Evaluating the effect of a mid-lactation hoof trimming on lesion prevalence in dairy cows

Introduction
Lameness caused by hoof lesions is an economic and welfare concern in the dairy industry. Hoof trimming is a commonly recommended preventative intervention yet studies indicating appropriate timing and technique for the procedure are limited. The objective of this project was to determine if cows receiving a mid-lactation hoof trimming had reduced lesion incidence at their next scheduled hoof trimming compared to that did not receive a mid-lactation hoof trimming. 

Materials and Methods
This randomized trial occurred on a farm using free-stall housing, recycled sand bedding and a regular HT schedule. This farm was part of a larger study that evaluated the impact of 2 modelling techniques on lesion occurrence at their mid lactation hoof trimming. When cows were evaluated at their mid lactation (90-165 days in milk) hoof trimming for the original study they were enrolled in the current study. Only cows with no hoof lesions or not in need of a hoof trimming due to having overgrown hooves were eligible for inclusion into the current study. Cows were allocated to receive 1 of 3 treatments at their mid-lactation hoof trimming at the time of the original study enrolment. Treatment groups consisted of, 1) odd numbered cows were just restrained and evaluated for lesion (NOTRIM), 2) even numbered cows that were allocated to the same larger modelling technique as in the original study (BIG), 3) even numbered cows that were allocated to the same smaller modelling technique as in the original study (LIT). The presence or absence of lesions was determined at the cow’s next scheduled hoof trimming around the time of drying off. Our main outcome of interest. Using Bayesian analysis with non-informative priors, the odds of having a lesion present at the cow’s next hoof trimming was determined for each of our treatment groups. 

Results
A total of 778 cows were enrolled into the study with 376 in NOTRIM, 190 in LIT and 212 in BIG. Average DIM at enrolment 113 and 556 (71%) of the cows were Holstein with remainder being crossbreds. A total of 208 (27%) did not receive a subsequent hoof trimming. Average DIM of the 570 cows that received a next hoof trimming was 289. At the next hoof trimming 108 (19%) if cows had a lesion. White line disease was the most frequent lesion at next hoof trimming with 12% of cows affected. The odds of a cow having a lesion was 1.4 (95% Credible Interval 0.8-2.2) for cows trimmed in the BIG group, and 1.3 (95% Credible Interval 0.7- 2.0) for cows in the LIT group compared to cows that did not receive a trim. 

Conclusions
Results from our study showed a lack of evidence of mid-lactation hoof trimming reducing hoof lesion prevalence. Our credible intervals showed a wide range of plausible effects ranging from 20-30% lower odds of lesions to a 2.2 higher odds of lesions. Since this study was completed in only 1 herd with 1 hoof trimmer in a high hoof wear environment results from this study might not be generalizable to other types of housing systems. In addition, in our project all cows were evaluated in the hoof trimming chute at 100 DIM and only cows without lesions were enrolled in the study. Herds in high wear environments should only consider not doing mid lactation hoof trimming if they have excellent lameness detection strategies.