Associations between herd-level factors and lying behavior of freestall-housed dairy cows.

Our objective was to investigate the associations between herd-level factors and lying behavior of high-producing dairy cows housed in freestall barns. Lying behavior of approximately 40 focal cows in one high-producing pen was monitored on each of 40 farms in the northeastern United States (NE) and 39 farms in California (CA). All cows within the pen were gait scored using a 1-to-5 scale to calculate the prevalence of clinical lameness (score ≥3) and severe lameness (score ≥4). Facility and management measures, including stall design, bedding, and flooring type within the pen, were collected. Herd-level factors associated with daily lying time, standard deviation (SD) of daily lying time, frequency of lying bouts, and lying bout duration at the univariate level were submitted to multivariable general linear models. In the NE, daily lying time increased with the use of deep bedding (estimate = 0.80±0.31h/d) and as average days in milk (DIM) of the focal cows increased (estimate = 0.08±0.04h/d for a 10-d increase in DIM). The SD of daily lying time decreased as stall stocking density increased (estimate = -0.08±0.03h/d for a 10% increase), and increased with the presence of rubber flooring in the pen (estimate = 0.16±0.08h/d) and percentage of stalls with fecal contamination (estimate = 0.04±0.01h/d for a 10% increase). Frequency of lying bouts decreased (estimate = -1.90±0.63 bouts/d) and average bout duration increased (estimate = 15.44±3.02 min) with the use of deep bedding. In CA, where all farms used deep bedding, daily lying time increased as average DIM of the focal cows increased (estimate = 0.08±0.03h/d for a 10-d increase). The SD of daily lying time decreased when feed was delivered more than once per day (estimate = -0.24±0.08h/d). The percentage of lame cows was correlated with the percentage of stalls with fecal contamination (r=0.45), which in turn was associated with fewer (estimate = -0.25±0.06 bouts/d) and longer lying bouts (estimate = 1.85±0.39 min/d). These findings suggest that lying time be interpreted in conjunction with variability in lying time and bout structure and in context with lameness prevalence, production parameters, and facility characteristics.