Proportion of oat grass and natural herbage in summer on the digestive metabolism of Tibetan sheep

In this study, four mixed diets with different proportions of oat grass and alpine meadow natural herbage were used to carry out a simulated grazing experiment. The effects of summer cultivated different proportions of oat grass were mixed with natural herbage feeding on the digestion and metabolism of grazing Tibetan sheep were subsequently studied. Our results showed that the intake and digestibility of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and acid detergent fiber (ADF) decreased with increasing oat grass proportions. A greater than 50% of oat grass significantly reduced the DM and OM intake and digestibility in Tibetan sheep (P < 0.01). The fecal nitrogen content presented a concave parabola change with increasing nitrogen intake. When the daily nitrogen intake was 4.65 g, the daily fecal nitrogen content was the lowest, at 1.13 g. As nitrogen intake increased, the digestibility of nitrogen presented a convex parabola. The digestibility of nitrogen was the highest, at 76.53%, when the daily nitrogen intake was 5.60 g. Total energy intake decreased with the increase of oat grass ratio. In conclusion, in summer, all natural herbage can meet the growth and metabolism of Tibetan sheep, and it is not suitable to feed additional oat grass.