Intramammary infection at calving following Petrifilm-based selective dry cow therapy

Abstract

For producers motivated to reduce the use of antimicrobials on their farms, teat sealant-based selective dry-cow therapy (SDCT) offers an alternative to blanket dry-cow therapy (BDCT). Under a SDCT program, antimicrobial dry-cow preparations (DCT) are reserved for cows that are suspected, or known, to have an intramammary infection (IMI) at dry-off. Internal teat sealants (ITS) are a non-antimicrobial treatment that have been shown to be protective against new IMI during the entire dry period. Internal teat sealants are recommended for all cows as they enter the dry period, but their role is particularly important for cows not selected to receive DCT in a SDCT program. Determination of a cow's IMI status at dry-off is essential to the success of any SDCT program. Petrifilms are culture media plates that allow producers to culture milk on-farm, with results available in 24 hours. Petrifilms had a sensitivity of 85.2% and a specificity of 73.2% when used to diagnose IMIs in low somatic cell count (SCC; < 200,000 cells/mL) cows at dry-off. The objective of this study was to compare IMI at calving between cows that received BDCT and cows selectively treated on the basis of Petrifilm culture results.