Effect of supplements of yeast (Saccharomyces cerevisiae), rice distillers’ by-product and fermented cassava root on methane production in an in vitro rumen incubation of ensiled cassava root, urea and cassava leaf meal

摘要

An in vitro rumen incubation was carried out to determine effects on methane production of supplementing ensiled cassava root, urea and cassava leaf meal with rice distillers’ byproduct, fermented cassava root and yeast (Saccharomyces cerevisiae). The four treatments in a completely randomized design were: CTL: No supplement; RDB: 4% (in DM) rice distillers’ byproduct; FCR: 4% (in DM) urea-fermented cassava root; Yeast: 1% (in DM) commercial yeast. The quantity of substrate in each fermentation bottle was 12g DM to which were added 240 ml of rumen fluid (from slaughtered cattle) and 960 ml of buffer solution. The incubations were done using one-liter “PEP” bottles with gas collection by water displacement. Measurements of total gas production and methane percentage in the gas were made at intervals of 0-3, 3-6, 6-12, 12-18 and 18-24h. The hourly rate of gas production increased to a maximum in the 3-6h of incubation interval and then decreased linearly. In contrast, the proportion of methane in the gas increased linearly with incubation interval from the beginning until the final 18-24h interval. Total gas production was highest for the fermented cassava root additive, followed by the rice distillers’ byproduct with lowest values for the control and yeast treatments. The methane content of the gas was highest for the control treatment, followed by the fermented cassava root and yeast with the lowest value for rice distillers’ byproduct, for which the overall reduction in methane was of the order of 25%.  Methane production per unit DM digested showed a similar trend as the methane percentage in the gas. It is suggested that the benefits from brewers’ grains and rice distillers’ byproduct, in reducing methane production in the rumen fermentation, both in vitro and in vivo, are the indirect effects of these additives increasing the proportions of propionic acid in the rumen VFA.