The flies are coming: Feed-through options to keep flies under control

Apr 14, 2020

What are the feed-through fly control options available on the market and how do they work? Jon Albro discusses the options available for livestock producers and explains why you can’t afford to wait to start your fly control program this spring.


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Tom:    This is Tom Martin and I'm talking with Jon Albro, Nutritionist with CRYSTALYX® Brand Supplements. Thanks for joining us, Jon.

Jon:    Thank you, Tom.

Tom:    So, Jon, warm weather is here in some areas of the country and is on its way in other areas. And one thing we know is that with that warm weather comes those annoying flies. Can you talk to us about the economic impact that flies have on the livestock industry, and how do producers know they have a problem that they need to take care of and address?

Jon:    Yeah, I sure will, Tom. It's an estimated number, and the numbers vary somewhat. And I've seen numbers off and on over the last 20 years or so, and it's a big number, as far as the actual losses are concerned. With the horn fly infestation, the losses are upwards of a billion dollars for the cattle industry. And with stable flies and horn flies, we're looking at, you know, under half a million or even around a quarter million dollars annually for face fly problems. So, the economic impact is real, and we don't often think about it that way, but the problems that are seen from excess flies or bad fly infestations on cattle really relate to poor performance due to disrupted grazing patterns and, also, blood loss from the biting insects and from just overall nuisance and irritation from the insect, from the flies that can cause these performance problems.

            So, you can usually tell you have a problem just by visual observation. People can go out, they can observe the behavior of the animals. They can actually see a lot of flies on the animals. And some of those behavioral signs might exist, such as cattle stomping or fighting flies with their feet, constant tail switching, throwing their head back to fight flies off over their shoulders, and then also, a classic symptom is when cattle start to bunch together in pastures. Sometimes, we see that in high spots, where they're trying to get a little bit of a breeze in the wind to help relieve their stress from the flies, or maybe even bunching into the corners of pastures.

Tom:    Well, what can cattle producers do to control excessive flies in their herd when it gets bad like that, and are there options currently on the market for feed-through fly control compounds?

Jon:    Yes, there certainly are, and there have been for a lot of years. There are numerous different ways that people can implement fly control — through insecticide, through dust, through sprays, through oilers, through tags, etc., but feed-through fly control measures or programs have been available for a long time and are very popular. And there's really three main products on the market. There's a compound called Rabon® oral larvicide that’s been around for decades and decades, and another one called Altosid® that just gets the horn fly, and it's been around for a long, long time as well. A newer one that’s made by the same company is called ClariFly®, and that does have a little more broad-spectrum (usage) than its relative, Altosid, but they've been around a long time. They work very well, and Tim Clark had a blog here about three weeks ago that talked a lot about those products and about the different flies that we're dealing with.

Tom:    How do these compounds actually work once they're consumed by the cattle — and are they absorbed by the animal, or how do they actually control flies?

Jon:    Well, they're called feed-through fly control measures for a good reason, and the reason that they're called feed-through is because they simply pass right through the digestive system into the manure. They’re inert compound, meaning they don't get absorbed in the bloodstream; they just pass right through. And all three of them work on breaking the life cycle of the flies. Flies will use fresh cow manure as a place to lay their eggs. That is especially true for what we call pasture flies, like the horn fly and the face fly, whereas as a table fly and house fly and other flies obviously can lay eggs in other organic matter, but the fresh manure is preferred by especially those first two I mentioned, the face and the horn fly. And it doesn't get absorbed; it goes right through their system. It works in the manure, and as those flies lay their eggs in the manure, the egg hatches into a larva, and the larva stays where the fly control is actually being applied.

            In the case of Rabon, it actually comes in contact with the larva and kills the larva. That's why Rabon is called an oral larvicide. And Altosid and ClariFly work a little differently — they are considered insect growth regulators, albeit ClariFly is also considered a larvicide as well. And they basically act on the larva stage and the pupa stage to help prevent them from developing into the adult flies. They help break down the exoskeleton, in the case of ClariFly, and in the case of Altosid, it just mimics some of the natural biochemicals that are responsible for the larva to develop into the pupa stage and then on to an adult, and then, (it) interrupts that cycle and prevents them from developing. So, we're really talking about controlling the life cycle on the fly population.

Tom:    So, Jon, when should producers start their fly-control feeding program, and how long do they need to feed them after that?

Jon:    That's a really good question, and you'll get a lot of different answers in talking to a lot of different people. It's probably more of a function or more important to think about the time of the year and the weather and geography versus just the animal itself. These compounds, being feed-through, get into the manure relatively quickly because the passage rate of a beef animal, for example, on pasture is relatively short. It's going to be within 1 to 3 days, depending on the quality of forage. So, it's going to get in the manure pretty fast. But again, it's more dependent on weather and geography.

            If you look at a map — and there are some good maps out there on some of these websites that talk about these different compounds — it will show you that, in California through Texas and the deep South of the United States, they can be as early as March 1, on average. Then, if you look at the Pacific Northwest through the Central Plains and the Midwest of the U.S., it's more like mid-April or about right now. And if you get into the northern tier of the States and into Canada, that date moves further out, to about May 15. So, you know, another rule of thumb is if cows are out there on pasture already, it’s a good idea to start a couple of weeks ahead of time, before you have a fly problem. And the theory here is that you want to have these compounds in that manure in the pasture, in any manure that would harbor a good environment or a friendly place for the flies to lay their eggs — even though flies do prefer to lay their eggs in really fresh manure, especially the horn fly. They lay in very, very fresh manure. But two weeks is a good rule of thumb before the flies really become a problem.

Tom:    Well, what does it actually look like when observing animals? In other words, can producers expect 100% of flies to disappear after using the feed-through fly control program, like you explained?

Jon:    Yeah, I think if people do expect that, they're going to be disappointed, because one thing you really need to remember about these fly controls is just that: they are a control measure. They're not an eradication measure. So, there’s still going to be some flies, even with a very good program or several different programs incorporated together. We just want to keep that population at or below an economical threshold. And for horn flies, the data showed that this is around 100 to 200 flies per animal. And it’s probably not very practical, or pretty hard, to try to count the number of flies there might be on an animal, like you would, say, if you’re a researcher in entomology, but there are some good visual illustrations that can give us some ideas on what this looks like. We have a good illustration of what exceptional fly control is, all the way out to poor fly control. We have some good illustrations of this in the CRYSTALYX supplement data, on page 7. So, we just want to keep it under that threshold to where 100 to 200 flies, for example, for the horn fly, would be considered pretty good control, and below that number, that's really going to cause a lot of economic damage.

            So, effective fly control often incorporates more than one control method. Even the manufacturers of these compounds will suggest you have more of an integrated approach, where you might also use some sprays or some other compounds as well, at different times. I do like to joke to customers that the only way to get 100% fly control is to do it in the wintertime, when there aren't any flies, after they all freeze.

Tom:    All right. Well, we've talked about the different fly control compounds and how they work. Can you explain how they're delivered to cattle, and can they be fed to other species as well?

Jon:    Yeah. Well, our main products are all labeled and developed mainly for cattle. However, we do have some products that are labeled and can be used for horses as well. So, these are summer products that are going to be fed on pasture, and they are very easy to use in the CRYSTALYX formulas because of just the overall CRYSTALYX delivery system, the BioBarrel® biodegradable containers, our real popular container for the summer-type programs. We do use that or take advantage of that in a lot of cases.

            But again, Rabon and ClariFly can also be used effectively with horses. And we do have a Stable-lyx® horse product available with ClariFly that is specifically formulated for horses, and that's gaining popularity. And I will also take this opportunity (to say) that, with that product, we also have that available now in a new container size. It's a 33-pound flat-back pail, and that's going to, hopefully, be very popular, and we're just introducing that this month. We also have that stable formula with ClariFly available in 60-pound containers, as well as our traditional, larger-sized plastic and steel containers.

Tom:    Why is CRYSTALYX specifically such a good method to deliver these compounds?

Jon:    That's a good question, Tom, and one that’s important when you really think about how these fly-control compounds work. They work in the manure, and they have to be there every day. So, it's got to be going through the animal system so it’s shed in the manure every day. Because if it’s not, there's going to be manure patties out there that will harbor a favorable environment that will reproduce or not stop the fly lifecycle. So, that Rabon or that Altosid or that ClariFly has to be in that manure for it to be effective. You need a good vehicle to deliver that supplement consistently and to a large percentage of the herd, and that's where CRYSTALYX really shines because it is palatable and it is consumed very predictably, and we know we can get it into a high percentage of the animals. And Tim Clark mentioned this in his blog as well, but I think that’s a key point in effective fly control and the feed-through program: you have to have it in a supplement that gets consumed correctly.

Tom:    There seems to be more discussion and popularity around using garlic in fly management programs. Explain why that is — and does CRYSTALYX utilize garlic?

Jon:    Yes, we do. We have had a product available in Canada for about the last three years, and this year, we’ve introduced that same formula with a slightly different name here in the U.S. It’s a product called CRYSTALYX Mineral-lyx® with garlic, or it’s called Mineral-lyx® GFR.

            The acronym GFR stands for garlic fly repellant, and this is important. We’ve been talking about fly control up until now. We’ve been talking about how the insecticide versions of feed-through fly control all work in the manure, and garlic is a little different. First of all, it's not an insecticide, so it is preferred or has (generated) some interest by people who are looking for alternatives to, you know, more insecticide-type compounds that would be used. So, there's some growing popularity there, some growing interest there. But most of all, garlic, what we do know about it is that it is a compound that has a very strong odor, and it's not really until the garlic is actually broken down — you know, you can take a garlic clove and put it in your hand and it doesn't have a lot of odor, but if you take a knife to it and chop it up and then put it in your hand, you're really going to smell it. The same is true for, say, an onion. So, once you start to break it up, that's when those compounds start to get released. There is an active ingredient in garlic called allicin that, when it breaks down, it breaks down into some disulfide compounds, and those basically come back out of the animal through the skin or through the lungs, where it’s excreted through the breath or the breathing process. And those compounds have an order that are said to have an effect to repel insects. And so, that’s where the fly repellent factor is with garlic, is in that odor.

            There's some research out there — albeit, it would be great to see more, and I think there is more being done — but there is some research out there. One study that we like to talk about came out of Canada a few years ago where they actually fed garlic and a mineral and compared that to some minerals that didn't have garlic, and they saw about a 50% reduction in the fly counts on the animal. So, that was promising, and I think there's going to be more interest in this compound as we go forward.

Tom:    So, Jon, where can producers go to learn more about CRYSTALYX fly control products?

Jon:    You can always go to or visit your local CRYSTALYX dealer — and read our blogs. There’s some great information there.

Tom:    We’ve been talking with Jon Albro, Nutritionist with CRYSTALYX Brand Supplements. Thank you, Jon.

Jon:    Thank you, Tom, for a nice visit.

Tom:    You bet.