Detection of Clinical Mastitis by Changes in Electrical Conductivity of Foremilk Before Visible Changes in Milk

¹ Institute for Animal Health, Compton, Newbury, Berkshire, United Kingdom RG20 7NN

Mastitis was induced by the direct infusion of Staphylococcus aureus or Streptococcus uberis into the mammary gland of lactating cows. Changes in electrical conductivity of foremilk indicated the establishment of bacteria, increased SCC, increased clotting of milk, and, hence, disease in advance of visible changes in the milk that could be diagnosed by a herdsperson. Clinical mastitis was detectable by changes in electrical conductivity of foremilk, 90% of cases were detectable when clots first appeared in foremilk, and 55% of cases were detectable up to 2 milkings prior to the appearance of clots. All subclinical infections from Staph. aureus were detected, but subclinical infections from Strep. uberis were not detected. The result suggested that clinical mastitis caused by these two major pathogens could e detected earlier by measuring changes in electrical conductivity of milk than by waiting for a herdsperson to detect visible changes in milk. Earlier detection would permit earlier treatment. However, the hand-held sensor used in this experiment is impractical for commercial application, and reliable automated sensors and decision-making algorithms are required.

Key Words: electrical conductivity • Staphylococcus aureus • Streptococcus uberis • mastitis

Submitted on May 5, 1995
Accepted on September 18, 1995

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