From 88 primiparous cows, belonging to four dairy herds, during 120 days after parturition, one thousand and eighty five milk samples collected, showed 457 (23.02%) positive microbiological results. Coagulase negative staphylococci (CNS) were isolated in 316 (69.14%) samples, Corynebacterium bovis in 56 (12.25%), streptococci in 41 (8.97%) and coagulase positive staphylococci (CPS) in 38 (8.31%). Clinical mastitis was detected in 9 (10.23%) cows. In the first day after parturition, 57 (64.77%) animals and 114 (32.66%) quarters were bacteriologically positive. Until the 14th day there was a remarkable decrease in the number of infections in cows and in quarters, numbers which tended to stabilize later. CNS were isolated through all the experiment while the streptococci tended to disappear in the first few weeks. The infections by C. bovis steadily increased after parturition. Of CNS, S. hyicus and S. intermedius were predominant, and in the streptococci the C and D groups. The average somatic cell count (SCC) was 508.914/m<img src="http:/img/fbpe/cr/v31n6/a18img01.gif"> in the infected ones and in the negative quarters It was 73.942/m<img src="http:/img/fbpe/cr/v31n6/a18img01.gif">.
mastitis; aetiology; primiparous cows
