The periodic trimming of the long hairs growing at the distal end of the tail -switch trimming- is humane alternative of tail docking. The purpose of this study was to determine the influence of switch trimming on somatic cell count (SCC), California mastitis test (CMT) and udder cleanliness of lactating cows in a free-stall dairy farm. In the present study, 219 healthy, pregnant Holstein cows were enrolled. All cows were randomly allocated to either trimmed (T) (n=107) or control (C) groups (n=112) prior to entering the calv-ing pen. The long hair in the tail switch of the cows enrolled in group T was removed completely by a hair clipper machine, while the tail hair of the animals enrolled in group C remained intact. After two months, all studied cows were evaluated for udder cleanliness and health. Udder cleanliness scores (UCS) were sig-nificantly associated with switch trimming of the tail (P=0.0129). Both trimmed and control cows showed significant difference in UCS of 2 and 3 (P≤0.05), though the difference in other UCS was not significant. No significant difference (P=0.41) in SCC between groups was identified. Comparing the CMT scores of front, rear, or all udder quarters showed that the frequency of a CMT score of 0 in group T was significantly higher than in group C (P≤0.05). Reversely, the frequencies of Trace and 2 scores of CMT for rear and all udder quarters in the control group were significantly higher than the group T (P<0.05). The results of this study show that switch trimming may be suggested to improve cleanliness and udder health of dairy cows in free-stall housing systems.
