Effects of Herbages and Diet Composition on Rumen Fermentation,Nutritional Degradability and Methane Emission of Sheep in the Inner Mongolia Steppe

The effective utilization of forage and control of methane emission from grazing sheep could be influenced by the changes of grassland community structure and nutrient composition of forages.The aims of this experiment,conducted in the Xilingol grassland,were to study the effect of ingredient and quality of forages on rumen fermentation,nutritional degradability and CH_4 emission.The results indicate that forages of different growing seasons affected their palatability,the sheep's feed intake and digestibility.Leymus chinensis is nutritious and digestible forage.Supplement concentrate in the diets increased the feed intake,digestibility of main nutrient and daily gain weight of sheep.Different supplements of diet significantly affected the ruminal juice,as high crude protein content in the diet increased the concentration of NH_3-N in the rumen.Forages of different growing seasons and types affect significantly the concentration of total VFA,though not on the proportions of individual VFA.The positive nitrogen balance in the four diets and the higher nitrogen retention and availability in the group of supplement concentrate were observed.There was a significant positive correlation among the amount,the intake,the digestion and retention of nitrogen.The degradability of OM,CP and NDF could be estimated using the regression equation of dependent DM.There were interactions among the effective degradability of DM,OM and NDF.The effective degradability of DM and DNF decreased with the increase of their content in forages.No significant correlation existed between the effective degradability of CP and DM,OM and NDF content in forages.The CP content in forage did not affect its effective degradability.CH_4 production was notably 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 DM,OM and NDF increased 10.9%,11.2%,and 42.1 %,respectively,for AC diet,compared with LC diet.Although supplemented concentrate in both diets increased the total CH_4 production per sheep per day,it improved sheep productivity and decreased CH_4 production 14.8%,12.5% and 14.8% per unit of DM,OM and NDF digested by sheep,respectively.The results suggest that degraded grassland increased CH_4 emission from sheep and supplemented concentrate enforced the diet efficiency.Sheep grazing ecosystem seems to be a source of CH_4 when the stocking rate is over 0.5 sheep-unit ha~(-1) during the growing season in the Inner Mongolia steppe.Saponin and ropadiar additive can be used to mitigate the methane production from sheep and yields long-term environmental benefits.