Abstract:To investigate the effect of seed origin on the nutritive value of narrowleaf birdsfoot trefoil (NBT, Lotus tenuis Waldst.&Kit.), seeds of 86 NBT populations were collected from plants spontaneously occurring in natural pastures and rangelands located at different geographical gradients of the Black Sea Region, Turkey. Some nutrient contents of these populations regrown under the same conditions were determined. Minimum and maximum values with regard to the crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), Ca, P, Mg, K and condensed tannin contents, relative feed value, Ca P -1 and K (Ca+Mg) , latitudes (digestible dry matter and ADF) and longitudes (CP and Mg) on some nutrient contents and feed values were found significant (P<0.05). The correlations between altitude and NDF, P and Mg or between latitude and P and Mg contents of populations were significant. There were no specific trends in chemical composition and the nutritive value of tested NBT populations due to geographical variation. Thus, the results suggested that all studied geographical populations can be selected to obtain the nutritionally superior forage.-