A randomized trial to evaluate the effect of a trace mineral premix on the incidence of active digital dermatitis lesions in cattle.

A balanced, parallel-group, single-blinded randomized efficacy study divided into 2 periods was conducted to evaluate the effect of a premix containing higher than typically recommended levels of organic trace minerals and iodine (HOTMI) in reducing the incidence of active digital dermatitis (DD) lesions acquired naturally and induced by an experimental infection challenge model. For the natural exposure phase of the study, 120 healthy Holstein steers 5 to 7 mo of age without signs of hoof disease were randomized into 2 groups of 60 animals. The control group was fed a standard trace mineral supplement and the treatment group was fed the HOTMI premix, both for a period of 60 d. On d 60, 15 steers free of macroscopic DD lesions were randomly selected from each group for the challenge phase and transported to an experimental facility, where they were acclimated and then challenged within a DD infection model. The same diet group allocation was maintained during the 60 d of the challenge phase. The primary outcome measured was the development of an active DD lesion greater than 20mm in diameter across its largest dimension. No lesions were identified during the natural exposure phase. During the challenge phase, 55% (11/20) and 30% (6/20) of feet were diagnosed with an active DD lesion in the control and treatment groups, respectively. Diagnosis of DD was confirmed by histopathologic demonstration of invasive Treponema spp. within eroded and hyperplastic epidermis and ulcerated papillary dermis. All DD confirmed lesions had dark-field microscopic features compatible with DD and were positive for Treponema spp. by PCR. As a secondary outcome, the average DD lesion size observed in all feet was also evaluated. Overall mean (standard deviation) lesion size was 17.1 (2.36) mm and 11.1 (3.33) mm for the control and treatment groups, respectively, with this difference being driven by acute DD lesions >20mm. A trend existed for the HOTMI premix to reduce the total DD infection rate and the average size of the experimentally induced lesions. Further research is needed to validate the effect of this intervention strategy in the field and to generate prevention and control measures aimed at optimizing claw health based on nutritional programs.