COMPOSITION AND NUTRITIVE-VALUE OF WHOLE MAIZE PLANTS FED FRESH TO SHEEP .2. PREDICTION OF THE IN-VIVO ORGANIC-MATTER DIGESTIBILITY

In vivo trials on sheep carried out in France in 1987 and 1988 run by INRA, AGPM, ITCF and breeders led to prediction models far in vivo organic matter digestibility coefficient of whole plant maize used for silage. The new equations account for 60 to 70% of the variability observed in the in vivo digestibility values. It is difficult to improve these results when we add variation sources: those from the location and plant diversity, and those from experiments on animals and laboratory methods. Near infrared spectroscopy (NIRS) can replace laboratory measures to estimate each of the chemical constituents and in vivo digestibility. These results are used to research the best laboratory prediction reference methods. Direct determination by NIRS of in vivo organic matter digestibility is feasible but at present the data basis does not involve all variation sources and might lead to prediction errors. To improve NIRS performance, we have to standardize the reference method at an international level and set up a wider data base.