Pilot study

Impact of using a culture-guided selective dry cow therapy program targeting quarter-level treatment on udder health and antibiotic use

Abstract

The study objective was to evaluate the effects of applying a culture-guided, quarter-level selective dry cow therapy (SDCT) program on udder health and antibiotic usage as compared to blanket dry cow therapy (BDCT). Two days prior to dry-off (DO), 56 cows were randomly assigned to a BDCT or SDCT group and aseptic quarter milk samples were collected for laboratory culture. For cows in the SDCT group, milk from each quarter was also cultured using a rapid culture system, with results recorded as bacterial "growth" or "no growth". On the day of DO, cows in the BDCT group were infused with an antibiotic and an internal teat sealant in all 4 quarters. For cows assigned to the SDCT group, quarters with bacterial growth were infused with an antibiotic plus internal teat sealant, while quarters with no growth were infused with internal teat sealant only. Quarter milk samples were collected days 1 through 7 after calving for laboratory culture, and clinical mastitis events were recorded between DO and 30 days-in-milk. Logistic regression was used to evaluate the effect of treatment on measures of udder health after calving. Results showed no effect of treatment on quarter level risk for presence of infection after calving ( 42.1 % vs 39.6%), cures (82.3% vs 88.0%), or new infection ( 41.5% vs 40.2%) for the SDCT and BDCT group, respectively. Antibiotic use was reduced by 48% in the SDCT group. Results of this pilot study suggest that a culture-guided quarter-level SDCT program can achieve equal udder health compared to BDCT, while significantly reducing antibiotic use at DO.