Lolium Endophyte and Sheep Performance on Perennial Ryegrass Cultivars

Some effects of l&m endophyte (Acremonium lolioe) on sheep production were evaluated using pure swards of h igh (SO%>) and low (< 5%) endophyte Nui and Ar ik i ryegrass. The proportion of infected t i l lers in high endophyte treatments increased by 19% in 15 months. Ryegrass staggers occurred on both high endophyte ryegrasses being sl ight ly worse on Nui . The peak ryegrass staggers outbreak did not coincide with peak endophyte mycelium concentration in ryegrass plants. Hoggets grazing the low endophyte ryegrasses had a 1.6 kg advantage in l iveweight gain in spring, when al lowances were equal , but fewer sheep grazing days. In summer and autumn sward damage by Argentine stem weevil , drought and over-grazing eliminated low endophyte Ariki treatments and reduced herbage production from low Nui to 70% of high endophyte Nui. Ti l ler densit ies in low endophyte treatments were 28% of those in high endophyte treatments. High endophyte Ariki had the highest overal l production: 7.8 t /ha of herbage and 15 kg/head l iveweight gain compared with 6.9 t /ha and 12.5 kg/head for h igh endophyte Nui and 4.7 t /ha and 9 kg/head for low endophyte Nui. Differences in production due to endophyte highlight the need for caution in interpreting results from trials when endophyte status of ryegrass is unknown.