Sheep production and agronomic performance of Lotus corniculatus under dryland farming

Abstract

Lotus corniculatus (lotus) contains condensed tannins (CT; 25-35 g/kg DM), which reduce the microbial degradation of forage protein in the rumen and increase amino acid absorption from the small intestine. In grazing experiments at Palmerston North during the 1990s, sheep grazing L. corniculatus had superior wool production, body growth and ovulation rates (OR) relative to sheep grazing lucerne (Medicago sativa) or perennial ryegrass (Lolium perenne)/white clover (Tritolium repens) pasture. Polyethylene glycol (PEG) drenching studies showed that action of CT was responsible for a component of the increases in wool growth and OR, but not body growth, and increased milk yield in lactating ewes. The 'Massey lotus' programme moved in 2000 to Riverside farm in the Wairarapa, where L. corniculatus is more agronomically suited, and its integration into dryland farming systems is being studied. We aim to develop systems that increase animal productivity whilst also reducing chemical input, notably of anthelmintic drenches. In two experiments conducted over 12 weeks in spring, ewes and lambs grazing L. corniculatus without pre-lamb drenching had lower faecal egg counts (FEC) and lower dag scores than ewes and lambs grazing pasture. Also, liveweight gain (+44%), weaning weight (+26%) and wool production (+32%) were greater for lambs grazing lotus. Weaned lambs grazing L. corniculatus over 14 weeks in summer grew faster than those grazing pasture (298 cf. 201 g/day) when regularly drenched. Reduction of anthelmintic drenching reduced the growth rates of lambs grazing L. corniculatus, but at 228 g/day this was still much faster than those grazing pasture (187 g/day). Lambs grazing L. corniculatus with restricted anthelmintic grew slightly faster than regularly drenched lambs grazing pasture. In addition, ewes mated on L. corniculatus had greater ovulation rates, lambing % and weaning % (approximately 25%) than ewes mated on pasture. Lamb weaning weight was unaffected by the ewes grazing L. corniculatus during mating, but mortality rate during the period from birth to weaning was lower for lambs that were conceived when their dams were grazing lotus. Annual (dry matter) production under grazing averaged over two years (2000-2001), was 9.5 t/ha for L. corniculatus and 8.6 t/ha for pasture. The percentages of annual production that occurred in spring, summer, autumn and winter were 49, 40, 8 and 4%, respectively, for L. corniculatus and 55, 30, 9 and 6%, respectively, for pasture. L. corniculatus has potential as a specialist feed in dryland farming systems for use during mating to increase subsequent lambing percentage and to increase lamb growth while reducing anthelmintic use. The result is more lambs being drafted at an earlier age. Key words: agronomy, body growth, condensed tannins, dry matter yield, Lotus corniculatus, reproduction, sheep, withdrawing anthelmintic, wool growth