@CrealCritter .... the pour on ivermectin is just that, ready to go pour on. No water, no mixing. Are the calves looking wormy? Any reason to think they need to be wormed? We don't often ever worm in the cold weather as it is hard on their systems.... only do it if we think they really need it. And then do it on as warm a day as you are forecast, preferable with no rain or snow or "weather" (precip) for at least 24-48 hours. When we do worm, we try to do it about 48 hours BEFORE we move them to a new pasture so they shed the worms and eggs out on the old pasture and they don't get reinfected as fast. But we don't do much worming now except for bought animals, and sometimes the feeders when they are where we are able to move them a couple days later to clean ground. It is harder to use pour on when they have a long hair coat (winter hair). You should basically part the hair down their backbone and get it on their skin. So that is a judgement call on your part. Many people worm as matter of course... we don't.