337 *Corresponding author: bhatt_rs@yahoo.com In Vitro Ruminal Degradability, Fermentation Metabolites and Methanogenesis of Different Crop Residues R.S. Bhatt*, A.R. Agrawal and A. Sahoo Division of Animal Nutrition Central Sheep and Wool Research Institute, Avikanagar-304 501, India (Received September 09, 2013) ABSTRACT Bhatt, R.S., Agrawal, A.R. and Sahoo, A. 2014. In vitro ruminal degradability, fermentation metabolites and methanogenesis of different crop residues. Animal Nutrition and Feed Technology, 14: 337-348. In vitro rumen fermentation study of different source of crop residues used for livestock feeding in semi-arid region was conducted to compare the effects on degradability, fermentation metabolites and methanogenesis. Cereal crop residues (CCR) included pearl millet, barley, sorghum and wheat; leguminous crop residues (LCR) were chick pea, groundnut, and clusterbean; oilseed crop residues (OCR) were sesamum, and mustard; and spices crop residues (SCR) was cumin and fennel. The samples were incubated with ruminal buffer in glass syringes under anaerobic conditions for assessing the ruminal fermentation attributes. The degradability and methanogenesis parameters were assessed at t 1/2 (h), being determined following fermentation kinetic study of the crop residues. The CP content (g/kg DM) in legumes crop residues (80.6-194) was higher (P<0.05) followed by sorghum (67.9) and mustard (62.5) and was lower in other crop residues. Whereas the NDF was lower (P<0.05) in legume and spices crop residues compared to oilseed and cereal crop residues. LCR produced highest and SCR lowest (P<0.05) cumulative gas at t 1/2 (h). Pearl millet, cumin and groundnut crop residues produced lowest whereas sesamum and mustard crop residues produced highest methane at t 1/2 (h). The OCR had lower DM digestibility and highest methane per unit digestible DM. Total volatile fatty acids production was higher in fermented substrate of clusterbean, groundnut, sorghum, and wheat having higher proportion of propionate. Above all, pearlmillet, cumin and groundnut crop residues produced less CH 4 without compromising digestion and thus feeding of these crop residues could be a strategy to reduce CH 4 emissions. Key words: Crop residues, In vitro ruminal degradability, Metabolites, Methanogenesis. INTRODUCTION In arid and semi-arid region, ruminants survive mostly on low quality crop residues during most part of the year due to scarce grazing resources, scanty vegetation and unavailability of pasture during poor rainfall or drought. These feed resources although very important for sustenance of livestock are characterized by low nutritive Animal Nutrition and Feed Technology (2014) 14: 337-348 doi: 10.5958/0974-181X.2014.01333.X