Use of Laboratory Methods to Estimate the Performance of Beef Cattle Fed Mixed Rations Containing Silage

Thirty rations containing silage and other feed constituents were used in feedlot trials, in vivo digestion trials and laboratory evaluations (Tilley and Terry, 1963, in vitro DDM; Van Soest, 1963, acid insoluble lignin; Dehority and Johnson, 1964, dry matter solubility) to determine if these laboratory procedures could be used to estimate average daily gains (ADG) and Voluntary Intake (VI) by beef cattle. Highly significant (P<.01) correlations of in vivo digestible dry matter (DDM), digestible organic matter, total digestible nutrients (TDN), digestible energy with in vitro DDM or acid insoluble lignin were obtained. Correlations between in vivo digestibility and dry matter solubility of the ration were much smaller. Correlations between ADG and in vitro DDM or acid insoluble lignin were significant (0.01 <P<0.05), but a small nonsignificant correlation was obtained for ADG and dry matter solubility of the ration. Correlations obtained between the laboratory evaluations and TDN intake above maintenance, the four measures of nutritive value index or the three measures of VI were significant (0.01<P<0.05).