Preliminary investigations of the anti-nematode activity of Acacia cyanophylla Lindl.: Excretion of gastrointestinal nematode eggs in lambs browsing A. cyanophylla with and without PEG or grazing native grass

The potential use of Acacia cyanophylla Lindl. (acacia), a tanniniferous shrub species, as a biologic way to reduce gastro-intestinal parasites was examined in grazing Barbarine lambs. Three groups each of 10 lambs were allocated to one of the following dietary treatment according to a cross-over design: grazing native pasture free of acacia and other woody species (grass group), grazing acacia (acacia group), and grazing acacia after daily oral administration of 40 g polyethylene glycol (PEG mol. weight 4000) (acacia plus PEG-group). PEG, a potent deactivating agent for condensed tannins, was mixed in water (1 kg in 2 l of water) and administered orally. Animals received daily at 8:30 h 300 g concentrate, and were then allowed to graze in the pasture or in the acacia plantation from 10:00 h to 16:00 h. Oaten hay (500 g) was distributed to lambs in the barn at 16:30 h. Each of the three experimental periods lasted 4 weeks. When lambs were on acacia diet they showed a significantly lower mean faecal egg counts (FECs) than those on grass, 849.1 ± 453.6 epg and 1001.8 ± 511.8 epg, respectively. The addition of PEG to the acacia diet resulted in an increase in the daily weight gain and plasmatic uraemia concentrations to levels similar to that in the case of grass. However, the FECs (863.4 ± 434.6 epg) were not increased by comparison to acacia group.