The aim of the methodology is to provide comprehensive information on the use of modern spectrometric methods of near infrared spectroscopy (NIRS) in agricultural production to evaluate selected parameters of feed nutritional value, total mixed ration (TMR) homogeneity, dry matter and starch content in feces and milk quality by native samples in the original dry matter in real time (in situ) and its comparison with the already classical NIRS method for dry samples and with the reference analytical method “wet chemistry”. The NIRS technology for samples in the original dry matter can only be used to analyze feeds for which a calibration equation has been created, which needs to be updated continuously. The result of the analysis depends a lot on the quality of the calibration. Because the method of NIRS technology for samples in the original dry matter is cheap and fast, we recommend using it mainly for a set of a larger number of measurements, especially for comparing samples in terms of their variability.