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Some Developments in Overshot and Undershot Jaw Studies in Sheep

Idaho Experiment Station

Abstract

It appears from the somewhat limited literature that is available on the subject of overshot and undershot jaws in sheep that there is not a uniform understanding with respect to what these two terms signify. It occurs to the author that the term "overshot" describes reasonably well a condition in which the lower jaw is so short that the upper jaw, though it may be normal, extends over the lower jaw so far that the incisors will register at varying points back of the anterior angle of the pad, instead of immediately at this point. The term "undershot" would then refer to a condition in which the upper jaw is so short that the incisors extend beyond the dental pad.

The results published on defective jaw studies in sheep have not been uniformly interpreted by judges of sheep nor by practical sheepmen. A few judges, and a larger number of practical sheepmen, have become sheep "mouth-conscious" and have rejected any individual, regardless of age, that showed even a slight tendency to be defective. On the other hand, some sheepmen do not consider the problem serious enough to reject even those that have very defective jaws. Studies so far indicate that both these extreme points of view are not in accord with the available data; that caution should be applied in passing judgment, especially on the smaller variations; and that the more pronounced cases are definitely inherited.