The noun appetite can be countable or uncountable. In more general, commonly used, contexts, the plural form will also be appetite. However, in more specific contexts, the plural form can also be appetites e.g. in reference to various types of appetites or a collection of appetites.

What is the verb of appetite?

appetise. (rare) To whet the appetite.

What is the plural of feeding?

The plural form of feeding is feedings.