Evaluation of a Petrifilm-based on-farm culture system for the detection of intramammary infections in cows with low somatic cell counts at dryoff

Abstract

As an alternative to blanket dry-cow therapy, teat sealant-based selective dry cow therapy (SDCT) has the potential to greatly reduce the amount of antimicrobials used in dairy production. The main obstacle to SDCT is the necessity for a rapid and cost-effective method of identifying which cows have an infection at dry-off and would benefit from dry-cow antimicrobial therapy (DCT). Ideally, this method of diagnosis would be applicable to on-farm use and be simple to interpret. Because failing to treat an infected quarter at the end of lactation can have detrimental effects on the subsequent lactation, the diagnostic test should also have high sensitivity. Petrifilms are a ready-made culture media that provide results within 24 hours and are suitable for on-farm use. The presence of an indicator dye in the Petrifilm medium makes aerobic bacterial colonies appear as bright pink dots against a white background. Petrifilms have been validated as a diagnostic tool for the selective treatment of mastitis in lactating cows. The objective of this study was to determine the utility of a Petrifilm-based on-farm culture system for making treatment decisions for cows with low somatic cell counts (SCC) at dry-off.