The objective of this study was to determine the effects of condensed tannins (CT) and a crude extract containing sesquiterpene lactones (CSL) extracted from chicory (Cichorium intybus) on the viability of the first (L1) and third stage (L3) larvae of deer lungworm, Dictyocaulus viviparus in vitro using the larval migration inhibition (LMI) assay. The CT and CSL immobilised larvae and inhibited their migration through 25 mm nylon mesh sieves. Incubation of L1 larvae in rumen fluid (collected from deer fed pasture) containing 100, 400, and 1000 mg CT/ml, inhibited 12%, 28% and 41% of the larvae from passing through the sieves, respectively while the incubation of L3 larvae with rumen fluid containing the same concentrations inhibited 26%, 37% and 67% of L3 larvae from passing through the sieves, respectively. CT were more effective (P < 0.001) at reducing the viability of lungworm L1 and L3 larvae when added to the rumen fluid (pH 6.6) than when added to the abomasal fluid (pH 3.0). L3 larvae were more sensitive to the action of CT than L1 larvae. Addition of 2 mg polyethylene glycol/mg CT eliminated most of the inhibitory effect of CT against L1 and L3 larvae especially during incubation in rumen fluid. The CSL extract showed similar inhibitory activity in both fluids, indicating that this extract was not affected by the pH of the fluid, and they were more effective against L3 than L1 larvae.
Proceedings of the New Zealand Society of Animal Production, Volume 60, Hamilton, 26-29, 2000
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