Unfortunately the problem with the feline diet goes well beyond wheat gluten in cat food, mentioned by Deborah Duchon yesterday in "The Best Cat Food." These days some people are trying to place dogs and cats on a vegetarian diet because they themselves have eschewed meat as part of the human diet.
Sometimes these people act out of misguided compassion but often they are trying to make a political statement. A search on the term 'vegetarian diet cats' will bring up many sites that urge people to place their "companion animals" on vegetarian and vegan diets. Some even claim such an action will lengthen the animals' lives. Unfortunately cats will sicken, can go permanently blind and may even die on such fare unless a great deal of care is taken to provide additional nutrients, particularly vitamin A, which cats cannot synthesize from carotene as people and dogs do, taurine and arachidonic acid.
Dogs are more omnivorous by design than cats, so they are less likely to become ill from misguided owners who try to turn them into vegetarians. That does not mean that many dogs like the idea, however. The vegetarians on the other side of my valley tried to feed their dogs such a diet only to find their springer spaniel, Livy, was always inviting herself over to share my dog Clare's supper. Livy would also hang out around the local campground where she was known to retrieve entire chickens and steaks off of the grills. I was calling them to come pick Livy up two or three times a week. Between the high price of vegetarian dog food, their dogs constantly dragging animal bones out of the woods and Livy's making a general nuisance of herself they switched back to less esoteric fare for their pets.
I am all with Deborah. I leave just enough commercial food out for my cat to keep her hanging around. It is a brave mouse indeed that has ventured into my house since both a hungry cat and an inquisitive Jack Russell terrier took up permanent residence. Deborah omitted, however, that it may not be a good idea to let your cat hunt if you are prone to heart attacks. My cat, Lucille, has almost scared the life out of me several times when I've walked in and turned on the lights only to have a panic-stricken bird explode into the air. It seems she prefers to confine birds indoors and play with them for a while before they become her dinner. Many are the times when I must call on Clare the terrier to perform the coup de grace on one of Lucille's catches. Personally I have always been amused by those who say only man kills for fun. They have obviously never watched a domestic cat at work