Altosid IGR Extended Release Bolus delivers horn fly control with the same method utilized in the rest of the Altosid IGR product line, relying on the animal to distribute the active ingredient in the manure. After the bolus is orally administered, it settles into the cow's rumen where it will dissolve over time, releasing the active ingredient, (S)-methoprene, consistently for up to 195 days. This ensures that cows receive consistent, season-long horn fly control. The active ingredient is then passed through to the cow's manure where horn flies lay eggs. By disrupting the horn fly life cycle, it effectively prevents the development of pupae into biting adult flies.