a couple things to consider,generic products only need to have 80% of the ingredient base in it as the origonal,and all the ivermectin products including the origonal and cydectin, are all made from the same base molecular structure ,dectomax is the only pour on with a different base molecule. so you can't expect different results while continuing to use the same thing, also too many producers try and scimp by on the dosage amounts. i guarantee your cows are way heavier than you think and this is also where alot of the resistance problems come from becuse not enough product is being used. i agree with switching products from time to time as well