Evaluation of quality characteristics in official trials with silage maize varieties in Belgium

Abstract

In the official Belgian trials for silage maize, qualitative characteristics are incorporated in the evaluation criteria for new varieties since 1992 (digestibility) and from 1995 starch. To analyse many samples (> 1000/year) the NIRS method based on in-vitro with cellulase was proposed by the official Committee for the national variety list for the prediction of digestibility. Comparing NIRS digestibility, based on cellulase, with a NIRS calibration developed at the Plant Breeding Institute based on rumen fluid digestibility, a highly significant correlation has been obtained. It is however necessary that after each new harvest a certain percentage of the samples should be analysed in a classical way to validate the calibration equation against a sample set with new genetic material. In contrast to literature data there is no clear 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 content. The correlation between earliness and starch is not very high but still significant. Since digestibility and starch are not well correlated, the incorporation of starch as a new criterion is valuable and it can give additional information about the net energy content of silage maize varieties.