Targeted post-weaning intervention of weaners with low growth rate pre-weaning is a profitable strategy to increase the productivity of Merino sheep

Context The post-weaning period is critical for the lifetime productivity of Merino sheep, yet weaners with low weaning weights present a significant management and economic challenge for producers. Strategies to mitigate poor performance in these ‘tail-end’ animals are essential for improving overall flock efficiency. Aims This study aimed to evaluate the biological and economic merit of preferentially feeding and managing Merino weaners with a low growth rate pre-weaning to enhance their bodyweight and wool production, and to determine whether any production gains were maintained post-treatment. Methods In total, 332 Merino weaners were separated 1 week after weaning at 3 months of age into the following three groups for a 14-week period: a group of low growth pre-weaning (LOW), a group of high growth pre-weaning (HIGH), and a mixed high and low growth pre-weaning control group (CTRL). The LOW group received a supplement averaging 200 g/head.day (provided three times per week) and fortnightly anthelmintic treatments. The HIGH and CTRL groups were managed under industry best practice. Bodyweight, growth rates, and wool characteristics were measured. Key results The LOW group exhibited significantly higher growth rates (70.5 ± 2.0 g/day; P < 0.0001) during the treatment period (Period 1), demonstrating effective compensatory growth. Consequently, the LOW group attained a significantly greater final bodyweight. During the subsequent combined-management period (Period 2), the LOW group had lower growth rates but maintained their bodyweight advantage. At 9 months of age, the LOW group produced a heavier greasy fleece (1.67 kg; P < 0.001). The preferential management strategy yielded a net profit of A$6.24 per head across the whole flock, when comparing the production gains of the LOW and HIGH groups combined against the costs of preferentially managing the LOW group, relative to the CTRL group. Implications Preferential management through targeted supplementary feeding and intensive parasite control is an effective and economically viable strategy for improving the bodyweight and wool production of underperforming weaner sheep. This intervention allows low growth-rate weaners to surpass their high growth-rate counterparts.