Effect of spices on rumen fermentation, methanogenesis and protozoa counts in in vitro gas production test

Abstract

The effects of water, methanol and ethanol extracts of Foeniculum vulgare (fennel), Syzygium aromaticum (clove), Allium sativum (garlic), Allium cepa (onion) and Zingiber officinalis (ginger) on rumen fermentation, methanogenesis and ciliate protozoa counts were studied in in vitro gas production test. Gas production was reduced ( P < 0.05) on addition of ethanol and methanol extracts of fennel and clove. Water extract of garlic and all the three extracts of onion caused higher ( P < 0.05) gas production. Ethanol and methanol extracts of cloves and garlic and methanol extract of fennel inhibited ( P < 0.05) methane production. However, water extracts of these products and all extracts of onion and ginger had no effect on methane production. Total volatile fatty acids were higher ( P < 0.05) in the medium on inclusion of extracts of garlic and onion. All extracts of garlic and methanol extract of fennel caused a decrease in molar proportion of acetate and acetate to propionate ratio. Methanol and ethanol extracts of clove decreased dry matter degradability (DMD). The ethanol and methanol extracts of clove caused a decrease ( P < 0.05) while extracts of onion, ginger and garlic caused an increase ( P < 0.05) in protozoa numbers. Plant secondary metabolites extracted in ethanol and methanol from garlic appear to have a potential to reduce rumen methanogenesis without affecting rumen fermentation adversely.