Which of the following is NOT mentioned as a type of complete feed in pellet form?

Complete feeds in pellet form are designed to provide all the necessary nutrients for horses in a convenient format. Typically, these feeds include a variety of ingredients that could be classified as whole grains, forages, and vitamins and minerals.

In this context, carrots, turnips, and cabbage leaves are all recognized as types of fibrous plant materials that can be processed into pellet form and included in such feeds. They provide important nutritional benefits, including vitamins, minerals, and fiber, which contribute to a horse's overall diet.

Rugby balls, on the other hand, do not belong to the category of edible or nutritional components for horses. They are not a food source and do not have any place in a discussion about complete feeds or nutritional feed types. This makes it clear that rugby balls are not appropriate nor relevant in the context of this question regarding complete feed ingredients.