Pretty strange sentence. Cats are obligate carnivores because they require an amino acid called taurine to live, which is only found in animal protein. They will literally die without it. Maybe they are referring to raw meat in the sentence :P
I bet there are people that insist their cats are vegans (though as you pointed out, not for very long).
My cat preferred fish...
yes, but what is the sentence order with adverbs? Do they have to go in a certain place? I placed "rzadko" at the end and was told this was wrong.
Yeah, it doesn't sound like a natural word order. It is probably safest to put them directly before the thing the word they refer to, so "rzadko je".
Jest mi trochę niespokojnie na sercu po tym zdaniu.