Estimation of diet composition and herbage intake of grazing sheep at different stocking rates in Inner Mongolia typical steppe by using n-alkanes technique Studies on Productivities for Dairy Cows under Different Grazing System and Grazing Intensity──1. Effect of Grazing on Herbage Intake and Nutrients Ingestion Estimation of Diet Composition and Herbage Intake of Grazing Cows using n-Alkane Technique in Inner Mongolia Typical Steppes