Dental occlusion in young bulls of different breeds

SUMMARY The position of the incisor teeth in relation to the maxillary pad was examined in bulls (at approximately 10 months old). Visual gradings grouped into five classes were made on 5582 bulls of eight breeds in the course of inspection for licensing. In addition, measurements of the tooth positions (grouped into 11 classes) were made on separate samples of 1163 Galloway and 191 Ayrshire bulls. Among the beef breeds 84·0% of all tooth positions were classed as being normal and 96·6% of those among the dairy breeds. The proportion of mouths with incisor teeth forward of the maxillary pad was higher among the beef breeds. Individual breeds within the beef and dairy types also differed significantly. Herds of the Galloway and of the Ayrshire breeds, judged on the bulls submitted for licensing, differed in the distributions of the position at which the incisor teeth met the pad. Herds also differed when judged on the occlusion of the sons of their bulls. Heritability was calculated for Galloways by half-sib correlation and sire-son regression, yielding estimates from 0·31 to 1·28, suggesting that at least some of the variation is inherited. The undershot and overshot conditions were found together only rarely among the male offspring of any one bull.