Effects of forage composition and growing season on methane emission from sheep in the Inner Mongolia steppe of China

Understanding the effects of dietary composition on methane (CH 4 ) production of sheep can help us to understand grassland degradation resulting in an increase of CH 4 emission from ruminant livestock and its resulting significance affecting CH 4 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 CH 4 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 frigida and Cleistogenes squarrosa (AC), and (4) Artemisia frigida , Cleistogenes squarrosa and concentrate supplementation (ACC). CH 4 production was significantly lower in July than in August (31.4 and 36.2 g per sheep‐unit per day, respectively). The daily average CH 4 production per unit of digestive dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) increased by 10.9, 11.2 and 42.1% for the AC diet compared with the LC diet, respectively. Although concentrate supplementation in both the AC and LC diets increased total CH 4 production per sheep per day, it improved sheep productivity and decreased CH 4 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 CH 4 emission from sheep was increased and concentrate supplementation increased diet use efficiency. Sheep‐grazing ecosystem seems to be a source of CH 4 when the stocking rate is over 0.5 sheep‐units ha −1 during the growing season in the Inner Mongolia steppe.