September 26, 2015 | Veterinary Record | 319 Letters Letters The minimum values for sole thickness provided, and hence derived claw length, allow operators to use claw lengths greater than our recommendations, yet we would not advocate shorter lengths. We fear that Mr Blowey may have misinterpreted our minimum figures as ‘target’ or ‘average’ values; this was not our intention and we thank him for the opportunity to clarify this point. In the absence of data defining optimum claw length for specific situations, our minimum recommendations (90 mm) provide a safe guide for the majority (estimated 96 per cent) of Holstein claws; we suggest they should be considered minimum safe values. We believe the key message from the paper should be how woefully inadequate a claw length recommendation of 75 mm (minimum or average) would be if measured from the proximal tip of the wall horn in the modern Holstein. Our minimum claw length recommendations were based on a sole thickness of at least 5 mm, specifically to highlight this. For toes trimmed to a point, our data suggest that to mitigate overtrimming of 10 claws, only 11 would need to be trimmed to no less than 90 mm instead of 75 mm (absolute risk reduction = 91 per cent). Mr Blowey is correct that a claw length of 97 mm is required if the target sole thickness is 10 mm. To mitigate overtrimming of a further 10 claws, 250 more claws would need to be trimmed to no less than 97 mm instead of 90 mm (absolute risk reduction = 4 per cent). Therefore, when adjusting for a minimum sole thickness of 10 mm, the impact in the population is likely to be small, compared with a sole thickness of at least 5 mm. We also highlighted that the anatomical landmarks for defining the starting point of measurement at the coronary band (a relatively broad structure) are poorly defined in the literature and current training materials. We accept that operators using a slightly more distal landmark will require shorter lengths and this may well explain some of the variation in recommendations which currently exists. We selected the more proximal landmark again to ensure our recommendations constitute minimum safe values. The majority of variation in claw length between cows remained unexplained, and further work is needed to identify optimal dimensions since one size does not fit all. This may have limited marginal benefit compared with minimum recommendations alone, if these are correctly applied. The primary aim of our work was to assist less experienced operators in applying safe foot trimming protocols on farm. We would ask that all experienced operators and opinion leaders consider our findings when they are undertaking training and updating reference materials, to optimise safe foot trimming practices. We are currently developing resources to assist with the application of our findings in the field. Variations in the anatomical landmarks used for measurement, sole thickness, toe angle and trimming technique (pointed toe or step) will be incorporated into these tools. Simon Archer, Reuben Newsome, Harry Dibble, Craig Sturrock, Mizeck Chagunda, Colin Mason, Jon Huxley, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire LE12 5RD e-mail: simon.archer@nottingham.ac.uk doi: 10.1136/vr.h5142 Reference ARCHER, S.C., NEWSOME, R., DIBBLE, H., STURROCK, C. J., CHAGUNDA, M. G. G., MASON, C. S. & HUXLEY, J. N. (2015) Claw length recommendations for dairy cow foot trimming. Veterinary Record doi 10.1136/vr.103197 Simon Archer and others comment: We would like to thank Mr Blowey for his constructive response to our open access paper; we entirely agree that it would be preferable to trim each individual cow’s foot optimally. The minimum claw lengths we presented incorporate expected variation, and are intended as a guide that is applicable to most cows.