Stationary brush use in naive dairy heifers

Weaned dairy heifers are often housed in environments with few appropriate outlets for grooming or oral manipulation. Our objective was to characterize brush use by naive heifers, including patterns over time. In phase 1, groups of 4 heifers (n = 13 groups, 146.4 ± 9.1 d old, mean ± standard deviation; SD) were introduced to a bedded pack pen with 4 wall-mounted brushes (25.4 × 6.0 cm with 3.8-cm-long bristles). On d 1, 2, and 6 of exposure, continuous video recordings were used to observe 2 focal heifers per group for brush use (oral manipulation, grooming, and the sum of total brush use; all averaged at the group level). Latency to use a brush upon entering the pen was 3.4 ± 4.9 min (mean ± SD; range: 0.1 to 17.8 min among individuals). Heifers used the brushes for oral manipulation (39.7 ± 17.5% of brush use, mean ± SD) and grooming (60.3 ± 17.5%), primarily of their heads (89.9 ± 5.4% of grooming). In phase 2, heifers were moved in pairs (n = 13 pairs/treatment) to freestall pens either with (brush treatment) or without (control) brushes mounted inside the stalls for the first 5 d of phase 2 (d 8-12 of the study); on the last day (d 13 of the study), brushes were provided in both treatments. On d 8 (brush treatment) and 13 (both treatments), one focal heifer/pen was recorded for the same behaviors as in phase 1. Linear mixed models were used to evaluate brush use patterns across days (phase 1: d 1, 2, and 6; phase 2 brush treatment: d 8 vs. 13) and between treatments on d 13. In phase 1, brush use was greatest on d 1 [45.9 min; 95% confidence interval (CI): 33.2-63.3 min, back-transformed from natural-log values], decreased on d 2 (25.0 min, 95% CI: 18.4-34.0 min), but then remained steady until d 6 (21.0 min, 95% CI: 15.4-28.5 min); the initial reduction in total brush use was due to changes in grooming, but oral manipulation remained relatively static. In phase 2, heifers in the brush treatment showed similar usage on d 8 versus d 13 (3.8 vs. 3.7 min, 95% CI: 1.9-6.8 vs. 1.9-6.5 min). Compared with heifers with continuous brush access on d 8-12, those in the control treatment showed more brush use on d 13, both for oral manipulation (6.6 vs. 2.5 min, 95% CI: 3.8-11.1 vs. 1.3-4.5 min) and grooming (3.5 vs. 1.2 min, 95% CI: 1.9-5.7 vs. 0.5-2.3 min). Our study is the first to characterize stationary brush use in weaned dairy heifers. We conclude that, despite lacking previous experience, heifers use brushes for both grooming and oral manipulation.