ORIGINAL ARTICLE

Abstract Understanding the effects of dietary composi-tion on methane (CH4) production of sheep can help us to understand grassland degradation resulting in an in-crease of CH4 emission from ruminant livestock and its resulting significance affecting CH4 source/sink in the grazing ecosystem. The objective of this study was to investigate the effect of forage composition in the diet of sheep in July and August on CH4 production by sheep in the Inner Mongolia steppe. The four diet treatments were: (1) Leymus chinensis and Cleistogenes squarrosa (LC), (2) Leymus chinensis, Cleistogenes squarrosa and concentrate supplementation (LCC), (3) Artemisia frig-ida and Cleistogenes squarrosa (AC), and (4) Artemisia frigida, Cleistogenes squarrosa and concentrate supple-mentation (ACC). CH4 production was significantly lower in July than in August (31.4 and 36.2 g per sheep-unit per day, respectively). The daily average CH4 pro-duction per unit of digestive dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) in-creased by 10.9, 11.2 and 42.1 % for the AC diet com-pared with the LC diet, respectively. Although concentrate supplementation in both the AC and LC diets increased total CH4 production per sheep per day, it improved sheep productivity and decreased CH4 production by 14.8, 12.5 and 14.8 % per unit of DM, OM and NDF digested by the sheep, respectively. Our results suggested that in degraded grassland CH4 emis-sion from sheep was increased and concentrate supple-mentation increased diet use efficiency. Sheep-grazing ecosystem seems to be a source of CH4 when the stocking rate is over 0.5 sheep-units ha1 during the growing season in the Inner Mongolia steppe