PORTABLE NIR: A NEW TOOL FOR EVALUATING TMR MIXING QUALITY?
Advances in portable near-infrared spectroscopy (NIR) may provide another way to evaluate TMR consistency. Portable NIR instruments can rapidly estimate feed composition without sending every sample to a laboratory. This makes it possible to collect multiple TMR samples and quickly determine whether key nutritional components remain consistent throughout mixer discharge.
We recently evaluated this concept at Miner Institute. Lactating- and dry-cow TMR were prepared using either a deliberately short mixing time to create an inadequately mixed ration or a longer mixing time representing adequate mixing. The process was repeated over five days, with 10 samples collected at evenly spaced intervals during discharge. Samples were evaluated using both the PSPS and a portable NIR system. The results were encouraging. For the lactating-cow TMR, DM measured by portable NIR provided the clearest distinction between inadequate and adequate mixing. DM remained relatively consistent throughout discharge after adequate mixing, but changed substantially among sampling locations after short mixing. CP also provided useful information. For the dry-cow TMR, ADF was one of the strongest chemical indicators, while NDF, DM, starch, and CP also detected aspects of the imposed difference in mixing quality.
The comparison with the PSPS was particularly interesting. Several PSPS fractions responded to mixing quality, confirming the value of particle-size measurements. However, some PSPS fractions continued to vary throughout discharge even after adequate mixing. Our results therefore suggest that rapid chemical measurements can provide information about TMR uniformity that particle-size measurements alone may not capture.
These findings do not suggest that portable NIR should replace the PSPS. Rather, the technologies may be complementary: PSPS evaluates the physical distribution of the ration, whereas portable NIR provides an opportunity to evaluate its nutritional uniformity. Importantly, the best chemical indicator differed between diets, reinforcing that no single measurement is likely to characterize mixing quality under every feeding situation.
Portable NIR technology for this application is still relatively new, but the potential is promising. Its usefulness depends heavily on instrument performance and the quality of the calibration equations used to predict feed composition. As companies develop better instruments and larger, more robust calibration datasets, the accuracy and number of nutrients that can be reliably predicted should continue to improve. In the future, combining physical information from the PSPS with rapid chemical information from portable NIR could provide nutritionists with a much more complete assessment of whether the ration formulated on the computer is actually being delivered consistently to cows.
Stay tuned for the upcoming Cornell Nutrition Conference, where I will present the results of this new Miner Institute trial and discuss how portable NIR and conventional tools such as the PSPS can be used to improve the practical assessment of TMR mixing quality on dairy farms.
— Marcos Marcondes
