Efficacy of Duddingtonia flagrans spores fed in trace mineral mix to lambs in reducing the development of gastrointestinal nematode larvae in feces.

Providing spores of the nematode-trapping fungus, Duddingtonia flagrans, in the diet of livestock leads to fewer gastrointestinal nematode (GIN) larvae on pasture. The objective was to determine the efficacy of D. flagrans (Df; BioWorma®) fed in a mineral mix compared with a feed supplement to naturally infected lambs (predominantly Haemonchus contortus and Trichostrongylus/Teladorsagia spp.) to reduce the number of GIN larvae cultured. Initially, the efficacy of Df spores was examined in a preliminary experiment in which lambs were fed a control supplement without Df (CON) or with Df (n = 8/treatment) for 7 days. Feces were collected every other day for three coprocultures. Feeding Df led to a 73 % reduction in stongylid third-stage larvae (P = 0.005). In the second experiment, weaned lambs were fed a 12 % crude protein grain supplement with trace mineral added without Df (CON), Df mixed in feed (DfC) or in trace mineral (DfM; n = 8/treatment) for 16 days. Strongylid larval recovery was reduced in both Df groups (P < 0.001), and the third-stage larval recovery was lower in DfM than DfC (P = 0.001). In a field study, similar treatments were used (n = 16/treatment including 2 reps/treatment) using weaned lambs for a 30-day period. The sheep were fed a 16 % crude protein commercial grain mix and a commercial mineral mix; for the DfM group, Df spores were mixed with the mineral mix 7 days prior to feeding. Similarly, strongylid larval recovery was reduced in both Df groups (P < 0.001) but was similar between Df treatments (P = 0.62). No treatment effect on Strongyloides larvae recovered was noted (P = 0.181). Including Df in a trace mineral mix offers promise in control of GIN on pasture or range for flocks that do not offer grain supplements.