A. H. Azaizeh, T. A. Glasser and A. Marcovics

Gastro-enteritis caused by infection with gastro-intestinal nematodes (GIN) is widespread among goats in the Middle-East. It is characterized by extreme emaciation, diarrhea, and mortality. In a 2-year survey, we observed that the Damascus and Mamber breeds of goats that graze on brushland rich in lentisk (Pistacia lentiscus L.) had very low fecal egg counts (FEC). Lentisk contains 20% polyethylene glycol (PEG, MW 4,000)-binding tannins on a dry matter basis. We tested possible mechanisms of protection against GIN. In a series of in vitro experiments, we showed that ethanol 70% and, to a less extent, water and ethanol 100% extracts of lentisk prevent exsheathment of L3 larvae, thus impairing nematode maturation to the egg-producing adult stage. In addition, we showed that feeding lentisk foliage to young goats infected with mixed GIN species resulted in a drastic decrease in FEC (241 vs. 1293, P < 0.001; n = 14). When goats were administered daily 20 g of PEG (which binds to and thereby neutralizes the tannins), the effect of lentisk on FEC was approximately halved to 705 epg. This suggests that tannins are not the only anthelmintic moiety in lentisk. The daily intake of tannins needed to eliminate fecal egg excretion was 1 g·kg BW-1 d-1. After lentisk feeding was stopped, FEC returned to the control level, implying that the effect of lentisk on GIN was suppressive but not lethal. Our data suggest that daily ingestion of lentisk—5 to 15% of DM ingested—prevents egg formation and possibly larval maturation all year-round, resulting in effective control of GIN populations. This seems to be a passive mechanism, and not an active mechanism of adaptive feeding behavior to a worm challenge.