The effect of condensed tannins from seven herbages on Trichostrongylus colubriformis larval migration in vitro

The effects of condensed tannins (CT) extracted from seven forages on the m otility of the economically important nematode, Trichostrongylus colubrifor mis (Giles, 1892), were evaluated by using a larval migration inhibition (L MI) assay. The assay involved incubation of third stage (L3) exsheathed T. colubriformis larvae with CT extracted from Lotus pedunculatus, Lotus corni culatus, sulla (Hedysarum coronarium), sainfoin (Onobrychis viciifolia), Do rycnium rectum, Dorycnium pentaphyllum and dock (Rumex obtusifolius) acid m easurement of larval migration through nylon mesh with a 20 mu m pore size. At 100 mu g ml(-1), CT from L, pedunculatus L. corniculatus, sulla, sainfo in, D. rectum, D. pentaphyllum and dock inhibited 20%, 10%, 15%, 25%, 28%, 32% and 27% of the larvae, respectively from passing through the sieves com pared to controls (no CT added). Al 1000 mu g CT ml(-1), CT purified from D . pentaphyllum had the highest inhibitory activity (63%) against 1-month ol d larvae followed by sainfoin (59%), L. Pedunculatus (57%), D rectum (53%), dock (50%), sulla (40%) and L. corniculatus (37%). Seven-month old larvae were more sensitive to the action of CT than 1-month old larvae (P < 0.001) . Addition of 2 mu g polyethylene glycol ([PEG] per mu g CT; to remove the effect of CT) eliminated 81-93% of the CT activity (P < 0.001) compared to incubations without PEG. The impact of CT on larval migration suggests a po ssible role for these plants in ruminant diets as a means to reduce depende nce upon proprietary anthelmintics.