Mitigating the impacts of weather on lamb survival in Southern New Zealand

Increased fecundity and improved feed management have doubled the number of lambs born in any threeday period in spring since 1990. Four farmer catchment groups were engaged to investigate options that farmers may use to reduce the impacts of weather at lambing time. After workshops identified potential mitigations, a lamb survival model was developed using data from the literature. This was applied at daily time steps to weather data over a 20-year period from 1980-1999, with chosen mitigations added to investigate their impact. Direct intervention by improving pre-lambing ewe nutrition increased live lambs by 7-8% (P<0.05). Policy development strategies to provide shelter increased live lambs by 8 and 17% with reductions in wind speed of 50 and 100% respectively (P<0.05). These results were consistent across all environmentstested. Increasing fecundity increased the net number of lambs at docking, though also resulted in a greater number of lamb losses. Spreading risk by spreading lambing did not alter the net long-term lamb survival rate. Provision of shelter, both before and during lambing, and ensuring adequate pre-laming ewe nutrition were most effective at consistently improving lamb survival in all the environments tested.