Abstract: 3 yaks,4 years old, with permanent rumen fistula, which had 1/2 wild blood, were chosen to assess nutritional value of Qinghai local oat hay with in vitro gas production method and nylon bags method. The result showed that in oat hay,the content of CP was 7.17%,EE was 2.23%,NDF was 54.86%,ADF was 29.15%;dry matter digestibility of oat hay in 72 h which was measured by in vitro gas production method is 87%,by nylon bags method was 80.56%. We estimated that the digestibility of ODM was 89.30%,ME was 13.99 MJ/kg DM.The dry matter digestibility of oat hay in 4,6,8 h were a little higher than the rate which was measured by in vitro gas production method;dry matter digestibility which were measured in period of 12,24,36,48,72 h were a little lower than the rate which were measured by in vitro gas production method, but there was no significantly different (P>0.05).We analyzed the relationship of the two methods, then we got r=0.98,it showed that the relationship of this two methods was positive.

Key words: in vitro gas production method; nylon bags method; digestibility; oat hay; yak