Efficacy of salicylic acid in the treatment of digital dermatitis in dairy cattle.

Digital dermatitis (DD) is one of the most important causes of lameness in dairy cattle worldwide. The objective of this study was to evaluate the efficacy of salicylic acid in the treatment of the disease. A total of 201 DD lesions from 173 cows from four commercial dairy herds were evaluated at day 0 during routine hoof trimming and were allocated into two groups, namely, a control group given chlortetracycline spray, and a treatment group given 10 g of salicylic acid powder applied topically within a bandage. Pain, lesion size and clinical appearance (scored M0 to M4) were evaluated on days 3, 14 and 34 post-treatment. A change to M0 was defined as healing, while changes of M2 or M4 to M1 or M3 were classified as clinical improvements. Healing rates did not differ significantly between treatment groups at days 3 and 14. By day 34 the healing rate was fivefold better (P=0.01) for the treatment vs. the control group, with healing rates of 13.6% and 3.1%, respectively. By day 3, the rate of improvement was 2.5-fold better (P=0.02) for the controls. By day 34 the overall positive effect (i.e. healing and improvement) was 1.75-fold better (P=0.05) for the treatment group. Lesions from the control group were 2.2 times more likely (P=0.09) to have a pain score equal to 2 by day 14. The proportion of lesions getting smaller by days 14 and 34 was 2.5 times higher (P<0.08) for the treatment vs. the control group. The findings suggest salicylic acid should be considered as an alternative to chlortetracycline for the treatment of DD as it appears more efficacious and would assist in reducing antibiotic use.