In general, dairy sheep are fed in large groups that receive the same diet based on the average group milk yield (MY), which is increased by approximately 15% and 25% to cover the energy and protein requirements respectively of part of the high-producing ewes, according to the French INRA system recommendations. Despite this, some of the highest producing ewes are still underfed, especially in terms of energy. This experiment was designed to measure the effect of increasing the amount of energy supplement on milk yield, milk composition and forage intake. Three groups of 16 multiparous Lacaune dairy ewes (DIM mean +/- SD: 40 +/- 1.5) producing 3.4 +/- 0.29 L/d, were balanced in terms of MY, milk composition, body weight (BW: 74.7 +/- 8.43 kg) and body condition score (BCS: 2.7 +/- 0.26). During three periods of three weeks (P1, P2, P3), groups were fed a basal diet based on a mixture of herbage silages and good quality hay (173 g CP/kg DM) offered ad libitum. A protein concentrate was offered at a constant level (0.34 +/- 0.034 kg DM/d/ewe) to cover initial protein requirements. Barley grain was offered at three average levels (kg DM/d/ewe): medium (M, 0.478), high (H, 0.667) or very high (vH, 0.883). The three groups (MMH, MHH, MvHH) received the corresponding amount of barley in the three successive periods: in P1, 0.485 for the three groups, in P2, 0.470 for MMH, 0.672 for MHH and 0.883 for MvHH, and in P3, 0.661 for the three groups. Forage and concentrate dry matter intake were measured each week over five days; milk yield and composition (total fat, protein and urea content) were measured once a week; and BW and BCS were measured every two weeks. Modifying the amount of concentrate (P2, P3) gave no significant (P<0.05) difference between groups for MY, milk composition, BW or BCS. In P2, increasing the level of barley led to a high substitution effect with a decrease of the forage dry matter intake. In P3, increasing or decreasing the amount of barley moderately decreased or increased the forage. Taking into account the whole experimental period (P1-P3), increasing the level of barley did not improve (P>0.05) MY, but slightly increased (P<0.05) BW and BCS. In conclusion, increasing the amount of energy of high-producing dairy ewes fed high-quality forage ad libitum, reduces the forage intake, did not improve MY or change milk composition, but increases BW and BCS.Highlights• Milk yield is not increased in high-producing dairy ewes fed above energy requirements.• Milk composition is not modified when energy requirements are exceeded.• Increasing concentrate decreases forage intake.• Current INRA equations predicting intake capacity and substitution rate remain valid.