Evaluation of nutritional value in some tropical by-products using the in vitro gas production technique

Abstract

Anaerobic digestion of carbohydrates by ruminal microbes produces short chain fatty acids (SCFA), CO2, CH4, and traces of H2; hence, measurement of gas production in vitro can be used to study the rate and extent of digestion of feedstuffs (Hungate, 1966). When a feedstuff is incubated with buffered rumen fluid in vitro, the carbohydrates are fermented to SCFA, gases mainly CO2 and CH4 and microbial cells. Gas production is basically the result of fermentation of carbohydrates to acetate, propionate and butyrate (Wolin, 1960; Beuvink and Spoelstra, 1992; Blummel and Ørskov, 1993). High correlations between gas production and NDF disappearance, r2 = 0.99 (Pell and Schofield, 1993) or gas production and DM disappearance, r2 = 0.95 (Prasad et al., 1994) have been reported. In vitro techniques that estimate digestion kinetics indirectly by measuring gas production are a more viable option than other in vitro methods. Gas production technology allows for a more usable collection of digestion kinetics data and has allowed for a growing body of knowledge that is directly applicable to the feeding programs that are in daily practical field use. The range of data that can be acquired is broad and will no doubt grow over time. One of the most challenging problems associated with using gas production methods is that the amount of gas produced varies with different molar proportions of SCFA. For example, a higher propionate concentration is associated with lower gas production because an extra carbon atom in propionate would otherwise have appeared as CO2 (Wolin, 1960). The object of this study was to evaluate the nutritional quality of noodle waste (NW), tomato pomace (TP) and apple pomace (AP) using the gas production technique.