SUBCLINICAL MASTITIS IN LACTATING COWS: COMPARISON OF FOUR SCREENING TESTS AND EFFECT OF ANIMAL FACTORS ON ITS OCCURRENCE
Keywords:Sub clinical mastitis, risk factors, bacteriological culture, California mastitis test, somatic cell count
A total of 444 quarter milk samples from 111 crossbred dairy cows were subjected to California mastitis test (CMT), somatic cell count (SCC) test, white side test (WST) and surf field mastitis (SFMT) test to quantify their efficacy in detecting sub clinical mastitis in dairy cows of Bangladesh during the period from 2010 to 2011.Milk samples positive by CMT, SCC, WST and SFMT were 265,230, 225 and 222 respectively. All samples were subjected to cultural isolation (gold standard test for comparison of indirect mastitis tests). Of these, 261 samples were positive by cultural isolation. The sensitivity of the CMT, SCC, WST and SFMT were 80.08%, 86.60%, 60.54% and 57.47%; specificity 69.40%, 97.81%, 63.38% and 60.66%; percentage accuracy 75.68%,91.22%, 61.71% and 58.78%; positive predictive value 78.87%, 98.26%, 70.22% and 67.57%; and negative predictive value 70.95%, 83.64%, 52.97% and 50%respectively. Quarter-wise sub clinical mastitis (SCM) was detected in 59.68%, 51.80%, 50.68% and 50% samples by CMT, SCC, WST and SFMT, respectively, while animal-wise SCM was recorded in 72.07%, 66.67%, 64.86% and 61.26% samples by CMT, SCC, WST and SFMT, respectively. The right hind quarters were most significantly (p<0.001) susceptible to SCM than other quarters. Cows with 3rd and 4th parity and at their early lactation stage had significantly higher (p<0.001) SCM than others. Kappa value of SCC was higher than that of CMT. CMT was concluded to be the most accurate test after cultural isolation and SCC. Unlike laboratory tests as cultural isolation and SCC that require adequate laboratory facilities and skilled personnel, CMT is a reliable diagnostic method in field conditions.