Study on evaluation of forage nutritions and nutritional carrying capacity in grassland of Kobresia tibetica grassland in Yushu Prefecture

In order to evaluate the carrying capacity of Kobresia tibetica grassland which was one of the main grassland types in Yushu Prefecture, three Datong yaks (five years old) were chosen to provide rumen solution, nutritional value of forage in K. tibetica grassland from Yushu prefecture belonged to Sanjiangyuan Region, and were evaluated in vitro with gas production method and conventional nutritional analysis method, and combined with forage yield, the carrying capacity of K. tibetica grassland was calculated. The results were as follows: 1) the yield of fresh forage, dry forage and edible forage of K. tibetica forageland were 1 272, 349.04, 341.29 g·m-2 respectively; 2) CP, EE, ADF, Ash, Ca, P were 10.16%, 2.26%, 34.07%, 4.76%, 0.31%, 0.11%, respectively; 3) the values of DOM, DE and ME were estimated according to the content of CP, EE and gas production of 120 h, which were 81.21%, 10.33 MJ·kg-1, 9.16 MJ·kg-1, respectively, and dry matter digestibility (DMD), ammonia nitrogen concentration(NH3-N), pH value were 62.67%, 7.72 mg·dL-1 and 6.65, respectively, and the curves of gas production rate showed the shape of single-peak (20―28 h); 4) the carrying capacity of production, ME and DCP for K. tibetica grassland in Yushu Tibetan Autonomous prefecture were 14.11(8.44 sheep units per hectare), 20.51(13.16 sheep units per hectare) and 22.02(12.26 sheep units per hectare) million sheep units approximately.