Ryegrass staggers and liveweight gain of ewe lambs and hoggets grazing four combinations of perennial ryegrass and strains of endophyte

Abstract

Ryegrass staggers and live weight gain of Coopworth ewe lambs or hoggets were assessed over four eight week trials (two summer, two autumn) for four combinations of perennial ryegrass and strains of endophyte: Arrow with standard (SE, wild type) endophyte, Trojan with NEA3 endophyte, Trojan with a mixture of NEA2 and NEA3 endophytes, and Rohan with a mixture of NEA2 and NEA6 endophytes. In each trial, three replicates of 10 to 12 sheep were assigned to 0.3 ha plots of each cultivar x endophyte strain combination, with herbage mass reduced from 3-4000 kg DM/ha to 1500 kg DM during the eight weeks. Severe ryegrass staggers occurred in all four trials in Arrow SE, with a mean ryegrass staggers score ranging between 1.65 to 2.8 (0 to 5 scale). Minor ryegrass staggers occurred in Trojan NEA3, Trojan NEA2/3, Rohan NEA2/6 in two of the four trials, but only with a low mean score (<0.4). Live weight gain was lower in Arrow SE than the other cultivars in three of the four trials. Trojan NEA3 had live weight gain that was different from Trojan NEA2/3 (+27 g/head/day higher in Trojan NEA2/3) on one trial only. The perennial ryegrass cultivar x novel endophyte strain combinations Trojan NEA3, Trojan NEA2/3 and Rohan NEA2/6 showed liveweight gain that was similar or greater than the standard endophyte control, and caused minimal ryegrass staggers in ‘worstcase scenario’ conditions designed to induce this.