[Formalin foot baths in the prevention of interdigital dermatitis in cattle]

Formalin (= approximately 35 per cent formaldehyde) foot baths are used with variable success to prevent interdigital dermatitis, eczema of the interdigital skin accompanied by secondary destruction of the bulb horn. Experimental studies were done in vivo and in vitro to determine the significance of the temperature and concentration of the formalin solution and the method of bathing (standing in a bath for sixty minutes or walking through a bath, in which case each foot is immersed twice in the solution). The results show that a low temperature of the bathing solution (10 degrees C), which theoretically produces poor disinfection (Table 3), does not necessarily imply inadequate disinfection in actual practice (Table 4) as the solution will adhere to the interdigital skin for about thirty minutes (Table 2) and very rapidly will acquire the temperature of the skin (20 degrees-30 degrees C, Table 1). Therefore contact between the interdigital skin and grass, mud, dung and so on has to be prevented for the first thirty minutes after bathing. The more intensive contact between formalin and skin in a stationary foot bath offers advantages over the pass-through bath (Table 4). When a 3 percent formalin solution in a pass-through bath fails to produce satisfactory results, a 5 percent solution may be used. This concentration will result in more effective disinfection (Table 4); higher concentrations may cause skin lesions. Repeated daily disinfection does not produce further reduction of the bacterial flora on the interdigital skin to a significant degree (Table 5). In addition to the disinfecting effect, the hardening effect on the interdigital skin may be of importance.