The Effects of Early Antibiotic Treatment Following Diagnosis of Mastitis Detected by a Change in the Electrical Conductivity of Milk

Mastitis was induced experimentally by infusion of Streptococcus uberis or Staphylococcus aureus into the mammary glands of lactating dairy cows. Clinical mastitis was identified when clots appeared in foremilk (conventional diagnosis) or was predicted by changes in the electrical conductivity of foremilk (early diagnosis). The responses to intramammary antibiotic treatment that was initiated after early diagnosis of mastitis and after conventional diagnosis were compared. Early treatment significantly limited the severity of the disease and, in many cases, prevented the appearance of any visible signs of infection. Milk yield was less depressed, and the somatic cell count (SCC) was lower, when treatment was initiated earlier. The SCC of the quarter at the time mastitis was predicted was approximately 2 × 10⁶ cells/ml for both pathogens, which was significantly less than when clots appeared at conventional diagnosis, approximately 4 × 10⁶ and 12 × 10⁶ cells/ml for Staph. aureus and Strep. uberis, respectively. The time required for SCC to recover to <4 × 10⁵ cells/ml was significantly less, approximately half, for both pathogens following early detection and early initiation of treatment. When treatment was administered in response to early detection, the bacteriological and clinical cure was almost complete, and the amount of antibiotic used was ≤50% less. Obvious benefits for milk yield and quality and the health of the cow would result when changes in the electrical conductivity of milk are used to predict clinical mastitis and when treatment is initiated early.