بررسی تغییرات فصلی بار میکروبی و سلول های سوماتیک شیر در گاوداری های استان همدان

Background: microbial contamination and somatic cells are account as two important factors in reducing the shelf life and entire quality of raw and pasteurized milk. objectives:this study was carried out on the seasonal variation of milk microbial and somatic cell counts. methods:six industrial and traditional dairy farms from hamedan province were sampled monthly for a period of one year. records of somatic cell and bacterialcount of samples were analyzed by using different statistical methods in sas software. results:least square mean (±se) somatic cell count (cells per ml×1000) and total microbial was 325.10(± 13.20) and 5287.03(± 261.23), respectively. differences in microbial count in industrial and traditional farms was significant (p < 0.0001). seasonal changes in total count was significant (p < 0.0002) and the effect herd nested in farming system was significant (p < 0.0001) as well. also there were significant difference in farming system and herd on somatic cell counts (p < 0.0001).conclusions:although industrial dairy farms had lower total count than traditional dairy farms,the somatic cell counts were higherand need to be more investigated on annually herd combination, dry-off time and cutting strategy of low producing and infertile dairy cows.