I use Aval 4 tub 30-60 days pre calving till I pull the bull. Rest year loose Aval 4. I like the fact calves get into them right away too. I either get it in stress tub (one coop all they carry) or with XPC and I think it really helps digest some crappy forage. Temps have improved but cows are now eating my very mature first crop.
I'm not sold on fly tubs. Feeder price down will be one thing along with longrange wormer we will forget this year.