Screening ofbulk tank milk in fifty seven dairy herds in Tehran suburb

Subclinical mastitis is a serious dairy herd problem. many infected cows contrib ute to the low prod uction and high somatic cell count (scc), which reduce milk quality premiums. bulk-tank milk analysis is a useful tool for improving milk quality in a dairy operation. a crosssectional survey of 57 dairy farms in the suburb of tehran was carried out with sampling in 3 consecutive intervals. milk samples were cultured and divided in four groups based on total bacterial count (tbc) and scc. twenty six samples had tbc<50000 and scc>25 0000 (group 1), 18 samples had tbc >= 50000 and scc>250000 (group 2), 7 samples had tbc<50000 and scc =< 250000 (group 3) and 6 samples had tbc>=50000 and scc =< 250000 (group 4) .the microorganisms isolated from the 4 groups in order 14 were: streptococcus aga lactiae (4, 0, 0 and 2), staphy lococcu s aureus (7,6,3 and 1 in 4), high level ofstreptococcus uberis (4, 2, 3 and 3 in 4), stre ptococcus dysgalactiae (3, 5,4 and 1) , high level escheric hia coli (23, 16, 5 and 4), high level klebsiella speci es (2, 1, 0 and 0), high level enterobacter (3, 2, 4 and 0), high level citro bacter (10 , 13, 5 and 2), high level coagulasenegativestaphylococc us (21, 12, 5 and 6), pseudo monas aeroge nese (13, 10, 2 and 5), proteus (6, 1 , 2 and 0), serratia marcescens (2, 2, 0 and 2), nocardia astroides (3, 0, 1 and 1 ), listeria monocytogenes (2, 1 , 1 and 0) and edwardsiella tarda (0, 1, 1 and 0). in thi s study except prototheca and bacillus, other above mentioned pathogens were isolated in the culture, presence of most these pathogens in btm indicate that there are problems in our mastitis control programs in our dairy farms.the presentscreening study may help to design mastitis prevention protocols in the future .