An experiment was carried out to investigate the nutritive value of hay of Vicia sativa, Lathyrus sativus and Vicia ervilia cultivated in Ardabil province. Digestibility was estimated through in vitro method. Gas Production (GP) was recorded after 2, 4, 6, 8, 12, 24, 48, 72 and 96 h of incubation. Crude protein contents of the tested hay legumes were (14.99-19.05%), Crude Ash (11.70-13.54%), ADF (29.46-32.66%), Ca (1.111-0.827%), P (0.03-0.06%) and Dry Matter Digestibiliy (56.60-61.46%) respectively. The 24 hr gas production volume for heys of Vicia sativa, Lathyrus sativus and Vicia ervilia were 47.57, 4.14, 41.03 mL/200g DM, respectively with Vicia ervilia hey rendering the highest gas production volume (p<0.001) among the feedstuffs tested. In Vicia ervilia hey, potential gas production (52.23 mL), rate of gas production (0.133 mL h-1), Short Chain Fatty Acids (1.055 mmol), and metabolizable energy (9.66 MJ/kg) were significantly higher than those in Lathyrus sativus (48.29%, 0.104% h-1, 0.957 mmol and 8.97 MJ/kg), and those in Vicia sativa (44.88 mL, 0.106 mL h-1, 0.91 mmol and 8.64 MJ/kg). Considering the different chemical compositions of the tested hay, the values for the traits of: in vitro digestibility, gas production as well as metabolizable energy of feeds were also different and thus significantly and differently affected the degradation parameters.