Use of Lotus corniculatus containing condensed tannins to increase lamb and wool production under commercial dryland farming conditions without the use of anthelmintics

Abstract

Two grazing experiments were conducted for 12 and 13 weeks, respectively, over the spring periods of 2000 and 2001 at Massey University's Riverside farm in the Wairarapa (New Zealand) to compare effects of grazing Lotus corniculatus (birdsfoot trefoil; cv. Grasslands Goldie) or perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) dominant pasture during lactation on ewe and lamb live weight (LW), wool production, faecal nematode egg counts (FEC) and dag score. Ewes and their lambs (mainly twins) were rotationally grazed on lotus or pasture ( n = 50) without any anthelminitc treatment at a herbage allowance of 6.5 and 8.0 kg green DM/ewe/days for Experiments 1 and 2, respectively. Total condensed tannins (CT) concentration in the diet selected was 24 to 27 g CT/kg DM for lotus and 1.4 to 1.5 g CT/kg DM for pasture. In vitro organic matter digestibility and metabolisable energy (ME) concentration were higher for lotus than for pasture in both experiments, whilst the concentrations of neutral detergent fibre (NDF) was lower in lotus than in pasture. The LW gain, weaning LW and wool production were consistently higher ( P < 0.001) for lambs grazing lotus, in both Experiment 1 (258 versus 189 g/days; 36.1 versus 30.1 and 1.17 versus 0.98 kg) and in Experiment 2 (247 versus 162 g/days; 31.8 versus 24.1 and 1.17 versus 0.81 kg), respectively. Ewe and lamb dag score were strongly and positively correlated with dag weight ( P < 0.001), and generally increased with time in sheep grazing pasture; while grazing on lotus consistently reduced dag score. FEC in ewes grazing pasture showed a post-parturient rise (PPR) following lambing, whilst ewes grazing lotus had a reduced PPR in FEC. Up to day 70, FEC in lambs grazing lotus was lower than that for lambs grazing pasture, but between day 70 and the end of both experiments (approximately day 90), FEC in lambs grazing lotus increased to similar values as for pasture-fed lambs. FEC was not correlated with dag score or dag weight in ewes or lambs grazing pasture, but these indices were weakly and positively correlated in ewes and lambs grazing lotus, suggesting that lowering FEC on lotus also reduced dag formation. Under dryland farming conditions, the use of Lotus corniculatus (cv. Grasslands Goldie) during the spring/early summer lactation period can be used to increase lamb growth and wool production, whilst eliminating the need for pre-lambing anthelmintic drenching and, probably, reducing the amount of insecticide needed to control flystrike. These effects are probably due to the CT in lotus reducing rumen protein degradability and controlling internal parasites, and to the higher digestibility and voluntary feed intake (VFI) of lotus compared to perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) pasture. The absence of endophyte in lotus may also have contributed to these effects.