In years to come, Little Country Acres will be able to offer quality polled rams to shepherds who, for one reason or another, make the personal decision to not keep or manage horned rams.
It should be noted that the North American Shetland Sheep Association (NASSA), does not discriminate against scurred or polled rams. Nor does the Breed Standard disqualify either one of them. Polled and scurred rams are perfectly acceptable, as are horned, scurred, and polled ewes.
All information on Horn terminology, phenotypes, and horn classification was obtained from the book "Breeding Merinos" by C.H.S. Dolling. This book is out of print. Additional information from the "Mendalian Inheritance in Sheep 1996" research article along with other sources.
Dolling's horn theory is based on a triple allele series, with one locus (HO). They are listed here, in order of dominance.
P is polled. It is incompletely dominant in rams, almost completely dominant in ewes. Examples: most commercial sheep; Cheviots, Hampshires, Suffolk, Oxfords are PP.
p' is horns in both sexes, also called the "horned ewe allele". Both rams and ewes exhibit substantial horn growth. Examples: Scottish Blackface, Jacobs, Icelandics would be p'p'.
p is horned. In some sheep breeds, including the shetland, this gene is "sex-influenced". Rams typically have large horns, and in ewes, p can express as anything from no obvious horn growth, through barely visible bone knobs. A careful manual examination of the horn site on the hornless ewe may reveal small bone knobs that do not break the surface of the skin. These sheep would be genotyped as pp.
Most shetland ewes carry two horn genes. These ewes would be described as "hornless". They are not considered polled if they are not carrying a poll (P) gene. They are not "horned", as they have no obvious horns. So "hornless" is an appropriate description. It is probable that most pp shetland ewes have horn buds that are so small, they do not break the skin surface. Some can be felt, but some are so small they cannot.
As with color genetics, each sheep passes down one of their two alleles to each lamb, for a total of two inherited genes. So a sheep can be PP (full polled), Pp (half polled), pp (horned or "hornless"), or p'p' (horned in both sexes).
There may or may not be other loci affecting horns and scurs. A variety in horn and scur length, width of horn base, degree of skull depression, and growth rate have been observed in half-poll Shetland rams, in both juvenile and mature animals.
Horn genetics study is a work in progress. These pages will be updated as new information is obtained regarding sheep horn genetics.
A method of grading our sheep.
