In the past 15 years, considerable progress has been achieved in the yield of forage maize and in its resistance to lodging, but this is not the case for the feeding value of the hybrids, as this factor was not taken into account in the registration of new cultivars. The net energy content of modern hybrids is about 0.05 UFL (F.U. for milk) per kg below that of the older hybrids, with values ranging from 0.79 to 0.97 UFL/kg, while the standard value for maize is considered to be approximately 0.93 UFL/kg. There is now a new test, DINAG, based on the enzymatic solubility of the whole plant excluding starch and soluble carbohydrates, which is expected to give the possibility of breeding more digestible plants. The study of cell wall lignification and that of the relationships between the DINAG value and lignification traits will supply physiological explanations to the variations in the digestibility of maize. The first results showed that lines with similar lignin contents may have very different cell wall digestibilities. The molecular approach will be of great interest. Some major QTL’s of lignification and DINAG value were identified, and some of them were mapped in the close vicinity of brown midrib loci. In the near future, forage maize cultivars will be plants with a high digestibility and voluntary intake, and with agricultural features adapting them to a sustainable farming system.