Comparison of <i>in vitro</i> Fermentation with <i>in situ</i> Degradation to Estimate Dry Matter Degradability and Energy Protein Synchronization of Roughage Based Diets

Abstract

This study was aimed to evaluate the correlation between <em>in vitro</em> fermentation and <em>in situ</em> degradation parameters and to predict dry matter degradability and energy protein synchronization of roughage based diets. Different inclusion of roughage in diets [roughage 50% diet (R₅₀D), roughage 60% diet (R₆₀D), roughage 65% diet (R₆₅D) and roughage 70% diet (R₇₀D)] were used to determine <em>in vitro</em> and <em>in situ</em> parameters. The relationships between <em>in vitro</em> and <em>in situ</em> parameters were analyzed by simple linear regression. The gas volumes and fermentation kinetics of R₅₀D and R₆₅D were greater (P<0.05) than those of other diets, however the lesser values of partitioning factor for microbial protein synthesis efficiency was found in R₅₀D. Although the nutrient disappearances, degradation kinetics and effective degradability were greater (P<0.05) in R₅₀D in compare with R₆₀D and R₆₅D, the lowest (P<0.05) energy protein synchronization was observed in R₅₀D. The significant correlation (P<0.05) were observed in all regression equations of <em>in vitro</em> gas volumes and <em>in situ</em> nutrient disappearances. The <em>in situ</em> effective dry matter degradability and energy protein synchronization were correlated (P<0.05) with <em>in vitro</em> fermentation kinetics and some estimated parameters such as short chain fatty acid and partitioning factor for microbial protein synthesis efficiency. Among the correlations, the greater accuracy could be achieved by inclusion of two or more parameters in regression equation. The results showed that <em>in vitro</em> gas production technique has the potential to predict effective dry matter degradability and energy protein synchronization of roughage based diets.