LIVEWEIGHT GAIN AND WOOL PRODUCTION OF SHEEP GRAZING LOTUS-CORNICULATUS AND LUCERNE (MEDICAGO-SATIVA)

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.