2017 Volume 70 Issue 3 Pages 155-158
Screw claws are characterized by the abnormal precipitous slope of the abaxial hoof wall toward the axial side because the faster growth of the hoof wall on the abaxial side than on the axial side. The deformation allows the rolling of the abaxial hoof wall under the surface of the sole. Such claws ground and load with the outer surfaces of the rolled abaxial hoof wall. Computed tomographic (CT) examinations of cadaverous specimens obtained from seven female Holstein cows with screw claws revealed that these cows had sharp shapes due to osteolysis within the apex of the distal phalanx (3/7: cumulative number of cows/total cows), bony developments within the proximal and middle phalanx (2/7), fractures in the distal phalanx (2/7), bony developments within the distal phalanx (2/7), and deformation in the basal surface of the distal phalanx (1/7). Such bony changes within the phalanxes of the cows with screw claws may occur due to the abnormal mechanical loads on the proximal and middle phalanxes as well as the distal phalanx based on chronic unusual posture.