Forages like alfalfa haylage (AH), which are high in crude protein (CP), need energy-rich supplements to optimize nutrient intake, improve digestibility, and enhance nitrogen use efficiency for better sustainability in livestock production. The objective of the study was to find whether corn or barley is better supplement to AH to achieve these goals. A feeding trial was conducted as an change over design with four treatments, four periods and four animals in each period. The concentrate was fed at a rate of 30 g kg-1 M0.75 wether sheep d-1 and consisted of: (i) 100% corn (CG) (ii) 67% corn and 33% barley (CG67), (iii) 33% corn and 67% barley (BG67), (iv) 100% barley (BG). CG67 had lower dry matter intake (DMI) (P<0.001) but higher dry matter (DM) digestibility (P<0.01). BG had the highest intake of neutral detergent fibre (NDF) (P<0.01), crude protein (CP) (P<0.001) and CP digestibility (P<0.001). BG and BG67 had a higher N balance than CG and CG67 (P<0.001). The results suggest that the quality of the AH and the moderate amount of concentrate used in this study make the addition of barley to AH-based diet more beneficial in enhancing sustainability in sheep nutrition than the addition of corn.