Buggzo (feed through garlic/diatomaceous earth) and fly predators-- compatible?

I started using Spalding fly predators this year and they’re doing a terrific job at my farmette. I also have 2 horses boarded, and they have a much bigger fly population there. So I started the boarding horses on Buggzo, which is a pelleted feed through of diatomaceous earth and garlic. It seems to be helping.

One of the boarded horses is coming home soon, and of all the horses he’s the most sensitive to flies. I was thinking about keeping him on the Buggzo… but I don’t want to be spending money on fly predators only to kill them. One of Spalding’s competitors SUGGESTS using them in combination and SELLS Buggzo…

http://www.arbico-organics.com/product/buggzo-pellets-feed-through-fly-repellent-horses/natural-insecticides-repellents-horses

I assume Spalding and Arbico are selling the same insect, but I don’t know that for sure.

Even if the diatomaceous earth kills some fly eggs, surely it won’t kill them ALL and there will still be some fly eggs left for the predators to use? I’m going to call Spalding-- but has anyone else used these two products together?

Update- Spalding says it’s fine.

I’d also call Rod, the owner, at HorseTech.com. He is tremendously helpful.