Calculation of the Mixing Time as a Function of the Dairy Cow Diet Chemical Homogeneity Inside the Mixing Hopper

The objective of the study was to develop and implement a Near InfraRed Spectroscopy (NIRS) based system to determine the optimal mixing time of the Total Mixed Ration inside the hopper of a mixer wagon. To do this, a diode array spectrometer (950–1650 nm range), with a calibration model for predicting the main chemical parameters of the ration, was mounted at the bottom of the hopper of a horizontal self-propelled mixer wagon, close to the unloading belt conveyor, and was integrated in an on-line and real-time measurement system that was activated during the mixing procedure. The optimal mixing time was assumed to be achieved when the stability ratio of the chemical parameters measurement process was < 1.5. Student’s t-tests were used to compare the distribution of the main nutrients in the ration inside the mixing hopper and in the delivered ration. Results showed that the chemical homogeneity inside the mixing hopper was reached on average at 3.31 ± 0.87 min after the last ingredient was loaded. The ration inside the hopper reflected the delivered ration for Dry Matter, Neutral Detergent Fiber and starch (P > 0.05), while exceeded the delivered ration for Crude Protein, Acid Detergent Fiber and ash (P < 0.01) and underfed Ether Extract (P < 0.01). A fine-tuning of the algorithm implemented as well as an adjustment of the NIR calibration for Crude Protein, Ether Extract, Acid Detergent Fiber, and ash is required to improve the capability of the system in evaluating the ration chemical homogeneity.