Feed-Through Fly Control: Which Type Should You Use?
Fly season is upon us, which means it’s time to start plotting their demise. Not only are flies annoying and unsightly, they also spread disease, contaminate pre-existing wounds, and irritate your horses eyes and skin with bacteria. While fly sprays and gear are never in short supply, one option that does not get enough hype is feed-through fly control.
There are two main types of feed-through fly control. The first includes products with Insect Growth Regulators, or IGRs. These are pesticides—usually made with ingredients like diflubenzuron or cyromazine—that have been tested and approved by the EPA as safe for equine consumption.
These products work by killing fly larvae before they have a chance to develop, disrupting the production of chitin- the compound that forms the larvae’s exoskeleton. Since humans and horses don’t produce chitin, we are unaffected by these treatments.
When ingested by the horse, the larvicide travels through the digestive tract and is excreted in the manure- which happens to be where most flies lay their eggs. Once those eggs come into contact with the treated manure, they are unable to develop into adult flies, decreasing the overall fly population in and around your barn. In fact, some studies have even shown up to a 90% drop in fly development after exposure to the treated manure. However, this product works best when fed to all the horses on the property.
Some popular IGR products include:
- Solitude IGR- A popular pelleted option made by Zoetis that can be mixed in with grain or used as a top-dress.
- Farnam Simplify- Even the pickiest eaters enjoy these highly palatable pellets, which are fed just once a day.
Check out these resources for more information on insect growth regulator fly control →
The second category of feed through products are those that do not contain IGRs but instead, active ingredients like garlic, grape seed extract, amino acids, fatty acids, B vitamins, MSM and apple cider vinegar.
Unlike IGRs, these ingredients are meant to be absorbed by the horse and act as a repellant. When ingested, they release a smell form the pores that flies find unappetizing.
For horse owners who prefer more naturally derived ingredients, the following are excellent options:
- Hilton Herbs “Bye Bye Fly”- A garlic derived granule that supports respiratory health and immune function while also deterring flies and biting insets.
- Bug Check- Made by The Natural Horse Vet, this powder contains dried yeast, grape seed meal, and garlic powder for fly repelling, while also incorporating probiotics for skin and gut health.
So, which type should you use this spring?
It depends on whether you're trying to control the fly population or simply protect your horse from bites.
- Horses kept at home or in smaller facilities may benefit more from IGR products, as they help reduce the overall number of flies in the environment.
- On the other hand, non-IGR products are effective for any horse, in any setting, if your goal is to prevent bites.
Regardless of what type of feed-through fly control you choose, the feeding directions are the same:
- Start in early spring for the best results
- Feed daily, preferably to the every horse on the property
- Top-dress on grain or mix in with your horses total ration
While both types of feed-throughs can be effective, the best results come from combining multiple methods of fly control. Don’t underestimate the value of fly sheets and masks—they offer essential protection for your horse’s skin against bites.
It’s also important to clean up any existing (untreated) manure piles before starting a feed-through product, to give your program a clean slate.
