OK, I want to show my ignorance incase somebody else can learn from it. I have used pour on wormers for years. I went from Ivomectin to Cydectin, to Eprinex. Two weeks ago the vet was out preg checking. When that was over I had a heifer in the barn I thought was losing weight from hardware and asked him to look at her. His first question was how long since you wormed-My response was about 6 weeks prior. His second question was what with-my response was Eprinex. He immediately said she was wormy and we put her in the chute and dosed her with a oral drench called Panacur. We did use Panacur several years ago at vaccine time, and I remembered the cows looking better than ever after that. At this time my entire herd was healthy and after treating the heifer I turned her out like a dummy. One week later a few show some early signs, a few days later its all out in the herd. The day we treated the heifer my vet told me of how the pour-on wormers are becoming less effective and stressed rotating chemistrys. My ingorant butt thought that going from one pour on the the next type was rotating chemistrys. I found out I was wrong. My vet quickly diagnosed the problem both times and even identified the type of worm that was the main problem. Prescibed the oral drench for the herd, which I did promptly. It took about two days for the girls to start firming the stool up good and getting their appetite back.About that time the bulls I moved mid September started acting sluggish and losing appetite. We drenched them yesterday,and just before was the first time I saw the bulls getting the scours.No doubt the same problem, which is something I dont ever remember having here. Our herd is mostly closed except for some donors going to be flushed and a new bull every few years. It is unbelieveable how fast they can loose condition, and from what I understand can kill cattle if not attended to.This morning I feel better that we have a great and knowledgable vet that could make a determination and prescription so quick, and Im thankful for that. The bad thing is my girls are going into the cold season for mostly January calving with loss of body condition. Im afraid if I get them back in shape Im gonna have some big calves? I will definately learn from this and hope it helps somebody else. I also want to mention that the products I used in the past did a good job in my opinion, especially since this is the first occurance like this here. I used the product prescribed by my vet and suggest you do the same, maybe different in your area. The products I used are excellent products if you use them properly, which I did not. My failure to get informed cost me. So like the tv commercial says, dont be like the dumb me, ask your vet. Take my word, prevention is better than reaction!