilapia, salmon, pollock, catfish and canned light tuna historically contain relatively low levels of mercury.
Signs of mercury poisoning may include blindness, excitation, incoordination and convulsions. Cats may also exhibit hind leg rigidity.
These sings are seen after a latent period that may last for weeks. Unfortunately, once neurological signs present themselves, they are often irreversible.
The good news is that we almost never see this. In one report it took almost 11 months of feeding tuna multiple times a day for signs to be seen in a cat. In another report a cat was fed tuna exclusively for two years before any signs were observed.
Reports of mercury poisoning in dogs were somewhat obscure but seemed to parallel the findings in the cat.
Yes, feeding an all-tuna diet for the long term would be unwise and hazardous. But feeding a couple of frozen “pupcicles†(frozen dog treats containing tuna and yogurt) should not pose an imminent threat to any of our four-legged friends.