Etiology of mastitis in ewes and possible genetic and epigenetic factors involved

Abstract

The paper reviews the knowledge related to the possible relationship of somatic cell counts to udder health and milk yield in dairy ewes. It attempts to point out the epigenetic and genetic aspects of udder health, methods for diagnostic of mastitis and pathogens involved. The possible physiological level of somatic cell counts (SCC) to establish the limits for ewe’s milk are discussed. Data from the worldwide research are compared with limited results obtained in Slovakian dairy practice. Globally, applied research has focused on understanding of the relationship between SCC and mammary gland health through the presence of microorganisms. Many milk samples with high SCC are microbiologically negative, underlining the importance of research at the molecular level. Limits for SCC indicating health problems of ewe’s udder are not yet established but during the last decades the proposal for limits decreased with time. Most paper considered 0.5 × 106 cells.mL-1 or below for healthy udders. Data obtained from bulk milk showed that only 7.3 % of the samples were in the category below 0.5 × 106 cells.mL-1 under Slovakian conditions. Possible genetic and epigenetic factors are discussed in this paper in relation to SCC. The identification of a genetic marker(s) that allows the inclusion of mastitis resistance in selection programmes would help to reduce the economic impact due to this disease. Subclinical mastitis is considered as a limiting factor for milk production. Several works have been published which presented a negative correlation between SCC and milk production.