The only thing that makes my turkeys bitter is when I take their eggs (someone had to say it)
Since we had a very rough winter this year, the ground was covered with snow, and since alfalfa prices were the same as hay, I have been feeding my Barbados alfalfa, the turkeys have made a game out of eating alfalfa off of the sheep and foraging through their feed. I did process earlier this year and found no unusual flavors in the meat however, the turkeys would forage on their own every chance they could get and they did get corn. I am not up on this myth but I do know that alfalfa contains a significant amount of tannin, (the compound itself is bitter) from what I understand this may affect the ability of the tissues to absorb, which is remedial for many ailments for many animals, ostensibly humans as well. If you are feeding free choice on other foods, I would not worry about flavor, it did not seem to make a difference in my case. It does NOT ruin the flavor of lamb. I am very curious as to others experiences with this.