Three experiments were undertaken to investigate the possibility that forages containing condensed tannins (CT) may affect nematode parasite burdens and their significance in lambs. In the first trial, lambs were infected with a single dose of 15000 Ostertagia circumcincta and 15000 Trichostrongylus colubriformis infective lavae. Those fed Lotus pedunculatus with or without polyethylene glycol (PEG) had lower faecal egg counts, higher liveweight gains and higher faecal dry matters than lambs fed ryegrass with or without PEG (P<0.05). In the second experiment, lambs with a low, mixed natural worm burden were grazed on sulla (Hedysarium coronarium), a CT containing legume, or lucerne, for 28 days. Lambs drenched with anthelmintic and fed sulla grew faster than those fed lucerne (321 v 215 g/day P<0.05) whilst undrenched lambs had similar growth rates on both species (250 v 220 g/day). In the third experiment, heavily parasitized lambs sired by rams selected for low faecal egg count (resistant) or conventional rams (non-resistant) were grazed on lucerne or sulla for 28 days. When anthelmintic drenches were withheld, the non- resistant sired lambs grew faster on sulla than lucerne (231 v 28 g/day; P<0.0001), as did the resistant sired lambs (181 v 72 g/day; P<0.001) respectively. Drenched non-resistant sired lambs grew faster on the sulla than on lucerne and faster than the resistant sired lambs. These results suggest that forages containing condensed tannins may have an important role to play in developing lamb production systems with less reliance on anthelmintic use for parasite control.
Proceedings of the New Zealand Society of Animal Production, Volume 53, , 189-196, 1993
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