[Jacob-list] Reply on Jacob sheep questions

[Neal and Louise Grose]

Barbara Peters has asked some very good questions in her jacoblist posting on 10/8. The answers are more complicated than you might think, and I am going to provide only a basic outline as I see things.

"Another is how fragile are four horned horns?
> We used to have Scottish blackface sheep and we could use their horns for
> handles when moving them about.  Can you do the same with four horned sheep?"
Answer: I have several types of fencing. I have less problems with NZ style multiple stranded electric fence than any other. Sheep lead with their nose for the most part, so a good jolt is usually enough to get the adults in line. However, the leading cause of death in sheep is still Terminal Ovine Stupidity Syndrome.
 Jacob sheep horns SHOULD BE at least as strong as Scottish Blackface horns. This varies, and there is some debate going on as to what the minimum horn strength should be, especially in the ewes. An underlying problem is that the total horn mass is not significantly different between 2 and 4 horned animals. [My observation is that a 4 horned ram may have about 150% of the horn mass that his 2 horned brother would have.] Having horns strong enough to use as handles is a pretty good rule of thumb for the ewes. Some lines of sheep are having problems with diminutive horns in the ewes, and this is undesirable. The rub is that horn genetics in sheep are more complicated than in cattle. We have to deal with both dominant and recessive polled, hornless (not polled), sex-linked... many of these traits are recessive and can be submerged in the purebred population without coming to the forefront. [Some see this as evidence of crossbreeding, but I think that is a hard case to make.] More importantly, horn strength is directly proportional to bone mass. Jacob sheep are supposed to be a flat boned [sometimes referred to as fine boned] breed. Efforts to breed for big horns will result in animals that are large and coarse boned. Conversely, there is a chance that breeding for small animals and fine fleece can inadvertently result in eliminating horns, especially in the ewes.
Sheep fight smart, or more specifically, they have mechanisms to avoid fights. Sheep are genetically dispositioned to show deference to the guy with the biggest set of whoppers..er horns. Therefore, a large 2 horned ram will often defer to a smaller 4 horned ram unless aggravated. 2- horned rams actually hit with the thick pad on the back of their skull, not the top of the skull. 4-horned rams do not have this option, and will adopt a circle/side swipe at the rib approach if they are smart.[otherwise, see T.O.S.S. above.] 


"Next questions are related to color.  Some people have written that Jacob
> come in black and white, brown and white, and lilac and white.  Other people
> only mention lilac/white and black/white.  Are there really the three
> colors, or are the brown one just faded blacks?"

Answer [such as it is]: Color in Jacob sheep is extremely complicated. They are white dominate/black dominate/piebald. The piebald gene is recessive in some bloodlines and dominate in others. There are variations in the piebald characteristics, such as numerous small black markings versus large black patches. [Technically, the white is the "spot". As in Holstein cattle, true Jacob spotting is black with white extremities.] Color in inbred populations tends to be somewhat cleaner [less freckling/ticking] than in outcrossed animals. Lilac is "whatever is not black" in common usage. Lilac is NOT faded black.
    Now, when you figure out the genetics of lilac, let the rest of us know. Lilac color varies, with descriptions ranging from 'chocolate' to 'pewter/tan'. Within the 'purebred' population of Jacobs, lilac acts like a simple recessive to the black. Bx is black and white, and bb is lilac and white..lilac expressed only as homozygous recessive. The problem is when lilac Jacob sheep are test crossed. Test crosses allow one gene to examined at a time. In some cases, when lilac Jacob is test crossed onto homozygous white dominate sheep, such as Corriedale, the cross produces black or black piebald lambs. This shouldn't happen. If lilac is a simple recessive, then by definition, black is not "present" and the cross should produce either white or lilac lambs, depending on the dominance of the lilac. Instead, in this case the black comes through from the lilac parent. Additional test crossing is being done by several people to test cross lilac Jacob onto moorit colored sheep. Since moorit is the most recessive color, this should tell us more. There are some reports that there is considerable variation in the color of lilacXmoorit lambs, [some black and some brown] indicating that there are probably several 'lilac' genes, with different modes of action.

OK, this was more than you wanted to know.

Neal Grose
North Carolina








-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.pairlist.net/pipermail/jacob-list/attachments/20021008/2c05e70a/attachment.htm