Effect of different concentrate diet levels on rumen fluid inoculum used for determination of in vitro rumen fermentation, methane concentration, and methanogen abundance and diversity

This study investigated the effects of different diet concentrate levels in animal diets as a source of rumen fluid inoculum for in vitro ruminal fermentation, CH4 concentration, and methanogen abundance and diversity. Three non-lactating mature cows assigned to a 3 x 3 Latin square design were fed with Italian rye grass and concentrate feed at 2 (low), 5 (medium), and 8 (high) kg per animal per day were used as rumen fluid donors. The experiment consisted of three 21-d periods that each consisted of 14 d adaptation followed by 7 d of continuous feeding prior to rumen fluid collection for in vitro fermentation evaluation. High concentrate proportion produced the highest total gas in all incubation periods (p < .05) while methane (CH4) concentration was highest in low concentrate proportions and lowest in medium concentrate proportions. Propionate concentration was highest in high concentrate proportions, whereas butyrate concentration was highest in medium concentrate proportions. High concentrate proportion at 0 and 12h and medium concentrate proportions at 12h produced archaeal denaturing gradient gel electrophoresis (DGGE) profiles that differed from those of low concentrate proportions. Medium concentrate proportion had the lowest methanogen DNA copies at 12h of incubation (p < .05). Changes in diet influenced the rumen microbiome, CH4 concentration, and methanogen diversity and abundance in cattle. The rumen conditions of an animal, as along with the microbiome, change as the feed diet changes. As a result, the inoculum for in vitro rumen fermentation studies affects Volatile fatty acid (VFA) concentrations, CH4 production, and methanogen diversity and abundance.