Comparison of cow-side diagnostic tests for subclinical mastitis of dairy cows in Musanze district, Rwanda

Abstract

Four subclinical mastitis diagnostic tests (the UdderCheck^® test [a lactate dehydrogenasebased test], the California Mastitis Test [CMT], the Draminski^® test [a conductivity-based test] and the PortaSCC^® test [a portable somatic cell count-based test]) were compared in a study comprising crossbreed dairy cows (n = 30) during September and October 2015. Sensitivity and specificity of the CMT, Draminski^® and UdderCheck^® tests were compared with the PortaSCC^® as reference. The CMT, Draminski^® and UdderCheck^® test results were compared with the results of the PortaSCC^® test using kappa statistics. Duplicate quarter milk samples (n = 120) were concurrently subjected to the four tests. Sensitivity and specificity were 88.46% and 86.17% (CMT), 78.5% and 81.4% (Draminski^®) and 64.00% and 78.95% (UdderCheck^®). The CMT showed substantial agreement (k = 0.66), the Draminski^® test showed moderate agreement (k = 0.48) and the UdderCheck^® test showed fair agreement (k = 0.37) with the PortaSCC^® test and positive likelihood ratios were 6.40, 4.15 and 3.04, respectively. The cow-level subclinical mastitis prevalence was 70%, 60%, 60% and 56.7% for PortaSCC^®, CMT, Draminski^® and UdderCheck^® tests, respectively. At udder quarter level, subclinical mastitis prevalence was 20%, 21.67% and 20.83% for PortaSCC^®, CMT and UdderCheck^®, respectively. A correlation (P < 0.05) and moderate strength of association were found between the four tests used. The study showed that compared to the PortaSCC^® test, the CMT was the most preferable option, followed by the Draminski^® test, while the UdderCheck^® test was the least preferable option for subclinical mastitis screening.