"Quite simply, most dried pet foods would have a low palatability without the use of flavourings - that is, your pet wouldn't eat them quite as enthusiastically. Digest is a flavouring or palatability enhancer which is often sprayed onto the kibble in small amounts to make the food more appetizing. There's nothing intrinsically wrong with it as an ingredient, and as long as the rest of the ingredients together make a complete and nutritious food then it can be thought of as spraying on a little bit of gravy."
Nowt wrong with a bit of gravy