The Comparative Anatomy of the Metatarsal Foot Pad in Eight Species of Birds of Prey and Owls with Regard to the Development of Pododermatitis

Pododermatitis (bumblefoot) occurs commonly in birds of prey and owls and shows species-specific differences in its prevalence, especially between falcons and hawks. The development of the disease is particularly associated with circulatory disorders of the feet. To compare the blood vessel supply of the foot sole, especially the metatarsal foot pad, macroscopic dissections including intravascular injection of latex, contrast µCT scans with barium sulphate, corrosion casts (epoxy resin), and histological examinations of the skin were performed in eight avian species. The main supplying artery of the metatarsal pad, the pulvinar artery, originated from the medial digital artery of the first toe. This main pulvinar artery showed a rather vertical course towards the sole surface, subsequently encircling the metatarsal pad like a basket in falcons and owls, whereas a rather horizontal straight course was observed in northern goshawks and common buzzards. Organized fat tissue was present in the subcutis as the basis for the metatarsal pad only in falcons and owls. The dermis of the metatarsal pad showed a well-developed papillary layer and prominent dermal and subdermal vascular networks in all species examined. The observed differences were discussed regarding both the species-specific prevalence and the etiology of bumblefoot.