When we were testing these bulls the other day, the vet was asking how much grain these bulls got and we got into this discussion. We have not seen any change in the semen quality with our bulls. The vet said that alot of the bulls that he tests that have been pushed for gain will have poor quality semen due to low grade vesicular stomatitis infections putting pus into the semen. He was not sure why but he has seen it and he prefers bulls to be developed slower for that reason.