Influence of different forages on gastrointestinal namatode infections in grazing lambs

Summary

Nematode infections of sheep may be influenced by secondary compounds in the diet, e.g. condensed tannins. A study was performed with 7 groups of lambs experimentally infected with Teladorsagia circumcincta and Trichostronglylus vitrinus. All groups were grazed on clean clover-grass pasture and then moved to paddocks with bioactive forages with either sainfoin (Onobrychis viciifolia) (groups Pre-S and Post-S), chicory (Cichorium intybus, cv. Grasslands Puna) (Pre-C and Post-C) or clover-grass as reference (Pre-G and Post-G). Pre-groups were infected before the move to bioactive forages, whereas all Post-groups were infected after the move. Group Pre-ctrl. was slaughtered for worm counts at the time of the move while the other groups were slaughtered after 5-8 weeks on bioactive forages. The faecal egg counts of pre-groups dropped markedly after the move, and Pre-S showed the fastest decline, by 80% within 3 weeks after the move. The mean faecal egg counts of Post-S was reduced by 40% 4 weeks p.i. compared to Post-G (p<0.01) whereas Post-C was 30-100% higher (p<0.01). T. circumcincta worm counts of Pre-S, Pre-C and Pre-G were 4300, 3200 and 7000 but differences were not significant due to large variation within groups (Pre-C vs. Pre-G: p=0.12). Other worm counts were not significantly different. The study indicates a marked reduction in faecal egg counts when lambs graze sainfoin and a possible anti-parasitic effect of chicory on abomasal worms.