Lactate dehydrogenase: Detecting high bacterial and somatic cells counts in goats from whole milk samples

Abstract

The efficacy of using only somatic cell count (SCC) in goats to study the milk quality as a single test has been widely questioned, with total bacterial count being considered as ancillary test in several studies. Therefore, the main objective of this study was to identify new biomarkers of interest that correlate with high SCC and TBC values in milk samples. The concentration of five selected proteins according to their association with infected and injured udders (milk amyloid A, lactoferrin, pentraxin 3, N-acetyl-beta-d-glucosaminidase and lactate dehydrogenase) were determined in bulk raw milk together with SCC and TBC values. Only LDH showed a significant positive correlation with respect to SCC or TBC, no correlation between the other proteins with respect to both parameters were detected. Following, LDH activity and SCC and TBC values were analyzed in a wide diversity of goat milk samples performing a receiver operating characteristic (ROC) curve analysis. LDH showed a significant positive correlation with both SCC and TBC values. LDH activity differed significantly between milk samples with a high and/or low SCC and TBC with a sensitivity that can reach values of 91.3 % and a specificity of 83.2 %. Our results, highlight LDH activity measurement as a biomarker of interest in raw milk for the detection of low-quality milk samples which could potentially be used for the diagnosis of subclinical mastitis in goats.