Differences in lactational performance associated with antimicrobial treatment and clinical cure failure of metritis in dairy cows.

The objective of this study was to evaluate the differences in milk production, reproductive performance, and culling associated with antimicrobial therapy and clinical cure of metritis in dairy cows. In this study, data from 2 randomized controlled trials consisting of 900 Holstein cows from 5 dairy farms in California, Florida, and Texas were used. Cows were examined for metritis (fetid, watery, reddish-brownish vaginal discharge; VD) at 4, 7, and 10 DIM (study d 0). Cows diagnosed with metritis (n = 900) were randomly assigned (regardless of fever) to receive ceftiofur (CEF = 457) or to remain untreated (NT = 443). Clinical cure of metritis was assessed at study d 13 ± 1 based on the visual evaluation of the VD; cows that underwent clinical cure displayed clear, mucopurulent, or purulent discharge (cured = 710), whereas cows with clinical cure failure had persistent fetid, watery, reddish-brownish VD (not cured = 190). The data were analyzed considering antimicrobial treatment, cure status on d 13 ± 1, and their interaction. Risk of pregnancy and culling at 300 DIM were analyzed using logistic regression, time to pregnancy and culling by 300 DIM were analyzed using Cox's proportional hazard, and milk production within 300 DIM was analyzed using ANOVA with repeated measures. Antimicrobial treatment and cure status were included as fixed effects and farm as a random effect in all models. Both randomized trials that generated data used in this study reported a greater risk of clinical cure associated with CEF treatment. Differences in risk of pregnancy at 300 DIM were associated with cure status (cured = 70.9% vs. not cured = 61.7%), but not with antimicrobial treatment or antimicrobial treatment by cure interaction. The risk of culling at 300 DIM was not associated with cure status, antimicrobial treatment, or antimicrobial treatment by cure interaction. Reduced median time to pregnancy was associated with cure status (cured = 134 vs. not cured = 154 d) but not with antimicrobial treatment or antimicrobial treatment by cure interaction. No interaction of antimicrobial treatment by cure status was observed on milk production; however, interactions between antimicrobial treatment, parity, and month of lactation and cure, parity, and month of lactation were observed. Differences in milk production between multiparous CEF and NT cows were observed in the third month of lactation. Conversely, differences in milk production associated with cure status were observed for primiparous and multiparous cows in the first and second months of lactation, whereas only multiparous cows in the eighth, ninth, and tenth months of lactation presented differences in milk production. Clinical cure of metritis was positively associated with milk production and reproduction, regardless of antimicrobial therapy, warranting further investigation regarding selective therapy of metritis.