CLINICAL MASTITIS IN MACEDONIAN DAIRY HERDS

The purpose of this study is the determination of the occurrence and prevalence of clinical mastitis and lactation incidence risk on three dairy farms. A one year study on a total of 1031 black-white breed cows with a total of 1267 lactations was performed. Each daily farm implemented a different technology of rearing and was of different herd size (farm A - tie-stalls, 162 cows; farm B - loose-housing system with open shed and deep bedding, 357 daily cows; and farm C - loose-housing system with enclosed shed, 512 cows). Clinical mastitis in cows was detected by clinical examination of the udder and determination of abnormalities in the milk. To distinguish two consecutive cases of clinical mastitis within the same lactation a time period of nine days was used. Annual prevalence rate of clinical mastitis for the entire population of cows was 34.13% on cow level, and 30.07% on lactation level. There was a high prevalence rate of clinical mastitis in primiparous cows, 21.43%, 40.77% and 12.55%, on farms A, B and C, respectively. Lactation incident risk for cows on farm A was 25.00%, farm B 95.58% and farm C 21.49%. The prevalence of clinical mastitis and lactation incidence risk tended to increase with increasing parity. The annual lactation risk for the entire population of cows was 45.86%. All indicators for the determination of the occurrence of clinical mastitis in daily farms, which were observed during the research, showed the greatest values on farm B. Most of the cows manifested one (68.24%) or two (18.63%) cases of clinical mastitis during lactation. There was a long period in lactation until the appearance of the first case of clinical mastitis (112.21 +/- 92.04 days). Generally, clinical mastitis was registered during the whole period of the survey, with some fluctuations between different seasons. The method of GLM (General Linear Model), univariate procedure, was used to analyze associations between the incidence of clinical mastitis and farm management, parity of cows and season of the year. Pearson's coefficient of correlation was performed for analysis of interdependence on variables in the model. There was statistical significance (p < 0,001) between the season and incidence of clinical mastitis.