I'm curious what you guys think about feeding your cat tuna or salmon, either straight or as a main ingredient in cat food.
Humans are warned not to eat too much salmon and tuna due to the toxins in them. I've heard that various health organizations recommend humans eat salmon no more than 3 or 4 times a month -- so I imagine the risk to a small animal like a cat would be even greater.
For those of you may not know about toxicity in fish, the reasoning is that any fish that are carnivorous have increased toxicity due to the fact that they accumulate all the toxins in the smaller fish that they eat. All animals high in the food chain are susceptible to this.
Is this something we should worry aboutfor our kitties?
Unsu...Well...I know if I eat too much tuna I get sick. I love tuna melts but only eat them a couple times a year. My cats love tuna too. On the occasions I have a tuna melt, they get a little taste too. Their normal everday food is Max Cat dry. I'm not sure but I think it's fish free. I've heard from lots of sources that it's just bad for cats.
I wrote a looooong thing about Feline Issues with Fish on the Feline Nutrition tribe (shameless plug). It's buried in this thread here: www.tribe.net/tribe/servl...iewThread.vm . But I'm excerpting what I wrote on fish below; it includes information on feeding raw fish to cats if you're into that kind of thing. Also, the warnings about vitamin E don't apply to "complete" cat foods containing fish, only to meals served to kitty consisting mostly of fish.
Fish is a rather sticky issue. First of all, fish isn't inherently BAD for cats, especially if you're talking about small, fresh, wild-caught fish. But many types of fish are problematic for cats. Tuna, for example, is notorious for being extremely addictive and for depleting the cat's vitamin E stores. Cats fed a lot of tuna (or any other fatty fish with a high polyunsaturated fat content) without vitamin E supplementation can eventually get steatitis or yellow fat disease, a condition caused by the body's fat tissue being attacked by free radicals because they're left without the protection vitamin E offers.
Fish is also subject to contamination from various sources. Mercury content in tuna is a pretty legitimate concern, for example. And various toxins and pesticides often wash out into the ocean, are consumed by little fishies, build up in their fatty tissues and become more concentrated as they move up the food chain. Fish high up in the food chain can often contain a startlingly high amount of organochlorides.... Also, most types of farmed fish are Very Bad For You. They're the aquatic equivalents of feedlot cattle and chickens, fed shitty, additive-laden food in dirty, crowded conditions swarming with parasites. And artificial coloring is actually added to farmed salmon to give them that orangey-pink color we're used to, because the deficient diet fed to farmed salmon leaves their flesh grey (the pink hue in wild salmon comes from eating a diet rich in little shrimpies).
Certain types of raw fish also contain an enzyme called thiaminase, which interferes with the absorption of thiamin, a B vitamin. Thiaminase is deactivated by heat (but so's thiamin, hahaha), so with cooked fish it isn't an issue. However, thiaminase isn't present in all kinds of fish. This webpage here contains a table listing various species that contain thiaminase as well as a list of fish that DOESN'T: print.nap.edu/pdf/0309033...image/64.pdf and print.nap.edu/pdf/0309033...image/65.pdf . A little bit more info found here: www.gov.ns.ca/nsaf/elibra...feedherr.htm : "In addition to herring, thiaminase enzyme is found in capelin, suckers, smelts and various carp species, a total of some 50 species, most of which live in fresh water. For occurrence of thiaminase in fish see NRC, Nutrient Requirements for Mink and Foxes. Thiaminase activity is high in the viscera of the fish, but is rarely found in the muscle."
Noises have been made in the past about the mineral (ash) content of fish, and how it might contribute to urinary crystals, but it seems like the dehydration brought on by dry-food only diets might be the biggest contributing factor of all. Cooked fish also seems more of an issue than raw, which sort of makes sense, since meat loses water as it's cooked, and there may also be issues with the cooked protein being less acidifying to the urine than the raw (but this is me talking out of my ass now and speculating wildly). If your cat has had issues with crystals, I'd say avoid fish just to be safe.
So I wouldn't NOT feed fish, I'd just feed fish with caution. Choose fish from clean waters and preferably caught using sustainable methods, supplement with vitamin E (200-400 IU a week is plenty), and don't feed raw fish from the list of thiaminase-containing species.
This is a different post in the same thread about the use of ethoxyquin to preserve fish meal in pet food:
Ethoxyquin, another common preservative in commercial pet food, was originally developed by Monsanto as a pesticide and then later utilized as a rubber stabilizer. Now it's used as a potent fat preservative, and also in certain herbs and spices to keep the color vibrant (e.g. in paprika). It's sometimes "hidden" because by law, pet food companies only need to list on their labels what they add at their plant. If they buy fish meal from a supplier that's been treated with ethoxyquin, they don't need to list the ingredient on the bag since technically they didn't add it. If you're concerned, you should call the pet food manufacturer when you see foods that include fish meal and ask them to verify that they use only ethoxyquin-free fish meal.