Environmental impact of yeast and exogenous xylanase on mitigating carbon dioxide and enteric methane production in ruminants

This study was carried out to establish Saccharomyces cerevisiae, xylanase, and their mixture as environmentally friendly feed additives that can reduce enteric biogas production. Rumen liquor was obtained from two rumen cannulated Holstein steers, two rumen cannulated Creole goats and two rumen cannulated Rambouillet sheep. The basal ration was supplemented (per g dry matter (DM)) with 2 mL xylanase, 4 mg S. cerevisiae or a mixture of both additives. There was no interaction (P > 0.05) between inoculum source and additive type. Inclusion of additives resulted in higher (P = 0.045) asymptotic gas production (GP) with sheep inoculum. Furthermore, higher (P < 0.05) GP rates with goat and sheep inocula were noted with the additives. S. cerevisiae or/and xylanase decreased (P < 0.05) proportional methane (CH4) irrespective of the inoculum source with an increase (P < 0.05) in carbon dioxide production. Higher (P < 0.05) bacterial counts were observed with the inclusion of the additives. Metabolizable energy and short fatty acid concentrations were higher (P < 0.05) when the additives were supplemented to goat and sheep inocula. Additionally, inclusion of the additives resulted in higher (P < 0.05) DM degradability in sheep and steer inocula and higher (P < 0.05) organic matter degradability in goat and sheep inocula. S. cerevisiae, xylanase and their mixture did not affect total GP but altered the proportion of the gases generated. Furthermore, CH4 production was reduced in the presence of the additives. Thus, the additives can be utilized in an environmentally friendly and sustainable way to reduce biogas emissions from livestock; thereby improving environmental conditions. (C) 2018 Elsevier Ltd. All rights reserved.