Effect of condensed tannins extracted from four forages on the viability of the larvae of deer lungworms and gastrointestinal nematodes

The inhibitory activity of condensed tannins extracted from four forage leg ume plants were evaluated by using a larval migration inhibition assay. The first (L1) and third (L3) stages of deer lungworm (Dictyocaulus viviparus) , and the third stage (L3) of deer gastrointestinal nematodes were incubate d with tannins extracted from Lotus pedunculatus, Lotus corniculatus, sulla (Hedysarum coronorium) and sainfoin (Onobrychus viciifolia). The tannins e xtracted from all the forages had inhibitory activity as measured by their ability to paralyse the larvae and inhibit them from passing through sieves . At the highest concentration used (1200 mu g/ml) the tannins extracted fr om sainfoin had the highest activity against ensheathed L1 lungworm larvae (58 per cent), followed by L pedunculatus (45 per cent), sulla (42 per cent ) and L corniculatus (35 per cent) when the larvae were incubated at 37 deg rees C. The same trend, but with lower activities, was observed when the la rvae were incubated at 22 degrees C. Anthelmintic activity against L3 lungw orm larvae was evaluated by measuring the death rate of ensheathed L3 larva e after incubation with condensed tannins for two, 24 and 48 hours at room temperature (22 degrees C). The death rate was significantly higher (P<0.00 1) after 48 hours incubation than after two hours or 24 hours, and signific antly higher (P<0.001) after 24 hours than after two hours incubation. Cond ensed tannins from sainfoin had the highest inhibitory activity followed by L pedunculatus, sulla and L corniculatus. The tannins from sainfoin also h ad the highest activity against L3 larvae of gastrointestinal nematodes, fo llowed by L pedunculatus, sulla and L corniculatus. Exsheathed larvae of ga strointestinal nematodes were significantly more susceptible to the action of the tannins than ensheathed larvae.