Effect of sainfoin (<i>Onobrychis viciifolia</i>) on cyathostomin eggs excretion, larval development, larval community structure and efficacy of ivermectin treatment in horses
Joshua Malsa, Élise Courtot, Michel Boisseau, Bertrand Dumont, Pascale Gombault, Тetiana А. Kuzmina, Marta Basiaga, Jérôme Lluch, Gwenolah Annonay, Sophie Dhorne‐Pollet, Núria Mach, Jean‐François Sutra, Laurence Wimel, Cédric Dubois, Fabrice Guégnard, Delphine Serreau, Anne Lespine, Guillaume Sallé, Géraldine Fleurance
Abstract
activity against cyathostomin free-living stages observed in the past. We analysed the effect of a sainfoin-rich diet on cyathostomin population and the efficacy of oral ivermectin treatment. Two groups of 10 naturally infected horses were enrolled in a 78-day experimental trial. Following a 1-week adaptation period, they were either fed with dehydrated sainfoin pellets (70% of their diet dry matter) or with alfalfa pellets (control group) for 21-days. No difference was found between the average fecal egg counts (FECs) of the two groups, but a significantly lower increase in larval development rate was observed for the sainfoin group, at the end of the trial. Quantification of cyathostomin species abundances with an ITS-2-based metabarcoding approach revealed that the sainfoin diet did not affect the nemabiome structure compared to the control diet. Following oral ivermectin treatment of all horses on day 21, the drug concentration was lower in horses fed with sainfoin, and cyathostomin eggs reappeared earlier in that group. Our results demonstrated that short-term consumption of a sainfoin-rich diet does not decrease cyathostomin FEC but seems to slightly reduce larval development. Consumption of dehydrated sainfoin pellets also negatively affected ivermectin pharmacokinetics, underscoring the need to monitor horse feeding regimes when assessing ivermectin efficacy in the field.