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Quick & Easy 3-Step Feed-Thru Fly Control for Horses Guide

A horse with flies on its face.

It never fails….horse owners always spend all winter praying for spring, then we tuck tail and run when the flies arrive. We spend hundreds of dollars on fly sprays, spot-ons, and fly sheets trying to protect our horses from these annoying and potentially dangerous insects, only to find ourselves still struggling to make headway. Adding a feed-thru to your fly control program can help limit the population and make fly season a bit more bearable for you and your horse.

When is the Best Time to Use Feed-Thrus?

Any feed-thru fly control treatment should be administered four to six weeks prior to the beginning of fly season. Why? This allows for the product to reach peak effectiveness and also allows for better control of the fly population during the season. There is no one best time to begin, but experts recommend at least one month prior to fly season. For most people, that means the month of March. However, in humid areas that see flies earlier than others, it’s best to consult with your veterinarian on the best time to start your program. The feed-thru should be continued until the end of fly season.

What Types of Feed Thru are There?

Feed-thrus usually fall into one of two categories: natural or chemical-based.

  1. Natural Feed-Thru

    If you are looking for more of a “natural” approach in your fly prevention routine, look for feed-thrus that contain garlic, thiamine, or apple cider vinegar. These ingredients work by emitting the smell of garlic or vinegar through the pores of the skin. This odor is very offensive to flies. It is important to remember that these types of supplements work like a fly spray does. It repels the flies, but it does not affect the population of the flies.

  2. Chemical-Based Feed-Thru

    The second type of feed-thru fly control is made with ingredients like Dimilin (Diflubenzuron) or Cyromazine. When your horse ingests these ingredients, they exit the horse’s system through the manure. This helps prevent future fly infestations by inhibiting fly larvae development. The result is a smaller population of flies. Feed-thrus containing these chemicals are generally low-risk, high-reward. In small doses (like measured feedings) the chemicals pose a low risk to a horse’s health, but on average they have effectivity rates in the 90th percentile.

What Type of Feed-Thru Will Work For Me?

There are many reasons to choose one kind of feed-thru over the other, but usually, it comes down to one of two things. If you have neighboring farms around your property that are not using methods to cut down on the fly population, you may not see a great difference from using a chemical-based fly control supplement. This is because your neighbor’s flies will find their way to your farm. In this situation, your best bet is to use a natural fly control supplement to repel the flies away from your horse.

If you do not have neighboring farms around your property and are looking to cut down on the fly population, then your best bet would be to go with the chemical-based fly control supplements. The natural fly control supplements will deter flies, but it is important to remember that they are still going to be around being a nuisance to you.


For more information about feed-thru fly treatment for horses, check out the Benefits of Natural Fly Control.

You can also browse Jeffers’ selection of Jeffers’ selection of fly control products.