Abstract
Suboptimal reproductive performance of maiden ewes impacts sheep enterprise productivity, but the extent and causes of the poorer reproductive performance of maiden ewes on Australian sheep farms are not well understood. Here we show the reproductive performance of maiden ewes relative to their multiparous counterparts on the same farms across Australia using a cohort survey. Data were collated for 79 farms (413,702 ewes) across major sheep producing regions in Australia. There was a 58% difference in marking rate for non-Merino maiden ewe lambs compared to multiparous ewes, and this was attributable to 50% difference in reproductive rate and 16% difference in lamb survival. For maiden Merino hogget ewes, there was a 22% difference in marking rate compared to mature multiparous ewes and this was attributable to 24% difference in reproductive rate and 3% difference for lamb survival. Reproductive performance (reproductive rate, lamb survival and marking rate) in maiden Merino hoggets was correlated with that for mature ewes on the same farm, but these correlations were weak or nonexistent for ewe lambs. Our findings show that veterinarians can add value to sheep enterprises by working with managers to assess reproductive rate and lamb survival in different ewe cohorts and compare current performance against industry benchmarks. This will inform interventions targeted to ewe age groups and stages of reproductive cycle with greatest opportunity to deliver improvement in farm profitability and animal welfare.