Observational study on application of a selective dry-cow therapy protocol based on individual somatic cell count thresholds

Selective dry cow therapy (SDCT) is one measure suggested to reduce the use of antibiotics on dairy farms. This procedure may have a negative impact on dairy herds, affecting both milk yield and quality. The aim of this observational study was to evaluate the implementation of a SDCT protocol based on the treatment only of cows with SCC at last individual milk test before drying-off >100,000 cells/mL (primiparous cows) or >200,000 cells/mL (pluriparous cows) on udder infection status. We also assessed the association between cow and management factors with the likelihood of cure or of new IMI across the dry period. The study considered 516 dairy cows (2064 quarters), and only 53% of the cows were treated with antibiotics. Before drying-off, 999 quarters (49.1%) were bacteriological negative at two consecutive samples. After calving the negative quarters were 1004 (49.3%). The likelihood of a cure across the dry period was significantly associated with parity, drying-off length and teat sealant application, while the likelihood of new IMI across the dry period was associated to all the risk factors considered (parity, dry period length, teat sealant application, infections status at drying-off and type of long-acting antibiotic applied). The application under field conditions of the proposed SDCT protocol showed to feasible, and to largely reduce the use of antimicrobials at drying-off, with a relatively small impact on cow health.