EVALUATION OF QUALITY CHARACTERISTICS IN OFFICIAL TRIALS WITH SILAGE MAIZE VARIETIES IN BELGIUM

In the official Belgian trials for silage maize, qualitative character istics are incorporated in the evaluation criteria for new varieties s ince 1992 (digestibility) and from 1995 starch. To analyse many sample s (> 1000/year) the NIRS method based on in-vitro with cellulase was p roposed by the official Committee for the national variety list for th e prediction of digestibility. Comparing NIRS digestibility, based on cellulase, with a NIRS calibration developed at the Plant Breeding Ins titute based on rumen fluid digestibility, a highly significant correl ation has been obtained. It is however necessary that after each new h arvest a certain percentage of the samples should be analysed in a cla ssical way to validate the calibration equation against a sample set w ith new genetic material. In contrast to literature data there is no c lear tendency that NIRS determination over-estimates the digestibility of early varieties or under-estimates late varieties. The results of the NIRS starch analyses give valuable information about the ear conte nt. The correlation between earliness and starch is not very high but still significant. Since digestibility and starch are not well correla ted, the incorporation of starch as a new criterion is valuable and it can give additional information about the net energy content of silag e maize varieties.