579. A study of variation in twin cattle: IV. Emergence of permanent incisor teeth

Abstract

1. Data are presented on variation in age at eruption of permanent incisor teeth in one-egg (MZ) and two-egg (DZ) twins and in pairs of half sisters (HZ). The 1st pair of incisors erupted when animals were on average 100 weeks old and the other three pairs came at roughly 26-week intervals thereafter. Variation in age at eruption increased from 1st to 4th incisors, but the coefficient of variation remained constant at about 8%. The mean interval between eruption and complete emergence was about 5 weeks for the first three pairs of teeth and nearly 10 weeks for the 4th pair.2. Variation in age at eruption within MZ pairs was no greater than that between left and right sides of the same animal. DZ displayed greater within-pair variances than MZ twins, and HZ pairs greater than DZ.3. Correlations of age at eruption of teeth with body weight and with gain in weight were negative but non-significant. Age at eruption of 1st and of 3rd teeth was positively correlated with age at 1st and 2nd calving, but eruption of 2nd and of 4th teeth was not.4. For 2nd, 3rd and 4th incisors, the intra-pair variance of the HZ group was in excess of that expected. This can be interpreted to mean that the estimates of environmental and genetic variation derivable from MZ and DZ pairs are not adequate to account for all the variation within HZ pairs.

Studies of the permanent incisor eruption, and body development, of the Large East African Zebu (Boran): 2. Relations of incisor eruption with body growth, body development, and carcass composition

“…From the tests for linearity it appears that within animals the period around 126 weeks is a period of a major change in growth rate, perhaps suggesting that at this stage or shortly after fattening begins. The finding that the early eruptors are larger at all the stages of growth is consistent with the trends detected by Wiener & Donald (1955) and Gam et al (19656) from their estimations of the correlations between eruption age and body weight at fixed age, which were all negative, although non-significant. With the difference of the order of 4 % this could be of practical importance.…”

“…It appears that there have been only two other reports of an examination of the association of eruption and growth rate, in which the analytical technique did not involve a confounding effect of age (Wiener & Donald, 1955;Simpson & Wilson, 1971); neither of these was able to detect any significant relations, although the first observed a trend for animals that completed the eruption process quicker, from the first to the fourth pair, to have a greater growth rate over the corresponding period of time. These authors correlated estimates of total growth rate with different measures of tooth development, but it would appear likely that neither was sufnciently sensitive to detect the differences of the order observed in the present data.…”

“…These authors correlated estimates of total growth rate with different measures of tooth development, but it would appear likely that neither was sufnciently sensitive to detect the differences of the order observed in the present data. Also the data of Wiener & Donald (1955) would have contained additional variation because the animals were breeding females.…”

“…B. CABLES AND K. MEIDIE LAMPKIN been extremely few. The main one with ruminants has been that of Wiener & Donald (1955) who obtained non-significant correlations between eruption age of the first incisor pair and body weight at a fixed comparable age (18 months); and between the time taken between the eruption of the first and fourth incisor pairs, and body weight gain over the comparable period (18-42 months).…”

Variation in the age at emergence of incisor teeth in cattle of different breeds

“…ALTHOUGH THE emergence of teeth has traditionally been used to determine age in cattle, a number of factors including breed, season of birth, nutrition and sex have been shown to contribute to the considerable variability in age at emergence of the incisors found in practice (Wiener and Donald, 1955;Andrews, 1976;Andrews and Wedderburn, 1977;Brookes and Hodges, 1979). The present study is concerned primarily with the influence of breed and of crossbreeding, of Ayrshires, Friesians and Jerseys, on the age of emergence, and on the interval between the start and the full emergence, of the permanent incisors.…”