The aim of study was to determine the potential nutritive value of some forages using chemical composition, in vitro gas production kinetics and some estimated parameters. In this study, maize hay-MH, grass hay-GH, alfalfa hay-AH and vetch hay-VH were used. There are significant differences among forages in terms of chemical composition. Crude protein (CP) content ranged from 9.17 to 21.89 %. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents ranged from 45.40 to 57.86% and 28.07 to 36.07%. There are also significant differences among forages in terms of in vitro gas production, kinetics and some estimates of parameters such as metabolizable energy (ME), net energy lactation (NEL) and organic matter digestibility (OMD). The ME, NEL and OMD values of MH, AH and VH were significantly higher than that of GH. The potential nutritive of alfalfa and vetch hay had a significantly higher than those for maize and grass hay when chemical composition, gas production kinetics and some estimated parameters such as ME, NEL and OMD of forages were taken into consideration.