4 weeks ago, I started my ladies on Terramycin (3/8 tsp per gallon) for CRD. They were on it for 7 days straight, after which no one was coughing. 2 weeks ago, I started hearing the random cough again. As the days went on, the coughs became more frequent, so, I started them on another round of Terramycin. Today is day number 8 of the treatment but everyone is still coughing. I was planning on doing 14 days on Terramycin but shouldn't the coughing have stopped by now? Should I switch over to Tylan instead? I've also seen some posts for using Vet Rx as treatment. I'm not sure what the appropriate next step is. Any help would be most appreciated!!