Effects of Condensed Tannins (CT) on crude protein availability in sainfoin hay was investigated according to most popular ruminant feeding systems. Different treatments including Polyethylene Glycol (6000 MW), sodium hydroxide, sodium bicarbonate, potassium permanganate, wood ash, water and urea, were applied for deactivation of CT Crude protein fractioning was determined using nylon bag technique, AFRC and CNCPS systems. Total phenolic compounds, total tannin and condensed tannin content of control hay were 39.4, 38.5 and 21.3 g/kg DM, respectively. PEG and water treatments resulted in higher CT deactivation values as compared with other treatments. Ruminal crude protein degradability, effective degradability and metabolizable protein content, in sainfoin hay, significantly increased with tannin deactivation. Condensed tannin deactivation, caused the reduction of C fraction in CNCPS while increasing crude protein availability. It can be concluded that deactivation of condensed tannins could lead to an increase in crude protein availability in sainfoin hay. Nonetheless PEG, water and wood ash are the most effective in increasing nitrogen availability. No chemicals are employed in water treatment, it benefits from economic justification and ease of use, and is finally concluded as a low cost practical procedure for the processing of sainfoin on the farm.