**Acknowledgements**

*Veterinary Anatomy and Physiology*

mens from claws with chronic laminitis.

the cow is in standing posture or in locomotion.

led to an increased capillary network, could be a response to inflammatory reaction occurring in laminitis [14]. Enlarged veins seen only in chronic laminitis, which remained widely open appeared like venous dilatation rather than thickening of the

Oedema that was seen in the corium and in the connective tissue of the sole has been reported previously [6]. It occurs as a result of rising capillary pressure together with post-capillary resistance, which enhances transvascular fluid seepage followed by increased pressure within the tissues. Digital venous constrictions are thought to be the initial step in these processes [39]. Subsequently, oedema expands the corium, which causes pain that leads to lameness seen in laminitis [6, 44]. Although chronic degenerative change in the bovine corium of the claw has been reported in chronic laminitis previously [45], the disruptive connective tissue damage particularly involving fibroblasts has not been reported previously. This disruptive damage is probably a degenerative change associated with enzymatic action of matrix metalloproteinases (MMPs) and gelatinolytic protease known as hoofase [46]. It may also be a biochemical alteration in the connective tissue [20]. The degenerative disruption of the connective tissue was observed only in speci-

Disruption of the dermal-epidermal junction is an invariable finding in subclinical and chronic laminitis owing to compromised microvasculature of the corium, which causes nutrients and oxygen to be diminished to the extent of not reaching the epidermal cells. This causes breakdown of the stratum germinativum in the epidermis, the corium becomes degenerated and eventually a breakdown in dermalepidermal junction that results in separation between the stratum germinativum and the corium [44]. Spongiosis and hyperplasia of the epidermis have not been reported previously. Both of these histological changes occurred in subclinical as well as in chronic laminitis. Probably, they are due to inflammation triggered by pressure irritation on the soft tissues located between the pedal bone and the horn of the sole after the claw comes into contact with the hard treading surface when

Previous studies have shown that laminitis and laminitis-related claw disorders have various cow-level and farm management-level risk factors [2, 6–8]. Although the cows whose claws were used in this study had been pregnant several times, the number of pregnancies and the stage of lactation were not ascertained from the zero-grazing units in which they were kept. It would therefore be recommended that further study be conducted relating macroscopic, radiographic and histopathologic findings on the claws with number of parities, state of pregnancy and stage of lactation of the cows. This will reveal the nature of correlation between these factors, thus indicating the factors exacerbating morphological changes on the dairy

The study concluded that claw disorders are prevalent in dairy cows kept under zero-grazing system. The most commonly occurring macroscopic disorders are sole bruising (erosion), claw deformities, heel erosion, double soles, both subclinical and chronic laminitis and white line separation. The radiographic changes found in the claws were mainly associated with chronic laminitis. These occurred on the pedal bone and included dilated vascular channels, irregular bone margins, narrowing of the bone towards the apex and osteolysis. The histopathologic changes were common in the corium of both subclinical and chronic laminitis claws, which included mainly changes in the vasculature such as venular wall damage, arterial

cow claws. This should also include correlation with the seasons of the year.

wall. This feature has not been described previously in laminitis.

**52**

**6. Conclusions**

We are grateful to the University of Nairobi Deans Committee for provision of funds to carry out this research. We thank the Chairman of the Department of Clinical Studies for allowing us the use of Departmental laboratory and imaging facilitation to carry out this research.
