The aim of our work was to assess nutritive value of acorn of the holm oak (Quercus ilex: "QI"). The acorn was incorporated at increasing rates in three diets (0, 10 and 20%) as a substitute for a basal diet. Three groups of 7 rabbits, individually caged, received ad libitum one of the three diets. The faecal digestibility of the feed was measured between 46 and 49 days of age. The holm oak acorn (QI) has high starch content: 31% DM but a low protein concentration: 5.6% DM. The digestible energy (DE) concentration of the holm oak acorn estimated by regression was 17.9 ± 1.6 MJ DE/kg DM, corresponding to an energy digestibility of 89.4%. The digestible protein content was 52.4 ± 6.4 g/kg DM corresponding to a crude protein digestibility of 93.9%. The holm oak acorn can be considered as a good source of energy for growing rabbits.