A Trace Mineral Injection before Joining and Lambing Increases Marking Percentages and Lamb Weights on Diverse Farms in Victoria, Australia

SIMPLE SUMMARY: Optimum trace mineral (TM) status in ruminants is essential for fertility and the survival of the offspring by preventing oxidative stress and improving immunity. The benefits of injectable TM (ITM) supplementation in the lead-up to high-demand periods, such as pregnancy and calving, have been demonstrated in cattle. However, scientific evidence of its benefits for sheep fertility and health is scarce. The objective of this field study was to evaluate the effect of an ITM supplement containing Cu, Se, Zn and Mn pre-joining and pre-lambing to ewes on conception rates, ewe and lamb survival and farm profitability. This study demonstrated that supplementing ewes using ITM before joining and lambing can improve lamb survival, weight at weaning and farm profitability. These results help to understand TM supplementation for animal health, performance and farm profitability beyond the treatment of clinical deficiencies. ABSTRACT: This study was conducted on five commercial farms across Victoria, Australia, between September 2018 and November 2019, where the TM status of ewes was within normal ranges before joining. Mix breed ewes (n = 1484) were randomly allocated to receive either nil treatment (Control) or two injections of an ITM product containing zinc (40 mg/mL), manganese (10 mg/mL), selenium (3 mg/mL), and copper (10 mg/mL); 0.2 mL per 10 kg BW (Multimin(®) plus Copper for Sheep, Virbac (Australia) Pty Ltd., Milperra, NSW, Australia) 30 days before the start of joining and 30 days before the start of lambing. Approximately 90 days after joining, pregnancy status and conception rate were determined by ultrasound. The marking rate was determined approximately four weeks after the end of lambing, and lamb weights were determined at weaning (12 weeks after the end of lambing). In all farms, ITM treatment did not affect the conception rate. The average conception rate was 156 ± 11.0% (p > 0.05). The marking rate of ITM ewes was 9% higher than control ewes (95% Confidence Interval 3–21%). Lambs born to ITM ewes were 2.31 kg heavier at weaning than lambs born to control ewes (p < 0.001). Although not significant, ewe mortality across farms was 1.3% lower in the ITM group than in the control group. On average, ewes treated with ITM pre-joining and pre-lambing produced more and heavier lambs that represent an extra AU$ 2338 per 100 ewes net benefit for the producer. These results help to understand strategic TM supplementation for animal health, performance and farm profitability beyond the treatment of clinical deficiencies.