Mundi: Yes that is a coincidence because Farsaell, Partur, Snaer, and the other guys are very big rams. The head broadness can vary very much between rams.
Gary: Horned Icelandics have generally thicker eyemuscling then polled Icelandics. Other than deliberate genetic selection for thicker muscling, is it also due to the extra weight of the horns, or a generally larger and broader head?
Mundi: I don't think so. The horns are not that heavy that they will affect. It's genetics. The size and broadness of the head is more linked to other qualities. We should turn this around and say bigger and meatier animals with better conformations have bigger and wider heads.
Gary: Talking about head broadness, there is a fad here in North America at the moment having to do with measuring the distance between the eyebrows of newly born ramlambs and deliberately selecting those with narrower heads. If bigger and meatier animals with better conformations tend to have bigger and wider heads, could this selection for narrower heads to ease birthing problems have any merit, or possibly be harmful or counterproductive?
Mundi: I have never given this serious though, but be very careful about this. Selecting for a narrower head could be selection for a narrow bone structure. That means worse conformation, inferior meat qualities, etc. I understand that people are concerned about birth problems, but here in Iceland we find it more related to exercise and feeding during pregnancy. Exercise for pregnant ewes is good, just as for women, and overfeeding causes greater birth weight with the possibility of birth difficulties. Here we find big horns the biggest problem concerning birth difficulties. Another thing you should all bear in mind is that a narrow and low rump usually means a narrow pelvis and therefore a narrow birth canal. That is what really gives us birth problems. i fear that narrow head breeding could be narrow pelvis breeding.
Gary: if meatier heterozygous-polled rams with better conformations and larger heads were crossed with unimproved or somewhat improved horned ewes, could a greater percentage of difficult births result due to big heads with horns?
Mundi: I don't think that will affect. As I said, it's more the size of the lambs around the breast and hips that could give problems in polled sheep as well as the birth canal width.
Gary: Does heavier rump and leg muscling like on the ewes at Stora Armott affect the ease of birthing in any way?
Mundi: It doesn't look that way. Lambing difficulties are most often because of too much feeding during late pregnancy, the lambs are too big and heavy. Sometimes very big and coarse horns give problems as well as not enough exercise for the ewes during pregnancy. That's why many farmers here use polled rams on the hoggets (or the lambs bred in autumn) and try to let them out of the barn during the day if weather conditions are OK.
Gary: Does breeding for stockier, broader sheep (meat conformation vs. unimproved or Leader) yield wider hips and larger birth canal?
Mundi: Not necessarily. Often the high hips give more flexibility to the birth canal making it act wider, though it might look the other way. The size and shape of the birth canal, is not necessarily linked to breeding for meat qualities. This is why for instance in dairy breeding we have indexes for calfing, etc. We could select for wider hips, but doing so can also make the hips or the rump lower, decreasing the flexibility in the birth canal during lambing. That can also make problems.
Gary: As time passes and the sheep get more heavily muscled and lower to the ground, does the bone structure as a whole get thicker and more suited to the animals extra strength? Or do they remain light-boned like most of the unimproved animals. (the canon bone for example, does it not only shorten, but thicken somewhat too?)
Mundi: A difficult question to answer. Breeding for meat qualities certainly means changing the meat/bone ratio of the animal. Looking at the canon bone for instance, it appears to be the way you described, it gets thicker when it's shortened, but I'm not sure that it is in the same ratio. Here in Iceland we have stopped breeding for a shorter canon bone because it means smaller sheep. We emphasize now on increasing the meat and meat quality as well as breeding for heavy milkers which gives a good growth rate in the lambs. And then it's the prolificacy that we mustn't forget, having two lambs per ewe is the optimal bearing in mind that each ewe has two teats.
Gary: Doesn't extensive crossing of horned to polled usually ruin horning?
Mundi: It depends on the selection of breeding animals, but usually yes.
