Syndactyly and Polydactyly

Syndactyly or mule foot is the partial or complete fusion of the digits of one or more feet. Reported in numerous cattle breeds, it is most prevalent in Holsteins and is inherited as a simple autosomal recessive condition. The forefeet are affected most often but 1 or all 4 feet may be affected. Animals affected with syndactyly walk slowly, usually have a high-stepping gait, and may be more prone to hyperthermia.

Polydactyly is a genetic defect of cattle, sheep, pigs, and occasionally horses. In its most common form, the second digit is developed but the medial dewclaw is missing. The toes may be fused to give rise to polysyndactyly. Rarely 1 or all 4 limbs have the condition. Polydactyly in cattle appears to be polygenic with a dominant gene at one locus and a homozygous recessive at another.