In vitro techniques for the evaluation of ruminant feeds.

For the purposes of this symposium in vitro techniques for the evaluation of ruminant feeds are defined as laboratory methods in which the availability of nutrients in the feed to the digestive process in the ruminant animal is estimated by the incubation of the feed with micrwrganisms or semi-purified enzyme preparations, or both. Ewart (1974) reviewed for the Society recent developments in continuous in vitro rumen systems which are characterized by the continuous or intermittent removal of the products of fermentation and the feed residues. In batch in vitro systems, in contrast, there is no attempt to remove the feed residues and non-gaseous products of fermentation. In this review only batch in vitro methods will be examined as laboratory procedures for the estimation of the digestible (DE) or metabolizable (ME) energy contents of feeds and the metabolizable protein made available by diets.