I put cylence and ivomec on my cows the weather said it wasn't supposed to rain, three to four hrs later it started to rain. It rain hard for a little while. Cows were out in the pasture. Do I need to reapply?
IF you do, You'll need to wait 3-5 weeks to reapply Bayer makes cylence and cydectin... cydectin is weather proof... I'm not sure about cylence. But I'm pretty sure you'll be fine with both the Ivomec and cylence. After all it says 35 day slaughter hold.... not 35 day slaughter hold Unless It Rains.
My guess would be to gamble that it is fine. If I remember correct, Ivomec says 6 hours??? I would "assume" they give themselves a larger window of safety. Wait a week & bring some manure to your vet. That will tell you. Well, maybe call the vet and ask him how long to wait for a manure sample.