Electrical conductivity of milk as a phenotypic and genetic indicator of bovine mastitis: A review

This review presents the scientific background of the relationship between electrical conductivity (EC) of milk and bovine mastitis, and the possibility of using EC as an indicator trait in a breeding program is discussed. Electrical conductivity of milk was introduced as an indicator of mastitis several decades ago. Until now EC has solely been used for detection of bovine mastitis on the phenotypic level. However, EC may be used as an indicator of mastitis in a breeding program where selection against mastitis is included. Somatic cell score (SCS) has been widely considered to be the most useful indirect measure of mastitis. However, using SCS for genetic evaluation has some disadvantages such as low recording frequency. Most automatic milking systems are equipped with sensors for measuring EC, and EC can be easily recorded at every milking. Heritability estimates of EC are found to be moderate, ranging from 0.12 to 0.36, depending on the trait definition and the model used. Genetic correlations between EC and mastitis have been estimated to be in the range from 0.65 to 0.8, hence, obtaining genetic response for mastitis should be possible by using information of EC in genetic evaluation. However, collecting and implementing EC information in a breeding program may be a challenge.