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Thoughts on Horn Genetics

Please note: This article was originally tid-bits from my column, Michigan Shepherding, in the Black Sheep Newsletter, Number 105. Please contact BSN for back copies of the originals and stay tuned for more tid-bits in upcoming issues of BSN. Reprinted in the North American Shetland Sheepbreeders Association News, April 2001, page 5.

A breeder recently said: "I need a little help on some basic genetics. How strong is the tendency for a ram to pass on his particular type of horns? Does the horn type of the dam's sire ever come through? What about succeeding generations? If the progeny of a ram with tight horns is mated to a ram with wide-set horns, what will the result be between the two types? What factors do you cull for? What do you breed for?" These are good questions though not easily answered.

My extensive research into horns indicates that the tendency for a ram to pass on his horn type is very strong-this means horn spread from tip to tip, coil shape versus spiral shape, cross-sectional shape, triangular shape versus round, color, striping, etc. But the often hidden horn type carried by the dam definitely enters into the results too, since many of the ewes are hornless themselves, but come from a "horned" line. Environment and nutrition offer significant contributing factors to horn growth.

For the sake of preserving other desirable traits, we might have to use a ram with less than perfect horns. This may be all right if we are careful in our selection of retainable offspring and not afraid to sacrifice undesirables that might result. But in my opinion, an undesirable horn (i.e., unsafe or bad horn) perpetuates undesirable horns. I recently had a call from a many how had a young ram with a horn that was about to grow into his neck. He wanted to know what I would do. I told him I would both castrate and trim the horn, or eat him. His reply was, "But he's such a pretty ram." Not in my book, there are too many really nice horned rams out there, why even consider one with bad horns?

It's difficult dealing with problem horns, I know. I've done it for twenty years and have learned that the only way not to have this problem is by not perpetuating it. If you are sure that all the animals in the last several generations have good horns (ewe lines as well as ram lines), you can be pretty darned sure that your resulting ram lambs, and the ram lambs from the resulting ewe lambs, will have good horns. I know it's hard for many people to think in this direction, but maybe it's time to start.

Some breeders say, well you can still get a finger or two between the horn and cheek. You need to remember that horn will increase in diameter as the animal gets older, so that horn can quickly become too tight. Also watch how he chews-it's sideways, not up and down, sideways! About the time he starts hitting his jaws on the horn, first his bite will be affected, then his feed efficiency. It breaks my heart every time I see a ram with bad horns or a ram lamb headed that way.

To me, horn shape doesn't matter, cross-sectioned triangular or round, a coiled horn or a spiral horn; any of these are fine, as long as they curl away from the head or at least parallel to it. I want to see a lot of daylight between the head, cheeks, and the horn. Digging maggots out from heads with tight fitting horns or ulcerated cheeks is not fun. While I don't care for the "tea-cup" type of horn, I do have a young ram with this type. I'm waiting for his first lambs to hit the ground--his genes are important because he is from a closed flock we found in Massachusetts.

Another person asked "I always assumed that any sheep gets an average fifty percent of the ewe's genes for horns and fifty percent of the ram's, realizing it could go more either way. Then I suppose there is the question of what exactly genetically governs horns; i.e., is a locus "on" or "off" for wide horns or is it a mix of close and far. What conclusions did you come to, especially regarding breeding ewes with close horns to rams with wide horns; i.e., what would you generally expect in the offspring?"

Okay, "What exactly genetically governs horns?" More than you can imagine, unfortunately. In some individuals, horned genes are truly "sex-linked." This means rams are horned, ewes are polled; in others, rams are horned, but ewes can be scurred, or even horned; rams can also be scurred or polled. This makes for a big genetic mess, compounded by the fact that "polledness" is the dominant characteristic, while "horned" is a recessive trait. I don't even pretend to know or understand it all.

"What conclusions did you come to, especially regarding breeding ewes with close horn (genetics), to rams with wide horns; i.e., what would you generally expect in the offspring?" I guess I would have to answer that you could expect a certain percentage of wide horns, a certain percentage of close horns, plus everything in between. The ram lambs would show the resulting horn genetics, while the ewe lambs would carry it. So, if you only retain the rams with the wide horns, then you've got a good start and the beginning of a "breeding plan" or goal. Make sense?

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