Investigation the preference value of the some speciesIn Sahand rangelands of East Azarbaijan province

In this research, the preference value of rangeland species in Sahand rangelands of East Azarbayjan province was studied for four years (2007-2010). The preference index method was used for this purpose. After determining the amount of production and consumption of each species selected in the grazing season (June, July, August, and September) and calculating the share of each species in the forage production of the region and livestock feed, and calculating the preference index, the data analyzed in split-plot design based on the completely randomized design in SAS software. The results showed that the effect of the year in three species, the effect of the month in four species, and the interaction of year and four species at (p≤0.01) were significant on the preference index. The preference index is a very important factor in determining the preference value of plant species for livestock. The species of Festuca rubra, Tanacetum chiliophyllum, with an average preference index of 1.4 to 1.6 during four-year, has a relative preference and is a relatively benign species and was placed in the palatable class I. Tanacetum chiliophyllum, with the highest average preference index, was ranked first among all herbaceous species. The species of Bromus tomentellus, Festuca ovina, Alopecorus textilis with an average preference index of 0.7 to 1.2 were of moderate preference and were classified as moderate in palatability and classified in the palatability class II.  Astragalus aureus, with an average preference index of about 0.3, had a relative preference, and this species was almost non-chewed and ranked in the palatable class III. Overall, the results of this study showed that the preference value of Festuca rubra and Tanacetum chiliophyllum was more than the other species, and the sheep preferred the forbs, followed by grasses and shrubs for sheep grazing.