A systematic review: methods to measure total mixed ration uniformity.

A uniform TMR ensures that the diet being delivered to the cows is consistent across time, both within a batch and across days. A systematic literature review was conducted to describe the different methods that have been utilized to measure within-batch TMR uniformity. Scientific papers that utilized methods to measure TMR uniformity were identified through a search in the Scopus database, which was conducted with no restrictions on the date of study publication or publication type. After filtering processes, 22 papers were selected for full review based on their relevance to within-batch TMR uniformity. Of the studies reviewed, 11 utilized particle size-based methods such as the Penn State Particle Separator (PSPS), 4 utilized tracer-based methods, 7 utilized nutrient analyses, 4 utilized near-infrared spectroscopy (NIRS), and 4 utilized image analysis or modeling techniques. Overall, there is no standardized or universally accepted method to assess TMR uniformity. Importantly, the methods identified should not be interpreted as equivalent, as each captures different aspects of uniformity, including physical structure, ingredient distribution, and chemical composition. Direct measurement methods, such as particle size and nutrient analysis, provide valuable information but are often labor-intensive and time-consuming. Indirect approaches, such as NIRS and image analysis, offer promising alternatives by reducing labor requirements and enabling faster or real-time assessments, although they still require further validation under practical feeding conditions. Therefore, future developments should focus on integrating physical, chemical, and optical indicators into cost-effective, automated tools capable of supporting routine monitoring of TMR uniformity in precision feeding systems.