N. Vahdani - Department of Animal Sciences, College of Agriculture and Natural Resources, University of Tehran, Karaj, Islamic Republic of Iran.
H. Moravej - Department of Animal Sciences, College of Agriculture and Natural Resources, University of Tehran, Karaj, Islamic Republic of Iran.
K. Rezayazdi - Department of Animal Sciences, College of Agriculture and Natural Resources, University of Tehran, Karaj, Islamic Republic of Iran.
M. Dehghan-Banadki - Department of Animal Sciences, College of Agriculture and Natural Resources, University of Tehran, Karaj, Islamic Republic of Iran.

The nutritive value of grass pea (Lathyrus sativus L.) hay was evaluated based on its chemical composition, Gas production, fractioning of protein in CNCPS and AFRC systems, Metabolizable Energy (ME), rumen degradability through in situ technique and in vitro digestibility through Tilley and Terry method. The Crude Protein (CP), Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF) values of grass pea hay amounted to ۲۳۲.۴, ۳۹۷ and ۳۰۰.۶ (g kg-۱ DM) respectively. Condensed Tannins (CTs) and β-N-Oxalyl –L-α, β-diAmino Propionic acid (ODAP) amounted ۰.۲ and ۱۱.۸ (g kg-۱ DM) respectively. Grass pea estimated ME ranged from ۶.۸۶ (MJ kg-۱ DM) to ۱۲.۰۳ (MJ kg-۱ DM) by different methods. Metabolizable Protein (MP) content was found ۵۳۴.۷ g kg-۱ of CP. A high level of CP and MP content followed by a high content of ME along with a high palatability, cause grass pea to be introduced as an alternative to sheep forage in drought conditions.

Condensed tannins, Grass pea, Nutritive value, ODAP, Palatability