Lameness during the dry period: Epidemiology and associated factors

Lameness has been extensively studied in lactating cows, whereas few studies have reported on lameness during the dry period. We conducted a prospective longitudinal study to describe the epidemiology of lameness during the dry period and to identify risk factors associated with onset, cure, and chronic cases of lameness. A total of 455 cows from 6 freestall commercial dairy farms were enrolled at 9 wk before calving and gait scored weekly until calving using a 5-point scale. A subset of cows was also followed fortnightly after calving to measure the association between lameness during the dry period and lameness during early lactation. Body condition score (BCS) was assessed in a 5-point scale using increments of 0.5. Hoof-trimming records, parity, and previous lactation milk production were retrieved from farm's database. Cows were considered sound when 2 consecutive scores were ≤2 and lame when 2 consecutive scores = 3, or any assessment with score >3; when in a sequence of scores only one score = 3 (or ≤2), the cow was considered sound (or alternatively lame). Following this lameness definition, we derived weekly lameness status for each cow and calculated the number of new cases of lameness, the number of cure cases and the number of chronic cases. The incidence rate of lameness cases during the dry period was 8.2 lameness cases/100 cow per wk, whereas cure rate was 7.1 cure cases/100 cow per wk; at the end of the dry period 50% of cows had developed lameness and 36% were cured. Multilevel logistic regression models using farm as random effect were fitted to assess (1) the association between being lame in wk 2 or 8 postcalving with being lame in the last week precalving, (2) risk factors for lameness onset, (3) risk factors for lameness cure, and (4) risk factors for chronic lameness. Cows that were lame in the week immediately before calving were more likely to be lame in wk 2 and 8 after calving. We found that the interaction between parity and hoof-trimming before dry-off was associated with lameness onset; primiparous cows that were trimmed before dry-off had lower odds of developing lameness, whereas the opposite was found for multiparous cows. The same interaction was also associated with the odds of chronic lameness. Cows that were diagnosed with noninfectious hoof lesions compared with cows that were not diagnosed with hoof lesions before dry-off, and cows that had BCS <3 compared with cows with BCS 3.0 to 3.5 at dry-off had higher odds of chronic lameness. Conversely, primiparous cows and cows with BCS 3.0 to 3.5 had higher odds of curing lameness during the dry period. Our results suggest that the dry period may be a period of high risk for lameness development and that hoof-trimming before dry-off may not be effective for all cows.