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This study was performed to evaluate the effect of different feeding systems (choice feeding and conventional system) on performance and emission of carbon dioxide (CO2) and enteric methane (CH4) in dairy Awassi ewes. One chamber was equipped with gas analyzers to measure CH4 and CO2 for 23 h day-1. In total, 16 ewes were used. The ewes were divided into two groups: the Free Choice (FC) group received feed ingredients separately and the Total Mixed Ration (TMR) group received a standard mixed concentrate: forage diet in a ratio of 60:40. The results showed no significant differences between treatments in performance parameters. However, the results of CH4 and CO2 measurement indicated significant differences between groups in the amounts of CH4 and CO2 produced per kg dry matter intake. The ewes in the FC group produced less CH4 per animal than the ewes that received the TMR system. In ewes on the FC system, the level of propionate was greatly increased relative to the total VFA components. There were no significant differences in ruminal pH and acetate level between treatments. The results indicate that the FC system may be a potential mitigating effect on enteric emission of CH4 and CO2.
