A history ofin vitrotechniques

Abstract

AbstractRegressions relating in vivo digestibility to chemical composition of the food have residual standard deviations that are unacceptably high. The development of the two-stage in vitro technique inoculated with rumen liquor (Tilley and Terry, 1963) allowed dry-matter digestibility to be predicted with greater accuracy. This success was followed by a series of developments which replaced rumen liquor with inoculum produced from fresh or preserved faeces collected from sheep or cattle. Other methods used inoculum from a continuous fermentation containing rumen micro-organisms and enzymes produced by fungi. Another modification was to use gas production as a measure of in vitro digestion. The range of nutritional problems that could be measured by in vitro techniques was extended to include the estimation of voluntary food intake and protein degradation. All these in vitro techniques require standardization using food samples that have previously been analysed in vitro or offered as the sole diet to animals. The relative merits of these two calibration methods are discussed. Special facilities are required for storing and distributing these standard foods.