The bovine claw is as well organized as an automobile independent suspension system

Introduction
About a hundred years ago, the mass production manufacturing technique for automobiles made progress in leaps and bounds. An independent suspension of an axle was also developed at that time, and the driving performance and environment improved drastically. Upon considering the structure of the bovine claw, the movement of medial and lateral digits are completely functioning as an independent suspension. First, the alignment of the bovine P1, P2, and P3 is not straight like those of horses. They are zigzagged and articulated by ginglymus, consequently, they can work as suspensions individually. Second, each connection from pedal bone to the metatarsal and metacarpal bones, which play the axle of the automobile, firmly joins with a cruciate ligament. The pivot of the axle is the fetlock joint. So the quarter of the claw tend to wear more than the other parts. Specifically, medial claws become narrower and tilt axially in many cases. 

Materials and Methods
Thinking that the claw is an independent suspension, the digital axis is set to each of the medial and lateral claws besides the center axis that is the ideal line running center of the metatarsal. The digital axis is perpendicular to the floor when the weight bearing surface is parallel to the corium. The inclination of the weight bearing surface is determined by the millefeuile hypothesis. We investigated 10,625 hind left feet of Holstein cows which were trimmed in usual visits in 2018. We checked them in the air with a handle of hoof knife. Following 5 combinations of axes the degree they are parallel to the center axis or declined more than 5 degrees were recorded. A: both axes are parallel to the center axis. B: the medial axis is declined axially and the lateral axis is parallel to the center axis. C: the lateral axis is declined axially and the medial axis is parallel to the center axis. D: both axes are declined axially. E: abnormal results

Results
A 453(4.3%) B 9707(91.1%) C 223(2.1%) D 85(0.8%) E 157(1.5%) This number includes 135 young heifers less than 26 months, and all of them were in the category B.

Conclusions
Usual hind claws are imbalanced, large lateral small medial. Small medial claws have to get enough height to balance large lateral claw. The corium parallel trimming method can be one of the methods used to maintain the balance of the claws.