Liveweight gain and wool production of sheep grazing Lotus corniculatus and lucerne (Medicago sativa

Abstract

Two grazing experiments were conducted to compare the productivity of lactating ewes (Experiment 1) and weaned lambs (Experiment 2) grazing swards of Lotus corniculatus (birdsfoot trefoil; cv. Grasslands Goldie), lucerne (Medicago sativa; cv. Grasslands Oranga), and a mixture of lucerne and lotus. Measurements were made of pre- and post-grazing herbage mass, the composition of the feed on offer and diet selected, and of voluntary feed intake (VFI; Experiment 2 only), body growth, and wool growth. From the agronomic measurements, it was concluded that the diet selected was mainly leaf in both experiments. Total condensed tannin (CT) content was 32-57 g/kg DM for lotus, 8-10 g/kg DM for the mixture, and negligible for lucerne (less than 2 g/kg DM). In Experiment 1, ewe wool production and lamb liveweight gain (LWG) did not differ between forages, but ewe LWG was greater on lotus than on lucerne (251 versus 65 g/day; P < 0.001), with the mixture being intermediate (115 g/day). In Experiment 2, VFI (1.76 versus 1.65 kg organic matter (OM)/day; P < 0.05), LWG (228 versus 183 g/day; P < 0.001), wool production (2.78 versus 2.25 kg; P < 0.05), and carcass weight (20.4 versus 17.8 kg; P < 0.05) were greater for lambs grazing lotus than lucerne; lambs grazing the mixture had similar VFI (1.63 kg OM/day) to those grazing lucerne, but wool production (2.49 kg) was intermediate between lambs grazing lucerne and lotus. Male lambs showed a greater LWG response to lotus relative to lucerne (+83 g/day P < 0.01) than female lambs (+15 g/day; P > 0.05). When adjusted for differences in carcass weight, lotus did not affect carcass fatness (GR 13.1 versus 12.8 mm; P > 0.05). It was concluded that Lotus corniculatus (cv. Grasslands Goldie) supported high levels of sheep productivity, with the responses in wool production and superior growth of male lambs in Experiment 2 suggesting that part of the response may be the result of increased protein supply from action of CT in the digestive system. © 1995 Taylor & Francis Group, LLC.