Acute phase protein as biomarker for diagnosis of sub-clinical mastitis in cross-bred cows

The present study was carried out to investigate the role of acute phase proteins [Serum amyloid A (SAA) and milk amyloid A (MAA)] for diagnosis of sub-clinical mastitis in cross-bred cows. The study was conducted on 40 apparently healthy cross-bred cows, in the mid-lactation period and were equally divided into four groups [Group-I (Bacteriologically negative milk samples, California mastitis test (CMT) negative), Group-II (Bacteriologically negative with SCC ≤200,000 cells/ml milk, CMT positive), Group-III (Bacteriologically negative with SCC ≥200,000 ≤500,000 cells/ml milk, CMT positive) and Group-IV (Bacteriologically positive with SCC ≥200,000 ≤500,000 cells/ml milk, CMT positive)]. On bacteriological examination of 57 milk samples, 27(47.36%) were found positive and 30 (52.63%) were found negative. A highly significant (P<0.01) differences in the mean values of SCC were observed between groups except group I and II and group III and IV. Highly significant (P<0.01) differences in mean values of SAA were reported between all groups except group I and II. Highly significant (P<0.01) differences in mean values of MAA were observed between all groups except group III and IV. Results of the correlation matrix revealed strong positive correlations (P<0.01) of SCC with SAA and MAA; and between SAA and MAA. The proposed cutoff points for SCC, SAA and MAA were >200,000 cells/ml, 74 μg/ml and 10 μg/ml, respectively for the diagnosis of sub-clinical mastitis with high sensitivity (90% to 100%). The area under curve of the SAA was larger than those of SCC and MAA, which suggests that the SAA test was more accurate than SCC and MAA for the diagnosis of sub-clinical mastitis.