The aim of this study is to determine the risk factors for subclinical mastitis, and the effect of the breed, number and stage of lactation of cows on their frequency in dairy cattle farms in the Constantine region. The study involved 20 small and medium herds of dairy cattle from the Constantine region in eastern Algeria. A survey was conducted for the collection of data concerning: the number of cows, the exploited breeds end the type of breeding. The California Mastitis Test (CMT) was carried out for the detection of subclinical mastitis. The results of the survey show that Prim'Holstein is the most exploited breed by dairy farmers. The number of dairy cows exploited ranges from 3 to 80 cows. Animal housing consists of concrete floor in 95% of farms. The results of CMT show that the race most affected by subclinical mastitis is Montbeliarde, thus, the incidence of mastitis is higher in the first and third thirds of lactation, however, the incidence of mastitis has been little modified by the lactation number of the cows.

Key words: Dairy cows, Subclinical mstitis, Survey, CMT, Constantine