BackgroundThis study was conducted in Fogera District, north western Ethiopia, to evaluate the effect of harvesting stages on biomass yield and nutritive value of oat–vetch mixtures under residual moisture. The experimental plots were prepared thoroughly by plowing the land before sowing. The experiment was conducted using randomized complete block design in a factorial arrangement having two factors with three replications. The first factor, factor A, comprises a four combinations of two forage species (oats and vetches) having two varieties each. The two oats varieties used were CI-8237 and CI-8251, represented as (O1) and (O2) and the two vetch varieties, Vicia villosa and Vicia dasycarpa, represented as V1 and V2, respectively. The second factor, harvesting stage, had three levels which follows the three physiological stages of oat varieties as flag leaf stage (HS1), milk stage (HS2) and dough stage (HS3) in the mixtures. Agronomic performance and forage biomass yield were recorded. Chemical compositions of the forage such as crude protein (CP), ash, neutral detergent fiber, acid detergent fiber, acid detergent lignin, hemicellulose and cellulose were determined. Data were analyzed with general linear model procedure of SAS (version 9.1; 2008).ResultsResults indicated that harvesting stages significantly (P < 0.001) affected most of the agronomic parameters in oats varieties, whereas plant height and number of branches were significant (P < 0.05) in vetch varieties. Significantly higher (P < 0.001) plant height, number of leaves per plant and leaf to stem ratio) were obtained in variety oats CI-8237. Dry matter yield (DMY) and chemical compositions of the forage were significantly affected (P < 0.001) by harvesting stages. More vigor and higher number of branches were recorded in V. villosa, but higher plant height was obtained in V. dasycarpa. The highest mean DMY (4.99 t/ha) and CP yield (0.81 t/ha) were recorded at harvesting stage two (HS2). However, the lowest DMY (3.42 t/ha) was obtained at harvesting stage one. Relatively, the optimum DMY (6.16 t/ha) with maximum CP yield (0.92 t/ha) was recorded from mixture of CI-8237 + V. villosa at harvesting stage two. The fiber components were increased with advanced stage of growth, but CP and ash contents were decreased as the age of the plant matures.ConclusionsProduction of CI-8237 + V. villosa mixture harvested at harvesting stage two would be more beneficial to produce optimum yield and nutritive value and could be recommended in the study area.