ATTRITION OF THE IIYPSODONT TOOTH 161 



tal structure, as well as irregularities and gaps in the molars. Mc- 

 Roberts and Hill (1962) concluded that "diet deficient in calcium 

 had a greater effect on the teeth than on the skeleton, while the 

 diet deficient in phosphorus and in Vitamin D had a greater effect 

 on the skeleton than on the teeth." 



Recommended minimum adequate requirements of calcium and 

 phosphorus for sheep (Natl. Research Council Natl. Acad. Sci. 

 (U. S.), 1949) as percentage of dry matter are: 



Ca P Ca/P 



Growing lambs 0.18 0.15 1.2 



Ewes 0.20-0.23 0.18-0.24 1.2-1.6 



The average composition of herbage eaten by New Zealand sheep 

 in relation to extent of wear of teeth is recorded in Table I. The in- 

 take of calcium and phosphorus is satisfactory by accepted stand- 

 ards; and, in fact, the better teeth are found in animals ingesting 

 herbage with the lower mineral content. 



No relationships between quality of sheep's teeth and deficiencies 

 or imbalances of microelements (i.e. the biologically important cop- 

 per, molybdenum, cobalt, iron, fluorine, iodine* ) were established; 

 nor is there any apparent relationship with geological formation or 

 soil type. There is no evidence to support the theory that vitamin 

 A (as the provitamin carotene) or D is implicated, and the water- 

 soluble vitamins are believed to be more than amply provided by 

 the rumen microflora (Barnicoat, 1959). 



Analyses of enamels and dentines of teeth of New Zealand sheep 

 are recorded in Table II. Their stoichiometric relationships are given 

 in Table III. Figures vary little, and are not influenced by the 

 quality of the mouth. These analytical results are similar to those 

 reported by numerous workers for human teeth (Leicester, 1949). 



Spectrographic analyses of enamel and dentine for 19 microele- 

 ments of biological importance, including aluminium, cobalt, copper, 

 iron, molybdenum, silicon, vanadium, and zinc, showed no differ- 



* Paradontal disease, chiefly affecting molars, is associated with selenium de- 

 ficiency (Hartley and Grant, 1961 ). 



