Attrition of the Hypsodont (Sheep's) Tooth 



C. R. BARNICOAT, Cawthron Institute, Nelson, New Zealand 



EXCESSIVE wear of incisor teeth of sheep is an economic problem 

 in New Zealand which has become aggravated during the past thirty 

 to forty years. Teeth wear much more rapidly on improved pasture, 

 chiefly rye grass (Lolium perenne) and white clover (Trifolium 

 re pens), than on the fine native grasses of low carrving capacitv. 

 Excessive wear of sheep's teeth is now becoming a problem in other 

 countries where extensive methods of farming are being replaced 

 by intensive practices through the introduction of improved pastures. 

 Most of the results reported in this paper were obtained with Rom- 

 ney sheep, the predominant breed in New Zealand. 



Since the problem is of regional occurrence — certain districts be- 

 ing noted for sheep "not holding their mouths" — first impressions 

 were that it was of nutritional origin, related to soils and pasture 

 composition and possibh^ to defective mineral metabolism. It was 

 eventually concluded that the cause is not nutritional in the gen- 

 erally accepted sense, however, since the defect is quite difi^erent 

 from caries; and there were no skeletal abnormalities, which are 

 usually associated with deranged calcification. The wear is also dis- 

 tinct from abrasion caused by the presence of foreign gritty particles 

 in the food. The various factors concerned compare and contrast 

 interestingly with those responsible for dental caries in man ( Barni- 

 coat, 1957). 



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