In vitro effect of condensed tannin extract from acacia (Acacia mearnsii) on gastrointestinal nematodes of sheep.

The aim of this study was to determine the inhibitory effects of condensed tannin extract from acacia on the feeding of first-stage larvae (L1) of Haemonchus contortus, Trichostrongylus vitrinus and Teladorsagia circumcincta. The experiment was developed such that the inhibition of feeding for each of the nematode species could be evaluated. L1 recovered from fecal samples from a donor with monospecific infection was incubated in several dilutions of acacia extract (AE). The LD50 was determined for the three species of nematodes. Polyethylene glycol (PEG) was added to all dilutions of AE to inactivate the condensed tannins (CT) from acacia and to confirm their effects on L1. The impact of CT on larval feeding inhibition was detected for all the species of nematodes (H. contortus, T. colubriformis and T. circumcincta). There were differences between the aqueouswater control and CT treated groups (P < 0.01). The LD50 values were 0.043, 0.038 and 0.050 (SE = 0.0024), for H. contortus, T. vitrinus and T. circumcincta, respectively. A difference was detected between the AE and AE + PEG treatments (P < 0.01). Analysis of these results suggested that the direct effect of CT on L1 of the nematodes studied could be used as an alternative means for controlling nematodes in sheep.