It may likely just be that they're bored of the same 2 protein sources all the time. I know my cats looooooooove variety...... they eat probably a dozen different types of meat (everything from lamb to venison to wild boar and even kangaroo). I do feed them mostly commercial raw cause as a very busy vegan, it just makes the most sense for my situation. If you'd like to make your own with more exotic meats, try checking out farmer's markets or ethnic grocery stores. In some cases you may have to substitute another calcium source for bone, or feed a meal of chicken wings or necks every so often to make sure they kitties aren't eating too much muscle meat, but it should be doable.
Another tip would be to sprinkle the top of their meals with a 100% freeze-dried meat treat like PureBites or Whole Life. One of my cats is not a fan of kangaroo, but if that's what I've thawed out for the other cats' meals, that's what she's gonna get. I dust it with a liberal sprinkling of chicken or turkey powder and she almost always gobbles it down.
I'd have to advise against cooking any meals that were intended to be fed raw, like Dr. Pierson's recipe. Even if the bone is finely ground, it changes when cooked and would be less digestible, sharper, and more likely to cause a blockage. Plus the nutrient composition is altered. Would be better in that case to cook the muscle meat and organs separately and then add in everything else. Or you could get some Feline Instincts, which is a vitamin/mineral powder meant to be mixed with just raw muscle meat chunks.
Oh, one more thing: while the focus tends to be on canned tuna not being that great for cats, raw tuna should also be (mostly) avoided: http://catnutrition.wordpress.com/20...ding-for-cats/
Eight strikes against fishy feeding
So far, I count eight distinct ‘strikes’ against the idea of feeding fish, raw or cooked, to cats.
Strike One: Low calcium levels.
Whole fish, even with bone, is far too low in calcium for a cat. Remember: if you’re making homemade cat food, one of the most important things to get right is the ratio of calcium to phosphorus. You have some wiggle room here, but not much. A whole ground fish would be low in calcium. And while the high phosphorus is not good for any cat, elevated phosphorus levels are something you most definitely wouldn’t want to feed a cat that is suffering from any kind of kidney problem.
Strike Two: Thiamin destruction.
Raw fish contains high amounts of an enzyme called thiaminase–an enzyme that destroys Vitamin B-1 (thiamin). A thiamin-deficient diet can lead to neurological problems and seizures in cats. No good.
Strike Three: Urinary tract problems.
Fish, with its high magnesium content, can contribute to a type of urinary tract problem in cats.
Strike Four: Addiction.
Heaven knows, cats absolutely adore the taste of fish. Anyone who’s ever opened up a can of fish within a 12-city-block radius of any hungry feline knows that. But you can quickly end up with a ‘fish addict’ on your hands. And the last thing you need is a cat on a hunger strike refusing to eat anything but an inferior fish diet.
Strike Five: Heavy metals.
There is a great deal of persuasive research suggesting that predatory fish (those at the very top of the food chain and the same ones often found in pet food or used as ‘treats’ for cats) have extremely high levels of heavy metals such as mercury–in addition to pesticides and other toxins. A 2004 study published in Acta Neuropatholgica discovered neurological disturbances in young kittens fed tuna daily that contained the US FDA-approved level of mercury (0.5 ppm).
Strike Six: Possible link to hyperthyroidism.
A US Environmental Protection Agency (EPA) study in 2007 revealed a disturbing link between feline hyperthyroidism and the chemicals in fire retardants–that mimic thyroid hormones–and cats’ consumption of fish. In the study, cats eating canned fish were exposed to polybrominated diphenyl ethers (PBDEs) that were five times higher than cats eating poultry or beef canned foods.
Strike Seven: Vitamin E depletion.
Felines love tuna, but eating it long term can deplete a cat’s stores of vitamin E and create conditions that lead to an extraordinarily painful condition called steatitis, with symptoms such as hypersensitivity to touch and loss of appetite. Huuuuuge bummer for the cat and for you. You’ll find tuna in lots of cat foods for the very reason that it’s tasty to cats and draws them to the food. But it has nothing to do with healthy, safe, or necessary nutrition for cats.
Strike Eight? Allergenic.
Fish are allergenic. To my mind, it just makes little sense to feed something that is more likely to create a allergic reaction than something that isn’t.
Dr. Jean Hofve wisely advises against feeding fish and suggests that it be reserved as a very occasional and special treat–certainly no more than once a week.
If you’re really anxious to give your cat a treat once in awhile, go for something like small bits of dehydrated chicken liver or freeze-dried chicken hearts. But skip the fish. Feed something with fur or feathers, not fins. It’s kinder to–and safer for–your carnivore.
Now all that said, it probably wouldn't be a big deal if you mixed some raw tuna in very occasionally, but I think it would be a better idea to first find some other meats that your cats are interested in and rotate those around.
Hope that helps a bit!