Electrical conductivity of milk in different milking phases and relationship with subclinical mastitis and mastitis pathogens of cows

Abstract

The aim of the study was to investigate the relationships between the electrical conductivity of milk in different milking phases with subclinical mastitis and productivity of cows. Three hundred fourteen Lithuanian Black and White cows in 2-4 lactation months were evaluated with Lactocorder®. We found on average 6.28 mS/cm and 7.17 mS/cm, for respectively electrical conductivity at highest milk flow (ELHMF) and electrical conductivity during the initial time (ELAP). The average was 6.66 mS/cm for the maximum electrical conductivity after reaching the highest milking speed (ELMAX) and 0.79 mS/cm for (beginning peak difference of the electrical conductivity (ELAD). The somatic cell count (r=0.196) and milk yield (r=-0.222) showed the strongest unfavorable correlation (P<0.01) with ELHMF. Higher ELHMF was related to a greater frequency of mastitis. Pathogens of intramammary gland were found by 39 % of cows in group of ELHMF<6 mS/cm and 52% - in group of ELHMF≥6 mS/cm (P=0.002). The milk from cows infected subclinically with Staphylococcus aureus had 0.55 - 0.68 mS/cm higher ELHMF, than with subclinically Streptococcus agalactiae, Streptococcus uberis, Streptococcus dysgalaetia (P<0.001).