I use valbazen because it is easier on the hens. I have started at 4 months and will reworm again in two weeks. I will then wait until they start to have a full molt for the next worming. I try to do it once or twice a year. The valbazen starves the worms so they do not all die at once and overwhelm their systems. I give the smaller hens 1/4 cc and the larger ones1/2 cc. Valbazen kills all kinds of worms. This is given by mouth. While the other wazine only kills one kind of worms. Its more expensive but much better for my babies. Gloria Jean