Polled livestock

Polled livestock are livestock without horns in species which are normally horned. The term refers to both breeds and strains that are naturally polled through selective breeding and also to naturally horned animals that have been disbudded. Natural polling occurs in cattle, yaks, water buffalo, and goats, and in these animals it affects both sexes equally; in sheep, by contrast, both sexes may be horned, both polled, or only the females polled. The history of breeding polled livestock starts about 6000 years BC. The archaic term or is sometimes used to refer to hornless livestock (especially cattle) in folk songs, folk 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. In cattle, the polled allele is genetically dominant to that for horns. The polled trait is far more common in beef breeds than in dairy breeds. CRISPR technology is being developed to create polled versions of dairy breeds. In sheep, the allele for horns in both sexes is partially dominant to the allele for being polled in both sexes, and both of these are dominant to that for polling in the female only. The development of true breeding polled goats is discouraged as the polled locus is strongly associated with Polled Intersex Syndrome (PIS). Naturally polled water buffalo also have genital defects. Naturally polled animals may have scurs – small, loose, horny growths in the skin where their horns would be. In cattle, this trait has been traced to a separate gene (on a different chromosome) from that responsible for polling. However, the presence of the allele for scurs in cattle can only be seen in a polled animal, because horns replace the scurs in horned animals. Similar scurs may also occur where disbudding of a naturally horned animal has been incomplete. Polled livestock are preferred by many farmers for a variety of reasons, the foremost being that horns can pose a physical danger to humans, other livestock and equipment.