The locomotion of dairy cows on floor surfaces with different frictional properties.

The locomotion of dairy cows was evaluated on floors with a smooth epoxy resin surface or with a surface-applied bauxite aggregate of mean diameter 0.5, 1.2, or 2.5 mm (coefficients of static friction, mu 0.35, 0.42, 0.49, and 0.74, respectively). Locomotion was recorded as cows walked to receive a food reward. Cows on the floor with least friction walked rapidly (0.85 m/s), with frequent, short steps. At the start of the supporting phase the upper limbs were more vertical. Joint arcs during this phase were reduced. Cows on 0.5-mm aggregate also walked rapidly (0.84 m/s); they had the least vertical limb angles and long steps but held the hoof more vertical, probably to offset any increased slip risk. On floors with larger aggregate, cows decreased speed and step frequency but maintained long steps, keeping their upper forelimbs more vertical to reduce the supporting limb phase. It is concluded that on a low friction floor (mu < 0.4), cows walk quickly with frequent, short steps. As mu increases to 0.5, step length increases and the number of steps decreases to maintain speed at increased friction, producing an optimal coefficient of friction between 0.4 and 0.5. Further increases in mu may increase the hanging limb phase at the expense of the supporting limb phase, to reduce friction, while maintaining a long stride to expedite arrival at the reward.