A review of a few key factors regulating voluntary feed intake in ruminants

During the history of ruminant nutrition many factors have been proposed as regulators of voluntary feed intake. In some cases, the implicit assumption has been that a factor acted independently and exclusively of other mechanisms. A knowledge of ruminant digestive anatomy aids in understanding both the ecological niche and the feeding behavior of the ruminant animal. Factors controlling ruminant intake should be assumed to function with multiple interactions. A number of feedback regulators such as distension, protein, and energy should be considered in the context of their interacting regulatory effects when attempting to predict intake. Behavioral aspects also influence voluntary feed intake through associations formed via post-ingestive feedback. Ruminants can learn to identify particular feeds and alter intake on the basis of past experiences. An integrated approach is proposed as a means of understanding ruminant feed intake regulation and eventually to improving prediction of intake. Empirical mathematical methods are likely to be fundamental to developing understanding and models of feed intake because of the difficulty of studying the central nervous system. In spite of these difficulties, knowledge of theoretical feedbacks has already been used to develop practical ruminant feeding strategies.