LAUSR

The aim of this cross-sectional study was to investigate factors associated with lameness in dairy cows on intensive farms in southern Brazil. Farms (freestall: n = 38; compost-bedded pack: n = 12) having on average 274 (range: 41-901) lactating cows were visited once in 2016 (March to October). Potential risk factors for lameness at the cow, pen and herd levels were investigated through inspection of facilities, examination of cows and the use of data collected on routine management practices. All milking cows on each farm were assessed for gait score and BCS (n = 13,716). Associations between lameness, days in milk (DIM), BCS, parity, and test-day milk yield were investigated in 16 farms with available data (n = 5,301 cows). Mixed-effects linear and logistic regressions were used to model the data. Within-herd lameness prevalence was 41.1% (range: 13.8-64.5, SD = 11.3). First- and second-lactation cows after 120 DIM and older cows after 335 DIM were more likely to be observed lame than early lactation cows. Greater parity and low BCS (≤ 2.75) were associated with increased odds of lameness. Severely lame cows had lower milk yield (on average 1.3 kg/d) than non-lame cows. Freestall dairies using mattresses as stall base had greater within-pen (95% CI: 52-69%) and herd-level (38-57%) lameness prevalence than compost-bedded farms. Higher lameness prevalence was observed on farms having slippery feed bunk alley floors (32-49%) and shortened dry periods (< 60 days: 32-42%). First-lactation pens had lower predicted within-pen lameness prevalence (0-4%) and special-needs pens higher (52-73%) compared with the prevalence observed in compost-bedded fresh-cow pens (19-41%). Freestall pens using sawdust deep-bedding had greater (46-68%) within-pen lameness prevalence, but the prevalence in barns using sand was not different from compost-bedded farms. Given the high lameness prevalence observed in this study, there is a great opportunity for implementation of lameness prevention programs. Providing walking surfaces with high traction that facilitates mobility and using soft and deep-bedded material, such as compost and sand (and avoiding the use of mattresses) may reduce lameness prevalence in the types of dairy farms visited in this study.