No one has studied whether gluten from the diet of animals gets into the meat (to my knowledge). I will have to call Dogtor J and ask him about this. He is an avid reader of the literature and may have come accross some studies that I am not aware of. Thanks for the tip.
Clinically, I see many people react to beef, chicken, and fish that are fed grains.
The main issue is the health of the animal. Remember that the cardinal rule of nutrition is that we cannot acheive health eating unhealthy foods. Cows, chickens, and fish were not designed to eat grain as their dietary staples. Doing so changes the chemical composition of the meat. Higher in disease promoting fats and lower in nutrient content.
As far as Bluebonnet's B-12. I cannot comment. They have multiple b-12 products and the ingredients might vary in each of them. I would call the company and ask for an allergen spec sheet.
Have a great weekend!