top of page

To Use or Not to Use Feed Through Fly Control?

Updated: Aug 29, 2023

It's mid-summer and all of my show horses are surrounding by neighbors with Pigeon Fever! Pigeon Fever, which is a bacterial infection that ironically does not cause a fever, has been endemic to the Southwest United States for quite some time, but may be reaching north into dry climates like Montana due to climate change. I was warned about it when I moved here, but the vaccine is known to be experimental at best, so preventing it in my herd has been 100% about fly control. If you've owned horses for five minutes, you know that FLY CONTROL is a holistic endeavor involving super-human manure management, gallons of fly spray, a revolving door of masks and sheets, and possibly a category of supplement products known as Feed Through Fly Control (FTFC). Having built a super-cement compost bin, slathered my horses with SWAT and fly spray, and covered their faces with masks, it's time to turn to the supplement option. This week, were diving into feed through fly control products to see what's out there, do they work, and should I use them to prevent my horses from getting fly-born diseases?

Here is what we are going to cover:

  1. What are the active ingredients?

  2. How do the available products compare?

  3. Important considerations for feed through fly control products.

  4. Summary- Will I use one next season?

When you Google "fly control supplements for horses", you're going to run into two major categories of products. The first group of products contain various larvicidal chemicals known as Insect Growth Regulators (IGR). This IGR category contain the true "Feed Through Fly Control" products, because insect growth regulators work by entering the horse's digestive system, running the full length of the "tube", and then coming out the other side in the horse's manure. It is there in the manure that IGR products work their magic. When flies land on the manure containing the IGR, the larvae of the flies can not develop an important compound called chitin in their exoskeletons leaving them like wet worms at the end of your fish hook.

The second category of "fly control supplements for horses" do not contain IGR. They contain ingredients such as garlic, grape seed extract, amino acids, fatty acids, B vitamins, diatomaceous earth, MSM and apple cider vinegar. Long, long ago, in my short working student phase, I cared for a horse that was fed copious amounts of garlic to ward off flies. Let's just say, I would NEVER subject any horse or human to that protocol ever again. You have to feed a LOT of garlic to annoy flies, and most supplements are only supplying a few grams. Most of the other ingredients I listed above should already be a part of a well balanced diet (i.e. amino acids, fatty acids, and B vitamins), so I'm not impressed with tiny doses of these nutrients. In my comparison chart below, you can see that these non-IGR products cost quite a bit more per serving than the IGR products, so with cost, efficacy, and common sense in mind, I'm only going to consider the "true" feed through fly controls from here on out.

Let's get back to IGR products...


I found three active ingredients, or chemicals, used in the most popular FTFC products for horses; diflubenzuron, cyromazine, and novaluron. As I type the word "chemical", I know that I'm making a few of you cringe, but I reviewed the EPA Fact Sheets on each of these FTFC active ingredients and they are surprisingly safe. I'll link those sheets below for you to review as well. They all work in the same way; passing through the horse's digestive system to the manure where flies lay their eggs. Eggs can not develop into full fledged flies, and your fly population goes down.

Diflubenzuron seems to be the most common active ingredient in feed through fly control. Farnam puts it in their Simplifly and Equitrol II pelleted horse supplements. Farnam Simplifly seems expensive when you're first browsing ($70 for a 10 lb bucket), but it only costs around $0.44 per day to feed it which is very reasonable as far as ANY supplement category goes. *See the comparison chart below. A company called Central Life Sciences sells diflubenzuron branded as "Clarifly" to feed and supplement companies who then mix it in their pelleted, liquid and block form products. Companies like Tribute put Clarifly in their Essential K ration balancer [CLICK HERE FOR DETAILS], New Generation Supplements puts it in their HorsLic tubs [CLICK HERE FOR DETAILS], and Cargill puts it in their pressed fly control block [CLICK HERE FOR DETAILS]. I love the idea of the fly control in a ration balancer since I use one myself. If you are already using Tribute Essential K, you could simply switch to the fly control product for the late spring and summer months and then go back to the regular during fly-off season. This would save you an enormous amount of time and money. The only thing that I worry about in this scenario is that, being an unpopular and seasonal product, the feed stores would have a hard time managing stocking rates meaning either it's hard to get or bags are old (>8 months from manufacturing).

Zoetis uses the active ingredient cyromazine in their pelleted supplement product called Solitude IGR. According to the EPA Fact sheet, it started out as a feed through fly control for poultry and then moved into cattle and horses. A six pound bucket will set you back $110, but the inclusion rate is small- only 0.5 oz per day per horse- which equates to $0.57 per day. It's a little more expensive than Farnam Simplifly and Formula 707 Multifly. I trust Zoetis as a reputable livestock pharmaceutical company, but they did not respond to my email questions.

Formula 707 DID respond quickly to my email inquiry. Their "Multifly" product is marketed as an equine FTFC with an active ingredient called novaluron. Before we go any further, I want to say, what a HORRIBLE name for a supplement designed to DECREASE the population of flies. I'm sorry, but MULTIFLY implies that the flies are multiplying, not being eradicated! HOWEVER, at $0.37 per day, the Multifly is the least expensive FTFC supplement that you can top dress. Despite the name, this is a product that I would consider given its value, safety, and easy online availability.



  1. Start BEFORE the flies appear! These products will have the greatest efficacy if added to your horse's diet 4-6 weeks before flies start populating your facility.

  2. Make sure that you are getting the serving size correct. Be sure to follow the feeding directions appropriate for your horse's size. If you cut it in half to save money, you'll cut its effectiveness.

  3. FTFC products are NOT replacements for good management such as manure removal, composting, and other fly control measures.

  4. You can cease use of these products during freezing temperatures.


Will I use a feed through fly control in the future? A strong maybe. Considering that fly born diseases are a risk to my show horses, I would consider spending about $80 per year per horse for a 7 month period (here in Montana) to mitigate that risk. I consider it cheap insurance against expensive vet bills. Which product would I use? I would likely start with the Formula 707 Multifly product due to cost value, but would be also consider the Farnam Simplifly. The Zoetis Solitude IGR is more expense and would cost me $120 per year per horse. Overall, I see FTFC products as another arm of my overall farm fly control which also includes composting, regular manure removal, dragging, and fly sprays/ointments. My only question is whether or not a FTFC product will cause a noticeable difference at home despite my neighbors' overstocking rates and poor manure management. To Be Determined!

Want to mix confidence into your horse's diet plan? Schedule a FREE 15 Minute Discovery Call with THIS LINK HERE!

549 views0 comments


bottom of page