Abstract: Feed intake is an important factor affecting the production performance of grazing livestock and plays an important role in determining outcomes in grassland ecosystems. This research compared groups of 4 sheep of differing age and sex (lamb, 1-, 2-, 3-, and 4-year-old ewes, wethers and stud stock, of Oula, Ganjia and Qiaoke types of Tibetan sheep). For these 21 groups of sheep, the feces output and organic matter digestibility were measured using the TiO₂ inert marker method and fecal nitrogen index method respectively in order to calculate grazing intake. The correlations between the various feed nutritive value, intake and digestibility data were also evaluated. The results showed that the average grazing intake of Oula, Qiaoke and Ganjia Tibetan sheep was 1032, 835 and 956 g·d^-1, respectively. Although the grazing intake of Qiaoke Tibetan sheep was significantly lower than that of Oula and Ganjia types (P<0.05), there was no significant difference among the three Tibetan sheep types in grazing intake per kg metabolic body weight or in the ratio of dry matter intake to body weight (P>0.05). The average organic matter digestibility of the Xiahe pasture when consumed by Oula, Qiaoke and Ganjia types of Tibetan sheep was 51%, 47% and 56%, respectively, and their average feces output was 561, 484 and 467 g·d^-1, respectively, with the difference in excretion of Oula Tibetan sheep being significantly higher than the values for the other two types of Tibetan sheep. The defecation, organic matter digestibility and grazing intake of the different types of Tibetan sheep were studied while grazing natural pasture in an alpine region in order to provide a sound scientific basis for the husbandry and management of Tibetan sheep.

Key words: alpine meadow, Tibetan sheep, grazing feed intake, TiO₂ inert marker, feces excretion, organic matter digestibility