The stall-design paradox: neck rails increase lameness but improve udder and stall hygiene.

Housing conditions for dairy cows are thought to affect lameness, but almost no experimental work has addressed this link. The aim was to assess the effect of one feature of free-stall design, the position of the neck rail, testing the prediction that cows will be more likely to become lame if using pens with the neck rail positioned such that it prevents standing fully inside the stall. Cows (n = 32) were housed in 8 pens. Treatments were tested using a crossover design; treatments were allocated alternately to pens at the beginning of the experiment and switched halfway through the 10-wk experiment. Cows spent 27 +/- 3 min/d standing with all 4 feet in stalls with less restrictive neck rails. In contrast, cows averaged just 1 +/- 3 min/d when the neck rail was positioned restrictively. Cows spent less time standing with only the front 2 feet in the stall with less restrictive neck rails (33 vs. 49 +/- 6 min/d). Gait scores improved when cows were kept in the less restrictive stalls and worsened when cows were kept in pens with the restrictive neck rail (median score 2.5 vs. 3.5 after 5 wk on treatment). Of 13 new cases of lameness, 11 occurred in pens with the restrictive neck-rail position. Similarly, of the 16 new cases of sole lesions, 15 occurred during the period when cows were housed in pens with a restrictive neck rail. Stalls with the neck rail positioned less restrictively had higher contamination scores than stalls with the restrictive neck rails (3.7 vs. 0.4 +/- 0.2), and cows using those stalls had dirtier udders and longer teat-cleaning times (8.3 vs. 7.0 +/- 0.2 min for 12 cows). This study provides the first experimental evidence that aspects of stall design can reduce the risk of lameness and hoof disease. The results illustrated that changes in design that resulted in improvements in cow comfort and hoof health came at the expense of cow and stall cleanliness.