Anatomy of Hereditary Bovine Syndactylism. I. Osteology

Abstract

Osteologic anomalies that distinguish externally 1) normal overlap sy/sy cattle from +/sy and +/+ animals; 2) normal +/sy and +/+ animals; and 3) syndactylous animals possessing the sy gene from other syndactylous animals were sought in the limbs from 53 syndactylous sy/sy cattle, two normal overlap sy/sy bulls, and six normal +/sy cattle, all U.S. Holsteins. All but two syndactylous cattle had osteologic anomalies of the manus or pes which paralleled the asymmetrical patterns of external syndactylism, including right-left and front-rear gradients. The exceptions had only partial nondivision of the coronary borders of their right front hooves. Synostoses of the intermediate and ulnar carpal bones, the only anomalies of the normal overlap animals, occurred on normal and syndactylous limbs, as did synostoses of the first tarsal bone with the fused second and third tarsal and, occasionally, of the ulnar, intermediate, and radial carpals. The right metacarpal was brachydactylous in most animals; in some, the distal trochleas were reduced to a single trochlea with two saggital ridges and occasionally with only one saggital ridge. The distal perforating canal disappeared, followed by the proximal. Some animals had a polydactylous enlargement of the accessory metacarpals. The sesamoid count was variably reduced. The second phalanges most frequently were horizontally synostotic, followed by the third and first, respectively. Normal heterozygous animals had no osteologic anomalies. © 1969, American Dairy Science Association. All rights reserved.