Parasite control for livestock can take several forms: chemicals sprayed or wiped topically, ear tags, and even pressed blocks that deliver insect growth regulator along with vitamins and minerals. We have had quite good success for the past 14 years spraying our yaks a couple of time per week with Permethrin 10% insecticide spray. We buy it in concentrate form and mix it up in 1⁄2 gallon pump sprayers. When the yaks come up for breakfast, we lock our ten animals in the corral and spray both sides as they move around. Yes, they get in- stant relief from the biting insects, but this is not a fun job--and heavy rain will wash it all off.