Risk factors for dirty dairy cows in Norwegian freestall systems

Cow cleanliness is important for ensuring hygienic milk production and the well-being of dairy cows. The aim of this cross-sectional field study was to describe cow cleanliness in freestall-housed dairy herds and to examine risk factors related to thigh cleanliness. Cow cleanliness (n=2,335), management-related variables (e.g., ventilation and use of sawdust-bedded stalls), and housing-related variables (e.g., freestall design and number of cows per stall) were recorded in 232 Norwegian freestall-housed dairy herds. Cleanliness was scored on a 4-point scale ranging from clean (1) to very dirty (4). The cows were relatively clean on the udder and belly, dirtier on thigh and the rear part of the body, and dirtiest on the legs, with cleanliness scores (mean ± SD) of 1.64±0.62, 1.62±0.65, 2.02±0.75, 1.77±0.58, and 2.30±0.59, respectively. With dirty thighs as the response variable, several variables were tested in a logistic regression mixed model and with repeated measurements within herd and cow. A high number of cows per freestall [odds ratio (OR)=3.45], no use of sawdust as bedding (OR=3.24) versus use of sawdust, and a low-positioned (<0.85 m above stall floor) upper head rail "enclosing" the front of the stall (OR=1.42 to 2.13) versus a position >0.85 m were all risk factors for dirty thighs on the cows. Furthermore, liquid manure (score 2) versus more consistent manure (score 1; OR=1.66) and less tame cows (score 2) versus tame cows (score 1) were associated with an increased risk of dirty thighs (OR=1.24). The cleanest cows were associated with indoor temperatures in the range from 10 to 15°C. For each 10-percentage-unit increase in relative air humidity, the risk of dirty thighs increased (OR=1.32). Freestalls with a construction hindering normal lying, rising, and standing movements should be avoided. Furthermore, focus is needed on indoor climate and manure consistency to obtain cows with clean thighs.