Liveweight gain of lambs grazing three forage rapes which differ in total dry matter yield

Abstract

Three forage rape cultivars ('Greenland', 'Spitfire' and 'Winfred') which differed in height and total dry matter production were compared in a lamb finishing system. Groups of lambs were rotationally grazed on one of three forage rape varieties over a period of 8 weeks in a four replicate trial. Lambs were allocated 2.5 kg dry matter (DM)/head/day in weekly breaks. Lambs were shifted and weighed weekly. 'Greenland' (tall) had a higher DM yield (10 vs 7.6 t DM/ha) and carried a higher stocking rate (75 vs 56 lambs/ha), but had a lower utilisation (46 vs 63%) and supported a lower apparent intake (1.17 vs 1.45 kg DM/h/day) and lamb growth rate (146 vs 205 g/day) compared with 'Winfred' (short). Fast lamb growth rates were associated with high intakes of mainly leaf but also high quality stem. Leaf percentage should be a key breeding objective for forage rape breeders and farmers need to consider attributes of forage rape cultivars other than just total dry matter yield. Key words Forage rape, lamb, liveweight gain, dry matter yield, utilisation, quality