Pellets enriched with healthy hay and quebracho are not sufficient to control gastrointestinal nematodes in meat sheep commercial flocks

The emergence of AH multiresistant GIN compromises sustainability of grassland sheep farming worldwide. Plants rich in condensed tannins are an alternative method of parasitism management that is currently being explored. Feed supplementation trials with pellets rich in sainfoin (<i>Onobrychis viciifolia</i>) and quebracho (<i>Schinopsis</i> spp.) were carried out. Three meat sheep farms in western France took part in the study and a total of 4 trials were carried out.During these 21-day trials, the ewes were returned to the sheepfold and half of them received a balanced ration supplemented with 70 g day⁻¹ of healthy hay and quebracho pellets, while the other half received the same ration supplemented with 70 g day⁻¹ of lucerne pellets. Fecal egg counts (FEC) were carried out at the start and end of each trial, and nematode species were identified by real-time PCR after larval culture. At D0, FEC were similar in both groups for all 4 trials. Proportions of species infecting the ewes varied from 1 trial to another: <i>Haemonchus contortus</i> was predominant in summer and <i>Trichostrongylus colubriformis</i> in winter. At D21, there were no significant differences in FEC between groups. Helminthofauna were not significantly different between groups, except for 1 trial where the proportion of <i>H. contortus</i> was reduced in the group supplemented with condensed-tannin pellets. The use of condensed tannins still requires additional studies to be advised as an effective method to manage gastrointestinal nematodes in farm.