Wear of sheep’s teeth

Abstract

A survey of wear of sheep’s teeth in the Wairarapa district led to detailed investigations of three farms on which sheep showed high, medium, and low rates of wear of incisor teeth. Dental examination of five-year-old ewes showed that mean lengths of incisor teeth were 0.15, 0.35, and 0.55 in. on high-, medium-, and low-wear farms respectively. Breed differences, or malocclusion of jaws, did not appear to be involved. A concurrent paper (Part II—in this issue) suggests that chemical differences in spring pastures are not responsible for the wear differences. Analysis of faeces collected at monthly intervals over 1964–65 showed that their contents of soil were highest on the high-wear farm, lowest on the low-wear farm, and intermediate on the medium-wear farm. Soil was ingested in greatest amounts over the wet cold months when pastures are short and grazing pressure high. Calculated values for ingested soil July-October are probably about 25 lb, 10 lb, and 1 lb for each animal on high-, medium-, and low-wear farms respectively. Soil material separated from faeces was shown to be highly abrasive. It seems unlikely that plant phytoliths play an important role. It is proposed that ingested soil is the main agent involved and that the degree of wear is directly related to the quantity of soil taken in by the grazing animal.