Evaluation of the use of the California Mastitis Test, last test somatic cell count, or a computer automated algorithm for detecting intramammary infection at dry-off

Abstract

Selective dry cow therapy (SDCT), the identification and treatment of only cows or quarters that have or are at risk for an infection over the dry period, constitutes a prudent strategy when considering antibiotic use. Milk culture by a professional lab, which takes ≥ 1 day and may not be accessible to all dairies, is currently recognized as the gold standard for determining intramammary infections (IMI). Identification of cows or quarters for SDCT requires timely and cost-beneficial diagnostics with acceptable sensitivities (Se) and specificities (Sp) to decrease under, as well as overtreatment of animals at dry-off (DO). For this purpose, our objectives were to explore the test characteristics of the California Mastitis Test (CMT), use of the last-test DHIA somatic cell count (LTSCC), and use of an automated algorithm (ALG) based on sequential somatic cell count (SCC) and mastitis events to identify IMI in quarters and cows at DO using 2 categories of IMI (all or only major pathogens).