Effect of feeding bioactive forages on infection and subsequent development of Haemonchus contortus in lamb faeces

Contrasting dried herbage diets were offered to lambs to evaluate their effects on Haemonchus contortus infection and on subsequent development of larvae in faeces. Artificially infected lambs (n=24, 4 months old) were allocated to one of four treatment groups (n=6) and fed on hay of lucerne (Medicago sativa; Lu), sulla (Hedysarum coronarium; Su), sainfoin (Onobrychis viciifolia; Sa) or wormwood (Artemisia absinthium; Wo) included as 20% in ground lucerne pellets. While voluntary intake was similar, lamb growth rates were notably affected by diet. Additionally, necropsies carried out 30 days post-infection showed that worm burden was reduced by 8 (Su), 13 (Sa) and 49% (Wo) with respect to that found in lambs fed on lucerne, though only the difference with wormwood was significant. Faecal egg excretion expressed on a dry matter basis was also reduced by 22 (Su), 54 (Sa) and 73% (Wo), but differences were significant only for wormwood and sainfoin, which was associated with a decrease in female fecundity. Sulla and sainfoin diets significantly reduced egg hatching rates but increased the percentage of L(3) in the faeces of the host animal, particularly in the case of sulla hay compared to other forages. Consequently, the potential risk of infection derived from faecal excretion could be notably altered. Further work is needed to validate these findings and their implications in an applied farming system.