Polled livestock are livestock without horns in species which are normally horned. The term refers to both and strains that are naturally polled through selective breeding and also to naturally horned animals that have been disbudded.
Terminology
The
Archaism term or
is sometimes used to refer to hornless livestock (especially cattle) in
Folk music,
Folklore, and
poetry,
and in the name of the polled
Irish Moiled cattle breed. "Muley" derives from
Irish language and
Scottish Gaelic maol, and
Welsh language moel.
Genetics
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.[ Soay Sheep: Dynamics and Selection in an Island Population, T H Clutton-Brock and J M Pemberton (eds), Cambridge University Press (2004), : Appendix 2 (quoted in Horn Phenotypes and Genotypes in Soay Sheep, Saltmarsh Ranch Soay Sheep).]
The development of true breeding polled is discouraged as the polled locus is strongly associated with Polled Intersex Syndrome (PIS).
Naturally polled water buffalo also have genital defects.[Caldwell, HS (Editor), 1977. The Water Buffalo. Animal Production and Health Series 4. Food and Agriculture Organization, Rome. (quoted in Charles G. Hickman, Cattle genetic resources, 1991, p 246, Elsevier Health Sciences )]
Scurs
Naturally polled animals may have
– 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.
Reasons for polling
Polled livestock are preferred by many
for a variety of reasons, the foremost being that horns can pose a physical danger to humans, other livestock and equipment. Horns may also interfere with equipment used with livestock (such as a
cattle crush), or they may become damaged during handling.
In other circumstances, horned animals may be preferred, for example, to help the animal defend itself against , to allow the attachment of head to draught oxen, to provide a hand-hold on smaller animals such as sheep, or for aesthetic reasons – in some breeds the retention of horns is required for showing.
In the US no show requires horns to be left on. Most shows require at a minimum blunting of the horns to a minimum diameter of inch. Boer Goat Shows allow disbudded goats.
Development of polled strains
Polled strains have been developed of many cattle breeds which were originally horned. This has usually been done by crossing with naturally polled breeds, most commonly Angus and Galloway cattle. For example, polled
Jersey cattle originated in
Ohio sometime prior to 1895. Two strains were developed, the first to appear being founded by crosses of registered Jersey bulls (the standard) on common muley (hornless) cows. These were graded up by the continued use of purebred Jersey sires, selection being made of the polled offspring of each generation, the horned progeny being discarded. Thus originated what was later known as the single-standard strain. As in the case of the Polled Shorthorns and Polled Herefords, the development of the single-standard strain was soon followed by the appearance of a double-standard strain, founded by a few naturally hornless
mutant that were discovered in registered herds of horned Jersey cattle. These standards were bred among themselves or crossed with registered horned Jerseys, followed by selection for the polled head, and the strain was developed in this way.
See also
-
Livestock dehorning
-
Castration
-
Docking
-
List of cattle breeds
-
List of domestic Asian water buffalo breeds
-
List of sheep breeds
-
List of goat breeds
