The Indicators of Clinical and Subclinical Mastitis in Equine Milk

SIMPLE SUMMARY: Mastitis, the inflammation of the mammary gland, is a major problem in a mare’s perinatal period, negatively affecting both the health of the mare and newborn foal and the quality of milk produced on dairy equine farms. The detection of mastitis is therefore one of the important goals in the equine breeding and dairy industry. This study aimed to determine the somatic cell count (SCC), the percentage of the immune cells, the electrical conductivity (ECM), and bacteriological index (BII) in milk collected from mares with (CM) and without (NCM) clinical symptoms of mastitis. The increase in examined indicators is suspected to be a subclinical mastitis indicator, therefore the study aimed to separate two subgroups, mares with (SM) and without (NSM) subclinical symptoms of mastitis. In milk from NCM mares the values of SCC, immune cells, and ECM increased immediately after birth and weaning, whereas during the rest of the lactation period their values were at a low level. Similarly, in milk from CM mares, the values of examined indicators were high and comparable to the weaning time. An increase in the level of examined indicators may become an early indication of subclinical mastitis. ABSTRACT: The somatic cell count in milk (SCC) and electrical conductivity of milk (ECM) are indicators of the health status of the mammary gland. Among somatic cells, mainly polymorphonuclear neutrophils (PMN), macrophages (MAC), and lymphocytes (LYM) are rated. This study aimed to determine the SCC, PMN, MAC, LYM, ECM, and bacteriological index (BII) in milk collected from mares with (CM) and without (NCM) clinical symptoms of mastitis concerning mares with (SM) and without (NSM) subclinical mastitis. Milk samples were collected from 27 mares divided into NCM (n = 12) and CM (n = 15) groups. In samples, SCC quantification, cytological examinations, ECM measurement, and bacteriological examination were performed. In NCM mares, the values of SCC, PMN, MAC, LYM, and ECM were higher in initial than in consecutive examined days after birth until weaning. After weaning the proportion of SCC, PMN, MAC, LYM, ECM, and BII increased and did not differ with the average values in CM mares. These equine milk indicators may reflect an early symptom of subclinical mastitis and in the future may be used in the early detection of mastitis or as a tool of assessment of the health status of the mammary gland in the dairy equine farm.