 The group that got the antibiotic leftovers gained twice as much weight as the control group that had gotten a normal diet. Really? So a huge amount? A huge amount. Doubled their weight gain. Jukes had discovered that when trace amounts of antibiotic were given to chickens, not sick chickens, healthy, normal birds, it doubled their growth rate. Now, I've done quite a bit of lab work, and I can tell you, you simply don't see results that dramatic very often.