Pathophysioloy of claw horn lesions in dairy cows

Background: A review of the pathophysiology of horn lesions of hoof in dairy cattles.
Objective: To describe the the horn tissue growth, the role of molecular, cellular, and pathological changes in horn lesions of hoof, and the factors affecting these lesions.
Methods: A review study using sources published in the field of horn tissue growth and horn lesions of bovine hoof in reputable national and international books and journals.
Results: Horn deterioration of bovine hoof is a feature of lesions in the hoof, which in extreme circumstances are manifested in ulceration of sole. Claw horn is composed primarily of keratin proteins, whose distribution is altered at lesion sites in the hoof sole. Normal horn of bovine hoof tissue develops through a process of intracellular keratinization, microfilament synthesis and cross-linking, protein and lipid deposition around the plasma membrane, and finally cross-linking of envelope proteins. Cells of the innermost basal cell layer enter the cell cycle to generate progeny cells that translocate to the suprabasal layers. Growth activity in suprabasal cells becomes progressively restricted with the onset of programs of differentiation until the cells permanently abort the cell cycle. Terminally differentiated cells of the suprabasal layers of epithelium no longer grow but differentiate into heavily keratinized, cornified cells of the outermost suprabasal layers. Important factors that affect the health of claw horn tissue include nutrition, hygiene, management, and genetic and breeding contexts.
Conclusion: The lack of knowledge about biologic events orchestrating normal growth, differentiation, and maturation of claw horn tissue creates challenges for understanding claw horn production during periods of health and disease.