Evaluating the Effect of Preventative Trimming on Distance from the Sole Surface to the Distal Phalanx Using Ultrasonography for Lameness Prevention in Pasture-Based Dairy Cows

SIMPLE SUMMARY: In pasture-based cattle, it is often suggested that claw trimming, a common lameness prevention practice in housed cows, results in thinner soles over the medium-to-long term. However, there is a lack of data on claw trimming in pasture-based cows. The aim of this study was to measure the effect of trimming on sole thickness in pasture-based cows and evaluate the effect of sole thickness on locomotion scores. Cows were randomly selected and allocated to ultrasound-trimming and ultrasound-non-trimming groups. In May 2018 (at drying off), the ultrasound-measured distance from the external claw sole surface to the pedal bone (distance to the pedal bone) was recorded. Then, trim-group cows were trimmed using the five-step Dutch method to trim the hindlimbs. These procedures were repeated during early lactation (October 2018) and toward the end of lactation (May 2019). The study found that trimming did not affect distance to the pedal bone and that there was no clear effect on the time to increased locomotion scores. The results of this study suggest that in pasture-based cattle, hoof trimming by a professional hoof trimmer using the Dutch method does not alter sole thickness over time. ABSTRACT: One common management strategy used to reduce the risk of lameness is prophylactic claw trimming. However, in pasture-based cattle, there is a concern that the immediate reduction in sole thickness resulting from sole trimming will lead to medium-to-long-term reductions in sole thickness, which may increase the risk of lameness. Nevertheless, there is a lack of data on sole thickness and trimming in pasture-based cows. Therefore, the aim of this study was to evaluate the effect of trimming on sole thickness over the medium-to-long term, as estimated using the ultrasound-measured distance from the external claw sole surface to the distal phalanx (DDP) and of DDP on the interval between calving and increased locomotion scores. A total of 38 cows were randomly selected from a 940-cow spring calving dairy farm in the North Island of New Zealand; 18 were allocated to the ultrasound hoof-trimming group and 20 were allocated to the ultrasound non-trimming group. Starting in May 2018, at the end of the 2017/18 lactation, ultrasound measurements of DDP of the right hind hoof were made on all 38 cows, and the hindlimbs of the trimming group cows were trimmed by an experienced professional hoof trimmer using the five-step Dutch method. This was repeated in October 2018 (early lactation) and May 2019 (late lactation). After calving, the cows were locomotion scored fortnightly until the end of lactation using the 4-point (0–3) scale DairyNZ system. The effect of DDP on the interval between calving and the first locomotion scores ≥1 and ≥2 was assessed using Cox proportional hazards models, and the association between trimming and DDP was explored using linear mixed models. The results suggest that DDP has no effect on the time to locomotion scores ≥1 or ≥2, although the wide confidence intervals of the latter suggest that more data are needed before any definitive conclusions can be drawn. The study failed to find any clinically important impact of prophylactic trimming on DDP. This is likely related to the finding that cows with the highest DDP at the first trimming were identified by the hoof trimmer as those needing the most trimming. The results of this study thus suggest that if the Dutch five-step method is properly applied, it is unlikely to affect sole thickness over the short-to-medium term in pasture-based cattle.