Effect of Condensed Tannin Extracts on Gastrointestinal Nematodes of Small Ruminants

Experiments were carried out to investigate the effect of condensed tannins on gastrointestinal nematodes. In the first two trials (trial 1 and 2) mature and young parasite naïve sheep under artificial haemonchosis were offered a low protein diet containing varying levels of quebracho extract (QT), a model source of condensed tannins. In trial 1, thirty-five mature rams were assigned to five groups (n = 7); the control group received no QT whereas the rest received feed containing 1, 2, 4 and 8% w/w QT. Trial 2 had four groups of young rams (n =9), which received 0, 2.5, 5 and 8% w/w QT. All animals in both trials received a trickle dose of infective stage larvae (L3; Haemonchus contortus) to the end of the experiment. Faecal egg counts (FEC), feed intake and average daily body weight gain (ADWG) were monitored for about 2 months. Dietary inclusion of QT at the 8% level reduced FEC by 36 and 51% in trial 1 and 2 respectively. This was an indication that young and parasite naïve lambs in trial 2 were slightly more responsive to the effect of QT on FEC than mature sheep in trial 1. Although the effect of QT on FEC in trials 1 and 2 was not statistically significant, negative correlations (R2 = 0.81 and 0.64 respectively) between dietary QT level and FEC were observed. Feed consumption and ADWG were significantly reduced (P < 0.05) by dietary QT, while faecal water content and faecal output increased significantly (P < 0.01).