Rate of keratinization of the wall segment of the hoof and its relation to width and structure of the zona alba (white line) with respect to claw disease in cattle

Abstract

Abstract Objectives To determine contribution of the wall segment of bovine cattle hoof to horn production, and relevance of structural differences of the wall segment and its horn production rate to claw disease. Design Epidermis and papillary body of the wall segment were examined by mesoscopy, light microscopy, and transmission and scanning electron microscopy. Morphometry of the entire length of the zona alba was examined, and the horn production rate of the wall segment was calculated. Animals Mixed-breed, dual purpose (beef and dairy) cattle of either sex, and young (20 months) Holstein-Friesian beef bulls. Procedure Blocks of a strip of the hoof from the coronary segment to the sole margin, including epidermis and dermis, were prepared for light and transmission electon microscopy. Prepared specimens of the wall-sole border were examined by scanning electron microscopy. Morphometry was performed on the outer, middle, and inner parts of the zona alba structures on unfixed horn specimens of beef bull claws. After removal of the zona alba specimens, the claw was removed and the proximodistal extent of the epidermal leaflets was measured and analyzed statistically. Results Horn production increased in the distal half of the wall segment, was greatest at the wall-sole border, and highest above the abaxial end of the zona alba. High horn production resulted in an incompletely keratinized, softer horn. Conclusions and Clinical Relevance High horn production at the zona alba increases susceptibility to vascular disturbance. Claw dyskeratoses appear first in areas of high horn production, areas which are also subject to a greater frequency of claw lesions. (Am J Vet Res 1996;57:444–455)