Evaluation of the feeding value of Aries HD perennial ryegrass (Lolium perenne). II. Performance of weaned lambs in summer and autumn

Abstract

The feeding value of Aries HD perennial ryegrass (Lolium perenne) was evaluated over summer (2 Dec 1996 to 12 March 1997) using Romney weaned lambs, with Yatsyn 1 perennial ryegrass as the control cultivar. There were three replicate plots of each cultivar of 0.33 ha continuously stocked with 8 lambs per plot to maintain a mean sward surface height of 6 cm. There was no significant difference in lamb liveweight gain (116 versus 111 ± 5.1 g day−1, P > 0.6) or herbage intake (0.7 versus 0.6 ± 0.10 kg OM day−1, P > 0.5) between Aries HD and Yatsyn 1 lambs. Liveweight gain of lambs (mean of two treatments) decreased as the experiment progressed from 174 g day−1 in December, to 102 g day−1 in January/February, to 76 g day−1 in February/March. Incidence of ryegrass staggers was low with 9% of Yatsyn 1 lambs being affected over late February/early March, which coincided with a peak lolitrem B concentration of 1.37 ppm in Yatsyn 1 pasture, which was similar between cultivars. There was no significant difference in final carcass weight of lambs grazing Aries HD and Yatsyn 1 (14.9 versus 14.6 ± 0.24 kg, P > 0.5), reflecting the similar nutritive value and alkaloid concentrations of the two cultivars over this summer/autumn period.