Spot treatment, not pit treatment: Evaluating claw contact time of a spray product under field conditions

Introduction
Lameness in dairy cattle has a major impact on health, welfare and production. This makes it one of the most important endemic diseases in dairy cattle (Huxley, 2013). Dairy farmers traditionally use foot baths to prevent hoof problems. However, the efficacy of footbaths is debatable as it depends on the transfer of the topical antibacterial agent to the foot and its contact time with the claw and adjacent skin (Cook et al., 2012). After a certain number of passages, footbaths are heavily polluted by manure. Because lame cows have the slowest walking speed, they will often pass through a polluted footbath. Additionally, a large part of the footbath content is spilled out of the bath and is thereby not reaching the correct spot on the feet of the cows. Eventually, the remaining chemical in the footbath is poured into the pit, which may contribute to ecotoxicological problems (Holzhauer et al., 2012). A new ready-to-use spray (Intra Hoof-fit Spray) allows every cow to be treated with fresh product regardless of their walking speed. The product can be used in the prevention of hoof problems and is based on equal parts of chelated copper and chelated zinc. It can be applied using e.g. a low-pressure sprayer, automatic sprayer or robot sprayer, and has a strong adhesive power to the claws providing a long contact time, which was evaluated in this trial under field conditions. 

Materials and Methods
This study was performed on a Dutch dairy farm with 92 dairy cows. The disinfection protocol of this dairy farm did not include foot bathing. The feet of 6 dairy cows were sprayed (t=0) for 2 seconds using a low pressure sprayer, while the animals were secured to the feeding fence. Swabs from the feet were taken on 3 time points (t=1, t=3 and t=6 hours) while the animals were in a claw trimming box, and the last swabs were taken on the 4^th time point (t=9 hours) in the milking parlor. In between measuring moments, the cows were able to express their natural behavior under regular farm conditions in the house. Swabs were taken by a standardized method with a cotton swab and contained in a tube filled with 10 ml demineralized water. The samples were filtered over a 0.45 μm filter and the presence of copper was measured at a wavelength of 510 nm with a 4210 MP Atomic Emission Spectroscopy (AES) from Agilent Technologies. From an analytical point of view, copper was measured instead of zinc. Results were corrected for the average weight of the samples. […]