Animal evaluation of Aries HD perennial ryegrass selected for high digestibility

Abstract

Aries HD perennial ryegrass (Lolium perenne L.) has been selected for increased digestibility in summer and early autumn. It is claimed to be the first commercial perennial ryegrass selected specifically for improved digestibility. The relative performance of weaned Romney lambs over summer was compared using Yatsyn 1 perennial ryegrass as a control cultivar. There were 3 replicates of each cultivar of 0.33 ha initially stocked with 8 lambs/plot (24 lambs/ha). Swards were continuously stocked with lambs with a variable stocking rate to maintain a mean sward surface height of 6 cm. Lambs grazing Aries HD plots consistently achieved higher liveweight gains over the experiment. Liveweight gain was higher on Aries HD than Yatsyn 1 during summer dry conditions 24/1/96 to 4/3/96 (50 vs. 31 ± 7.8 g/ day, P<0.035) and overall (104 vs. 84 ± 4.6 g/day, P<0.103). During summer on average 15% of lambs grazing Aries HD pasture were severely affected by perennial ryegrass staggers compared with 29% of lambs on Yatsyn 1 pastures (P<0.027). Information on pasture quality, alkaloid concentrations, and herbage intake is presented and discussed in relation to the differences in animal performance. Keywords: alkaloids, animal evaluation, Aries HD perennial ryegrass, digestibility, lamb performance, Lolium perenne, ryegrass-endophyte association, ryegrass staggers