Lameness in the dairy cow results in large financial losses to the industry and severely compromises the welfare of the cows affected. A large proportion of lameness involves haemorrhage and lesions of the solar horn of the hoof. Deterioration of hoof horn quality may involve inadequate keratinisation, with differences in the amount of specific keratins present in the horn. Few studies of the keratin composition of solar horn have been carried out. The present study examines specifically the expression of the type I, acidic cytokeratin 9 (CK9). since this protein appears to be a major constituent of hardened epidermal structures. In human epidermal studies, CK9 has only been identified in the calloused palmar and plantar sites (Langbein et al, 1993). A comparable cytokeratin has been demonstrated in the epidermis of the bovine heel pad, but not at other body sites studied (Knapp et al, 1986). CK9 has not previously been reported in the solar horn.

Bovine hoof soles from adult cows were obtained from abattoirs. Samples of cornified Stratum comeum material from below the pedal bone (the commonest site of solar lesions) were taken and the proteins extracted in 8M urea.