Variability of digestibility criteria in maize elite hybrids submitted for registration in the French official catalogue

Since 1995, a methodological study has been conducted to determine the feasibility and accuracy of various in vitro digestibility criteria used to estimate genotypic variation in silage maize elite hybrids in the framework of French registration official trials. The study dealt with eighteen early hybrids, amongst which seven official control hybrids and eleven new hybrids submitted for French registration in 1995. Experiments were conducted at seven locations in 1995 and ten locations in 1996. The biochemical components and in vitro digestibility of whole-plant and cell-walls were predicted by near infra-red reflectance spectroscopy. Genotypic variation was significant for all criteria studied. In vitro whole-plant and cell-wall digestibility assessments and the predicted net energy value (UFL) were all notably accurate, discriminant and relevant, with some differences according to the method of assessment. Ranges observed between hybrids tested within the official French registration network were similar to those obtained with control genotypes known for their low or high digestibility values, from previous experiments. Data suggested that, in addition to the usual agronomic characteristics, digestibility or net energy value criteria should also be considered in the silage maize registration process. ((C) Inra/Elsevier, Paris.)