EFFECTS OF PARITY, SEASON AND ANTIBIOTIC-THERAPY ON PREVALENCE OF MASTITIS PATHOGENS IN MAMMARY SECRETION OF DAIRY-COWS

The prevalence of mastitis pathogens in cow milk samples of a herd (34 - 44 cows) was highest at the beginning of experiment (in March), when 25 cows (58.1 %) were infected in 25.4 % of quarters. S. agalactiae was isolated from milk samples of 13 cows (27 quarters). By use of adequate treatment of clinical mastitis cases during lactation and dry cow therapy (from September), the number of infected cows decreased mainly due to the decrease of S. agalactiae infections to 12 animals during one year. In spite of the fact that prevalence of infections in the herd decreased, somatic cell count (SCC) in bulk tank sample and the frequency of clinical mastitis seasonaly increased in summer due to increase of incidence of coliform bacteria infections. Coagulase-negative staphylococci were often isolated from mammary secretion of pregnant heifers (87.4 %) of all pathogens), less from colostrum and milk of first-calf heifers (48.8%) and milk of older cows (13.6 %). On the other hand prevalence of streptococci was highest in secretion of older cows (72.4 %), less in first-calf heifers (45.1 %) and pregnant heifers (12 %).