Comparison of the efficacy of a commercial footbath product with copper sulfate for the control of digital dermatitis

Digital dermatitis (DD) is the most prevalent foot lesion affecting dairy herds worldwide. Its implications include production losses and decreased animal welfare. Footbathing is the most common herd-level prevention strategy for DD. Because many common footbath products have negative environmental and health consequences, replacement products expected to have improved safety but equal efficacy are being developed. Therefore, the aim of this study was to evaluate the efficacy of a new quaternary ammonium-based commercial footbath product (QAC) for reducing the prevalence of active DD lesions compared with an industry standard (copper sulfate; CuSO4) and typical on-farm footbath practices. A controlled intervention trial was conducted on 19 Alberta dairy farms over 12 wk, with 9 farms allocated to the QAC group (1% QAC daily, 5 d/wk), 5 to the CuSO4 group (5% CuSO4 daily, 5 d/wk), and 5 to a noninterference group (maintained typical footbath practices). A total of 22,285 observations on 3,465 lactating cows were assessed for DD lesions and leg cleanliness in the milking parlor. Five farms discontinued use of the QAC product for various reasons. Noninferiority analysis was used to assess QAC ability to decrease the proportion of cows with 1 or more active DD lesions compared with CuSO4 after 6 wk. Multilevel logistic regression models for repeated measures were used to evaluate efficacy of QAC compared with CuSO4 and noninterference farms in reducing the prevalence of active DD lesions at the foot level over 12 wk. The noninferiority analysis determined that the proportion of cows with 1 or more active DD lesion decreased 2.19 (95% CI: 1.39-3.46) times less after 6 wk of study on the QAC farms compared with CuSO4 farms, making QAC inferior to CuSO4. The multilevel logistic regression models determined that the proportion of active DD lesions increased in the QAC herds, whereas this proportion decreased in the CuSO4 and noninterference herds over 12 wk. Additionally, cows in mid- and late-lactation had a higher odds of having active DD compared with fresh cows. Older cows (parity 3 and ≥4) had a decreased odds of active DD compared with first-parity cows. At the farm level, a higher baseline active DD prevalence resulted in increased odds of active DD; however, this did not modify the effect of treatment or week of study. We concluded that QAC was inferior to CuSO4 and typical on-farm footbath practices, and further development of novel footbath products is required to develop an ideal alternative.