Recently, NIR instruments (Near Infrared Spectrometers) have been used to evaluate the nutritional value of feed. Obtaining the results of the evaluation of the tested feed is much faster and cheaper with them. Unfortunately, the accuracy of these devices depends on the accuracy of calibration of individual feed types according to chemically determined values, the more analyzes included, the higher the calibration accuracy tends to be. In addition, the instruments must be recalibrated. In the contribution, it is shown with several examples how silages are evaluated in terms of nutrition, dietetics and from the point of view of the quality of fermentation.