The objective of this study was to determine the effect of dry corn (DC) and fermented corn (FC) supplemented to alfalfa haylage (AH) (Medicago sativa L.) on feed intake, digestibility, and nitrogen (N) balance in wether sheep. The study consisted of five feeding treatments incorporating AH alone and AH supplemented with 5 or 10 g of DC (DC5 and DC10, respectively) or FC (FC5 and FC10, respectively) kg^-1 body weight (BW) d^-1 to Suffolk wethers. The DC5 and FC5 treatments were higher in acid detergent fibre (ADF) intake (P < 0.001), neutral detergent fibre (NDF) intake (P < 0.001), and N intake (P < 0.05) compared with the DC10 and FC10 treatments. Both energy sources (DC and FC) and supplemental levels (5 and 10 g kg^-1 BW d^-1) increased (P < 0.05) the digestibility of dry matter (DM) and organic matter (OM), and the digestibility of OM in DM (D value), and decreased the digestibility of ADF (P < 0.05). The DC10 and FC10 treatments had higher D values (P < 0.05) and reduced ADF digestibility values (P < 0.05) compared with the DC5 and FC5 treatments. The FC supplemented treatments had reduced N balances compared with DC treatments (P < 0.001). It was concluded that DC was a better supplement to AH than FC in terms of NDF intake, crude protein (CP) digestibility, and N balance. The main effect of increasing the level of starch supplementation to the diet was a reduced N and fibre intake, as well as N and fibre digestibility, but an increased D value.