Endophyte mixture effects on ryegrass staggers in sheep

Epichloë endophytes protect ryegrass from insect pests, but no strain provides both the highest level of insect protection and lowest risk to livestock health. This study examined mixtures of endophytes to find combinations that could mitigate ryegrass staggers in sheep. At Barenbrug NZ, Courtenay, pastures varying widely in sown proportions of perennial ryegrass infected with nea3, nea12 and standard endophyte (SE) were sown in May 2019 and tested with lambs in summer and hoggets in spring 2020. In summer, sown proportions of >65% nea3, <35% nea12 and no SE delayed severe staggers (score 4–5) by 1 week. Alkaloid profiles of these pastures included the tremorgens epoxyjanthitrem I (<0.28 ppm) of nea12 and paxilline (<0.15 ppm) and terpendole C (<1.37 ppm) of nea3. In spring, sown proportions of >65% nea3 and <35% nea12 and/or SE did not induce staggers (score 0–0.1). Those pastures had low concentrations of the potent tremorgen lolitrem B (<0.30 ppm) of SE, epoxyjanthitrem I (<0.39 ppm) of nea12 and paxilline (<0.09 ppm) and terpendole C (<0.41 ppm) of nea3 and SE. The optimal endophyte formulations that minimised staggers across summer and spring were >65% nea3, <35% nea12 and no SE.