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

Aim: This study was conducted to evaluate the concentrations of sodium ([Na.sup.+]) and potassium ([K.sup.+]) 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.sup.+] and [K.sup.+] using atomic absorption spectrophotometer. Results: There was a significant increase (p < 0.05) in SCCs and [Na.sup.+] concentration in the milk of CMT-P dairy cows, with a mean Log10 SCC score of 5.35 ± 0.06 cells/ml and mean [Na.sup.+] concentration of 232 ± 19.1 mg/dL. However, there was a significant reduction (p < 0.05) in the concentration of [K.sup.+] (123 ± 7.6 mg/dL) in the milk samples of the CMT-P cows. There were significant differences (p < 0.05) in SCC, [Na.sup.+] and [K.sup.+] concentrations between milk samples from the CMT-N dairy cows and CMT-P subgroups; S1+, S2+, and S3+ respectively. Potassium ([K.sup.+]) concentration had a significant strong negative correlation with sodium ([Na.sup.+]) concentration (r = -0.688; p < 0.01) and weak positive correlation with SCC (r = - 0.436; p < 0.01). The sensitivity of using [Na.sup.+] and [K.sup.+] 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.sup.+] and [K.sup.+] concentrations from milk samples of dairy cows with sub clinical mastitis can be of immense diagnostic benefit and will compliments detection using CMT alone. Keywords: potassium ion, sodium ion, somatic cell count, subclinical mastitis.