After eight weeks of supplement administration, the researchers found that the overall average number of worm larvae in the feces was reduced by 84%. | Photo: iStock

Could adding a supplement to your horses’ feed reduce the worm burden on your pasture? Researchers recently tested an Australian product designed to do just that—and with positive results.

In recent field trials a feed supplement (commercially available in Australia as BioWorma) effectively reduced the “gastrointestinal nematode (GIN) infectivity of pasture surrounding the feces of treated horses,” the researchers said.

The supplement contains spores of the fungus Duddingtonia flagrans IAH 1297. The fungal spores pass through the horse’s gastrointestinal tract unharmed and are deposited in manure. There, they germinate and grow a mass of fungal hyphae—fine rootlike structures—and sticky traps that inhibit worm larvae, ultimately trapping and killing