Characterizing grooming behavior patterns and the influence of brush access on the behavior of group-housed dairy calves

Group housing allows for dairy calves to perform social grooming behavior; however, the use of mechanical brushes may influence how calves groom themselves and others. Our objectives were, first, to characterize the bout characteristics of brush use, self-grooming, and allogrooming in calves and, second, to evaluate the effects of access to a rotating brush on grooming behavior. Holstein heifer and bull calves (n = 32) were group-housed (4 calves/group) at 2 wk of life (17 ± 3 d of age; mean ± standard deviation) and followed to wk 7 of life. Pens were assigned to receive either a rotating brush (BR; n = 4 pens) or no brush (CON; n = 4 pens). Behavior was recorded continuously for 12 h for 2 focal calves/pen on 2 d during wk 4, 6, and 7 of life. We performed a bout analysis by fitting a mixture of normal distributions to the log₁₀-transformed frequency distribution of the intervals between recorded periods of behavior. We calculated bout criteria for brush use (125.9 s), allogrooming (125.9 s), and self-grooming (a mixture of 3 normal distributions provided the best fit for these data, providing 2 bout criteria: a shorter (micro) bout criterion of 50.1 s and a longer (macro) criterion of 1,000 s). Brush use was consistent across weeks, and calves used the brush for 20.5 ± 6.1 min/12 h observation period, in 31.1 ± 1.7 bouts (mean ± SE). The frequency and duration of allogrooming bouts did not differ between treatments and across time. The BR calves tended to self-groom more than CON calves (16.3 vs. 14.3 min/12 h; BR vs. CON; SE = 0.68), and time spent self-grooming decreased across weeks. The frequency and duration of self-grooming micro bouts did not differ between treatments, but BR calves had shorter, more frequent self-grooming macro bouts (10.58 vs. 9.46 bouts; BR vs. CON; SE = 0.24). In summary, we determined that bout criteria could be fitted to grooming behaviors, which may be useful when characterizing these behaviors in future work, and that providing access to a rotating brush influenced self-grooming behavior in group-housed calves.