Age of eruption of the first permanent incisors varies between Merino genotypes and is related to liveweight

•Average age of incisor eruption varied by up to 2.5 months between sire groups.•Eruption was completed over 3 months for some sires but over 6 months for others.•Eruption occurred earlier for animals that were heavier at 12 months of age.•Age at eruption was influenced more by weaning weight than growth rate post weaning.•Knowing the pattern of eruption for a specific genotype can help optimise the sale value.