The JustiFLY Feedthrough Insect Growth Regulator Supplement is great for control of horn flies, stable flies, house flies and face flies in the manure of beef and dairy cattle. It is a nutritional supplement containing diflubenzuron to be fed continuously to cattle throughout fly season. Cattle simply ingest the larvicide as the feed on the treated feed or mineral. This cost-effective feedthrough growth regulator passes through the animal and starts to work on flies in the cattle manure. with this highly-effective insect growth regulator, you can control flies around your cattle with no cow work required. No more oily insecticides, pour ons, dust bags, sprays, or ear tags.