Breeding Ewe Lambs: An Australasian Perspective

SIMPLE SUMMARY: There are a number of potential advantages and disadvantages associated with breeding ewe lambs at 7 to 9 months of age. In extensive pastoral systems, such as those in Australia and New Zealand, a relatively low percentage of ewe lambs are bred, which suggests that the decision to breed ewe lambs is based on the perception that the potential advantages outweigh the disadvantages. This review outlines current knowledge of ewe lamb breeding with a focus on more recent Australasian studies, particularly relating to factors that influence breeding success. Differences in reproductive success of ewe lambs and mature ewes are highlighted to help identify where differences occur. Furthermore, management guidelines beginning from the weaning of the young ewe herself, through her first breeding, post-weaning of her first set of lambs, and to her second breeding are outlined. Of particular importance is ensuring that ewe lamb live weight and/or body condition score targets at breeding at 7 to 9 months of age are met and appropriate feeding guidelines are followed throughout pregnancy. Adherence to these guidelines should ensure that reproductive success is high and that the potential disadvantages of breeding ewe lambs are mitigated. The potential long-term effects of breeding ewe lambs are also outlined. The review highlights where knowledge is lacking, with a particular focus on Australasian production systems, and where further research is required. ABSTRACT: A number of potential advantages have been identified for breeding ewe lambs at 7 to 9 months of age, including increased lifetime productivity and profitability. However, breeding at this young age in extensive pastoral systems, such as in Australasia, can be associated with a number of disadvantages resulting in uptake of this management procedure being relatively low. This review highlights the known differences between ewe lamb and mature ewe reproductive performance, thus differing in their management. The review then summaries the scientific literature of factors that affect ewe lamb reproductive success, with a focus on recent studies conducted under extensive pasture-based conditions in Australasia. In particular, this review outlines the importance of ewe lamb live weight and body condition score on their productivity. The potential long-term consequences of breeding a ewe lamb at a young age in terms of her future success and that of her offspring to weaning are briefly outlined. In addition, the potential impacts of selecting progeny born to ewe lambs as future replacement ewes are discussed. Throughout this review, optimal management guidelines from prior to breeding the ewe lambs until rebreeding at 2 years of age are provided. Lastly, areas requiring future research are identified and discussed.