It's a very noble outlook but In reality that's not how it works. By the time that animal has gotten to that stage it will have had several ruts so it has already passed on it's genes, and it's offspring are passing on those genes so shooting something "in it's prime." isn't stopping the good genes getting passed on.
If it is carefully managed there is no reason why these animals shouldn't be taken, especially if the money raised can be used to fund the preservation of the species overall.
The big ivory carrying elephants were shot out by ivory hunters/poachers indiscriminately. Wh