Feeding Acacia cyanophylla Lindl. foliage to Barbarine lambs with or without PEG: Effect on the excretion of gastro-intestinal nematode eggs

Abstract

We investigated the potential use of Acacia cyanophylla Lindl. foliage (Acacia), a tanniniferous legume shrub, as biological way to control gastro-intestinal nematode parasitism in sheep. Fourteen Barbarine lambs (12–14 months old, average LW 33.0 ± 4.1 kg) that had not been treated with anthelmintics for at least the last 6 months were housed in individual pens. Seven animals were allocated to control and experimental groups according to their individual faecal egg counts (FECs) and live weight. Dietary treatments were evaluated during four consecutive periods; Period 1 (days 7–22), Period 2 (days 23–48), Period 3 (days 49–69) and Period 4 (days 70–97). Individuals in both groups received roughage ad libitum and 300 g concentrate throughout the trial. The control lambs were given oaten hay and 50 g polyethylene glycol (PEG, molecular weight 4000) was added to the concentrate in Period 4. The roughage given to the experimental group comprised oaten hay in Periods 1 and 4 and fresh (frozen) Acacia in Periods 2 and 3. PEG was included in concentrate during Period 3. Acacia foliage contained about 140 g crude protein/kg DM, condensed tannins (CT, ca. 82 g leucocyanidin equivalents/kg DM). Faecal egg counts were made on samples taken from the rectum of the lambs at the day of transfer from the field station (day 0), then twice a week throughout the experiment. Generic composition of the nematode population was determined by coproculture. In control lambs, the FECs and total egg counts (TECs; daily egg production) were unchanged over the four measurement periods (P>0.05). In the experimental animals, Acacia given in Period 2 decreased FEC (P<0.05) and TECs (P<0.001). Inclusion of PEG with Acacia in Period 3 increased TECs (P<0.01), suggesting the CT were associated with antiparasitic activity. Six nematode genera were identified by coproculture during the four periods and proportions of each genera were similar in control and experimental groups during all experimental periods. This experiment confirmed the antiparasitic activity of Acacia foliage is likely to be due to the Acacia CT.