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A polled bull or cow is one that is born without horn and does not grow horns. Cattle descend from wild breeds where both bulls and cows grow large horns, and most domestic breeds retain this trait.
Cattle with horns can be dangerous to other cattle and to people. For this reason most calves are dehorned at a young age, before the horn bud attaches to the skull and begins to develop into a full horn.
The advantage of polled genetics is that you do not need to dehorn the cattle, a labor-intensive and potentially painful procedure.
The polled gene is dominant, so if either parent is carrying this gene the calf will be born polled (and not develop horns)
Polled genetics are available in many cattle breeds including: Aberdeen-Angus, Ayrshire, Belted Galloway, British White, Charolais, Dexter, Durham and Hereford. The proportion of polled animals varies by breed and location with polled, horned and mixed herds.
The picture (right) shows Welsh Black cattle where some of the animals are horned and others polled, demonstrated mixed genetics in the herd.
The polled gene is dominant, so a herd can be moved from horned to polled over several generations by using a polled bull. However in many breeds, polled bulls with desirable production qualities are not avialable.
Polled lines of Herefords were first developed in the 1889. Warren Gammon in Des Moines is considered the originator of the breed. He got the idea from seeing other lines of polled cattle at the Trans Mississippi World Fair.
Red Polled Cattle
One breed synonymous with polled genetics is the Red Poll. The first herd book for this breed dated from 1882. This heritage breed is raised for both meat and milk.
Many modern herds have not taken the time to select for polledness and so continue to carry out painful disbudding to prevent their calves from developing horns.
* Goonewardene, L. A., M. A. Price, E. Okine, and R. T. Berg. "Behavioral responses to handling and restraint in dehorned and polled cattle." Applied Animal Behaviour Science 64, no. 3 (1999): 159-167.
Some people suggest there are negative temperament traits associated with polled genes but research has not found this to be the case.*
A 'smooth polled' or 'double polled' cow or steer is one that is homozygous for the polled gene, and so if breed with another smooth polled animal none of their offspring will ever have horns.
However a completely different gene may cause a calf to develop very small and malformed horns called scurs. The scurs can sometimes be quite large but they are not attached to the animals skull and so do not serve as effective weapons
Scurred cattle are technically considered polled, but most breeders want to develop cattle with no horn development at all and so select against scurs.
Polled breeds also occur in other species, such as sheep and goats.