Prediction of Silage Digestibility and Intake by Chemical Analyses or In Vitro Fermentation Techniques

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Abstract
Chemical analyses and in vitro fermentations were on 3 corn silages, 4 legume-grass silages and 4 corn-hay crop silage mixtures which were fed to sheep for 21 days. In vivo data were collected for voluntary silage intake and apparent digestibility of energy. Forage nutritive value was expressed as digestible energy intake. Multiple regression equations were developed to determine the more reliable methods to evaluate voluntary intake, digestibility and nutritive value of silage. Equations for quadratic response surfaces accounted for 71-79% of variation in in vivo data compared to 54-70% of variability accountable by simple linear regression equations. Dry matter, crude protein, cell wall, acid-detergent fiber and acid-detergent lignin contents of silage accounted for greater variability of silage intake, digestibility and nutritive value than did any in vitro method alone or in combination with chemical analysis. The nutritive value index expressed in the relative feed value system proposed by the American Forage and Grassland Council for differences between forages was supported.