A technique involving the measurement of the gas production from the microbial fermentation of a specified substrate in sealed conditions has recently been proposed as a method of assessing the fermentation kinetics of tropical feeds (Theodorou et al, 1992). In this technique the feed under test is the sole source of nutrients to the microbes and therefore it is possible that the nutrient release profile may have an influence on the microbial population leading to a modified gas production profile. The objective of this study was to investigate the effect of previous microbial experience on gas production.

One gram air dried feed samples were placed with 95 ml of modified van Soest media and 5 ml of strained rumen liquor in 150 ml serum bottles and sealed under anaerobic conditions. The rumen liquor was obtained from fistulated yearling wethers fed a maintenance diet of 0.9 good hay: 0.1 commercial 16% CP compound feed). Four replicates of fish meal (FM) and eight of spring barley grain (SPB) were set up together with control blanks.