Studies of the dentition of sheep. 1. Clinical observations from investigations into the shedding of permanent incisor teeth by hill sheep.

SUMMARY Long-term field and laboratory studies have been carried out on the development and loss of the permanent dentition of Scottish Blackface sheep on 6 hill farms in Scotland. Clinical observations confirmed that husbandry practices and farm effect are of importance in that they influence the age at which the shedding of permanent incisors first occurs. Sheep exchanged between farms took on the characteristics of the host flock for the pattern of teeth shedding. The practice of wintering sheep on turnips in situ, or loose, was again implicated as accelerating the shedding of the teeth of such animals. It was not possible to clarify the often alleged relationship between occlusal position and the shedding of teeth. Very few sheep were found which could be described as markedly undershot or overshot in the lower jaw. On one farm breeding ewes lost teeth earlier, and more of them lost teeth, than did wethers on the same farm, but at 4½ years of age both groups were severely affected. A study of the effect of the vitamin D and phosphorus intake of lambs on their subsequent dental history was inconclusive. In all experiments where excessively heavy and early shedding of incisor teeth occurred the mature teeth were mostly long but intact and apparently healthy. The factor of severe crown wear is thus not a problem in the flocks investigated.