RESUMEN
To determine sublicnial and clinical mycoplasmal mastitis and their frequency in dairy cattle herds. Prospective study. One hundred Holstein dairy cattle. Affected cows with clinical [n=19] and subclinical mastitis [n=81] were determined by using routine clinical methods and California Mastitis Test [CMT]. Samples were collected in the sterile tube containing Ampicillin. They were inoculated into both PPLO broth and PPLO agar for 96 hours and one week at 37 [degree sign] C, respectively. Chi-square test. Mycoplasma was isolated from 13 cows. The frequency rate of clinical and subclinical mastitis were 15.38% and 84.61%, respectively. There were no significant correlation between infected quarter and herd population [P>0.05]. The mammary glands of dairy cattle herds in suburb of Mashhad-Iran were infected by Mycoplasma. It is necessary to be investigated more in the field of mycoplasmal mastitis in dairy cattle herds