Kathy if you read 5 sources, they will tell you 5 different dosages for Tylan. I think there is a safety window if it's in the ballpark. Merck manual I think says 35 mg per kg, my notes tell me 10 mg per kg (or 3-5 mg per pound from another source.) Another site says 100 mg per chicken each day in the drinking water. Here is another supporting the 10 mg per kg for broiler chickens: http://www.ncbi.nlm.nih.gov/pubmed/12448074