engleski

Evaluation of the Zagreb mastitis test as a screening method to detect subclinical mastitis in dairy cattle

Mastitis is the most prevelant production disease in dairy herds world-wide and is responsible for serious economic losses due to decreasing milk production and lower quality of milk. Therefore, screening of subclinical mastitis under field conditions is of great importance in dairy farming. The aim of present study was to estimate prevalence of bacterial mastitis in dairy cattle in the northern part of Croatia as well as to evaluate Zagreb mastitis test as a screening test for diagnosis of subclinical mastitis in dairy cattle. In the period 2005-2008, 1549 quarter milk samples from 389 Simmental dairy cows were subjected to Zagreb mastitis test (ZMT) and bacteriological examination and In 760 (49.06%) quarter milk samples microorganisms were found. The most isolated microorganisms St. aureus, Streptococcus D, and P. aeruginosa were found in 388 (51.05%), 84 (11.05%), 62 (8.16%) positive quarter samples, respectively. Using a cut-off of ZMT by scores at ≥1 as positive, 63.20% (CI 95% 60.80-65.60%) quarter samples were estimated as being positive for subclinical mastitis. This cut- off had quite high sensitivity (96.84%, CI 95% 95.60-98.06%) and predictive negative value (95.79%, CI 95% 94.14-97.44%), however specificity (69.20%, CI 95% 65.98-72-42%) and predictive positive value (75.17%, CI 95% 72.47-77.86%) were low. Using a ZMT cut-off of ≥2 as positive, 48.16% of quarters were positive. Sensitivity (82.76%, CI 95% 80.08-85.45%) and specificity (85.17%, CI 95% 82.69-87.65%) as well as predicative values were similar. Likelihood ratio by cut-off of ≥1 and cut-off of ≥2 was 3.14 and 5.58, respectively.

evaluation; Zagreb mastitis test; screening method; subclinical mastitis; dairy cattle

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