Dentition can predict maturity in young Merino sheep

Context A unique population of Merino sheep recorded for a range of production and reproduction traits presented an opportunity to calculate sire variation in dentition which may indicate maturity and influence marketing and selection decisions. A change in the definition of ‘lamb’ in the Australian sheep industry warranted an investigation of the relationship between production, reproduction and dentition. Aims To assess the variation in timing of dentition changes in Merino sheep and determine whether there are associations with key production and reproduction traits. Methods A population of 2150 pedigree-recorded Merino sheep were studied to analyse the sire variation in progeny for a range of dentition changes and production and reproduction traits. Dentition phenotypes included the age animals started to lose the deciduous lamb teeth, the age when one permanent incisor was in wear and the amount of time between these two events. Production records included bodyweight, fat and muscle traits. Reproduction records from the female progeny included the outcome of pregnancy scanning after the first joining opportunity. Sire variation for the age dentition changed was analysed. The effect of progeny age at hogget categorisation on production and reproduction was analysed. Key results Progeny that were heavier, fatter and with higher muscle measurements matured earlier. Female progeny were more likely to be pregnant if classed as hoggets earlier in life. Conclusions Dentition records provided useful indicators of maturity in Merino sheep in this study and can be used to inform decisions regarding the timing of marketing options and the likelihood of success when assessing female progeny for suitability to join at ~18 months of age. Implications Merino sires can exhibit a wide range of variation with respect to the age at which their progeny will mature, as indicated by their dentition. If animals are heavier at an earlier age, they are more likely to mature earlier, which has to be considered when planning nutritional requirements for growing out young male progeny, and females could be more successful as young breeders. Dentition is a useful tool to indicate maturity in young Merino sheep.