Stale food could harbour multiplying bacteria which can cause food poisoning. Stale food may also have visible fly eggs on it. Always rinse the bowls well after dish-washing. Even the most undemanding cat may dislike one particular flavour or texture. Faddy cats, however, dislike MOST flavours.
Cats soon learn to avoid their normal food after only a few days of finding medicine in it.
The cat's sense of taste is so good that medication odourless to humans is detectable to cats. Try putting medication in a smelly 'treat' food such as pilchard or strong cheese, and vary the treats. Stale Food . The food might be 'off' - tinned food left open on the shelf will go stale. The box may fit neatly beside the washing powder, but cats don't like Persil-flavoured biscuit.