Polled livestock

Polled livestock are livestock without horns in species which are normally horned. The term refers both to breeds or strains which are naturally polled through selective breeding and also to naturally horned animals which have been dehorned. Natural polling occurs in cattle, yaks, water buffalo and goats, and in these it affects both sexes equally; however in sheep, both sexes may be horned, both polled, or only the females polled.

Terminology

The archaic term muley or mulley is sometimes used to refer to hornless livestock (especially cattle) in folk songs, tales and poetry, and in the name of the polled Irish Moiled cattle breed. "Muley" derives from Irish and Scottish Gaelic maol, and Welsh moel.

Genetics

In cattle, the polled allele is genetically dominant to that for horns.

In sheep, the allele for horns in both sexes is partially dominant to that for being polled in both sexes, and both of these are dominant to that for polling in the female only.

The development of wholly polled strains in goats has been discouraged by a 1944 study that suggested a link between the polling gene and hermaphrodism. Unfortunately, little study on the subject has occurred since. Naturally polled water buffalo also have genital defects.