The use of Na+ and K+ ion concentrations as potential diagnostic indicators of subclinical mastitis in dairy cows

Aim: This study was conducted to evaluate the concentrations of sodium (Na+) and potassium (K+) ions in milk of lactating dairy cows with and without subclinical mastitis as putative indicators for detecting subclinical mastitis in dairy cows. Materials and Methods: Thirty seven lactating dairy cows were screened for the evidence of subclinical mastitis using California mastitis test (CMT). The lactating dairy cows were categorized as CMT-Positive (CMT-P; n=20) and CMT-Negative (CMT-N; n=17) based on whether they were positive or negative for CMT using a standard kit. The CMT-P lactating dairy cows were further sub divided into subclinical 1+ (S1+; n=6), subclinical 2+ (S2+; n=9), and subclinical 3+(S3+; n=5). Direct microscopy somatic cell count (SCC) was used to determine the SCC using Wright's stain. The samples were filtered and diluted at 1: 100 dilutions before being measured for the concentrations of Na+ and K+ using atomic absorption spectrophotometer. Results: There was a significant increase (p<0.05) in SCCs and Na+ concentration in the milk of CMT-P dairy cows, with a mean Log 10 SCC score of 5.35 +/- 0.06 cells/ml and mean Na+ concentration of 232 +/- 19.1 mg/dL. However, there was a significant reduction (p<0.05) in the concentration of K+ (123 +/- 7.6 mg/dL) in the milk samples of the CMT-P cows. There were significant differences (p<0.05) in SCC, Na+ and K+ concentrations between milk samples from the CMT-N dairy cows and CMT-P subgroups; S1+, S2+, and S3+ respectively. Potassium (K+) concentration had a significant strong negative correlation with sodium (Na+) concentration (r=-0.688; p<0.01) and weak positive correlation with SCC (r=-0.436; p<0.01). The sensitivity of using Na+ and K+ concentrations as detection indices for sub-clinical mastitis is 40% and 90%, respectively, while the specificity of each was 100%. Conclusion: This study thus shows that evaluation of Na+ and K+ concentrations from milk samples of dairy cows with sub clinical mastitis can be of immense diagnostic benefit and will compliments detection using CMT alone.