How does protein enter bloodstream?
Proteins will be digested through a number of proteases in the stomach and intestines (pepsin, trypsin, etc) into their constituent amino acids. The amino acids are then absorbed in the small intestine. So any specific proteins you try to put into a pill will be digested into amino acids before being absorbed. If you somehow manage to defeat the digestive enzymes, the protein will simply pass through the digestive tract without being absorbed--the intestines don't have the capability to allow larger polypeptides through.

If you think about it, this is probably a good thing. We don't want random proteins from our food running around in our bodies. It would likely kill us in short order.