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

Abstract

The age at which the four pairs of permanent incisors emerged, and the interval between first emergence and the attainment of full size, was recorded from observations taken every 2 weeks on 332 female cattle of a herd comprising the Ayrshire, Friesian and Jersey breeds, and the reciprocal crosses among them.The 1st pair of incisors emerged at a mean age of 101 weeks of age and later pairs at approximately 30-week intervals, with the s.d. increasing proportionately from 7 to 14 weeks. Full size of the incisors was attained, on average, 4-0, 2-4, 3-0 and 5-6 weeks after the initial observations on incisor pairs 1 to 4 respectively. Breed (or cross) and season of birth significantly affected the age at emergence of the 1st and 2nd pairs of teeth, and breed also affected the age for the 4th pair. Relative to the Friesian breed, an Ayrshire parent delayed emergence of both 1st and 2nd incisor pairs by approximately 4 weeks, and a Jersey parent delayed emergence of all four pairs. The maternal effect was opposite in sign to the effect of breed substitution; in particular, a Jersey dam caused a reduction in the age at emergence. There was no evidence of heterosis in the crosses. On average, each pair of incisors erupted approximately 4 weeks earlier for cows born between October and December than for those born in the period April to June.Age at calving, lactation length, milk yield, body weights and the ratio of 18-month body weight to that at 42 months (as an estimate of proportion of maturity) were not significantly correlated with the dental traits. Correlations between age at emergence of adjacent incisor pairs were approximately 0-7, a value higher than that between pairs separated by longer time intervals.

The anterior tooth development of cattle presented for slaughter: an analysis of age, sex and breed

“…The orderly sequence of development is illustrated in Figure 2 as is the relatively short time that the intermediate stages (1, 3, 5, 7) are present before emergence of the second of the respective pairs thus accounting for the low numbers of intermediates recorded. There is considerable overlap of age at which each stage is presented and an increase in the age range as successive pairs develop, which is in agreement with previous authors (Andrews, 1975;Weiner and Forster, 1982). The age range from emergence of the first pair to full development of the fourth pair (also known as a full mouth) is shown as 500 to 1800 days, which is also consistent with previous studies (Andrews, 1974;Andrews, 1975;Brooks and Hodges, 1979;Graham and Price, 1982).…”

“…Although the recording system did not differentiate between stages of emergence, this narrow timeframe in which the intermediates are present does provide a point for comparison. The peak incidence for first and third teeth can be seen in Figure 2 as ,700 days (23 months) and 915 days (30 months), respectively, which suggests that emergence of the corresponding pair is occurring at similar ages to that found by Brooks and Hodges (1979) and Weiner and Forster (1982), and later than that found by Andrews (1975). The peaks for the fifth and seventh teeth are more difficult to interpret given the relatively small numbers and much wider range.…”

“…The nature and purpose of the current study required that the cross-sectional method was used, whereby each animal is examined on only one occasion. The longitudinal method, which involves examining the same group or groups of animals on a regular basis over a period of time, has also been used (Brooks and Hodges, 1979;Weiner and Forster, 1982). However, a study by Andrews (1974) comparing both methods in Friesian cattle found no statistical difference in the relationship between age and anterior tooth development when using either method.…”

“…The period between the first and second of a pair emerging has been cited as ,2 to 3 weeks (Brooks and Hodges, 1979) and the period from first emergence from the gum to full tooth development up to 6 weeks (Weiner and Forster, 1982) so that generally the second of the pair will be present by the time the corresponding intermediate is half up. Although the recording system did not differentiate between stages of emergence, this narrow timeframe in which the intermediates are present does provide a point for comparison.…”

“…Thus, the approach adopted by previous studies to investigate the relationship between dentition stage and age, assuming a random sample from a 'natural' population, could not be adopted here. Previous studies have reported mean ages and ranges for each dentition stage (Andrews, 1975;Brooks and Hodges, 1979;Weiner and Forster, 1982). In the present study, the relationship between dentition stage and age was investigated using an ordered category response model as implemented within the statistics program MLwiN 2.24 (Rasbash et al, 2010).…”