IS YOUR TMR REALLY WHAT YOU THINK IT IS? THE HIDDEN COST OF INACCURATE MIXER WAGON SCALES

The ration is formulated. You loaded the ingredients. You mixed the TMR. But did you actually feed the ration you intended to? Most farms routinely monitor feed ingredients, dry matters, and ration costs, but the scale responsible for weighing those ingredients may not be receiving similar attention. Mixer wagon scale accuracy is especially important for low-inclusion rate ingredients like premixes and feed additives. Even small deviations can become economically meaningful when multiplied across hundreds of cows and feeding days. Research performed on commercial dairies has demonstrated these deviations in ingredient weight occur daily, raising questions about how scale accuracy and consistency may affect the nutrition delivery to the bunk, and ultimately, herd performance.

In a study of five commercial dairies in the western United States, researchers evaluated shrink, weighing accuracy, and precision of mineral supplements within TMR. (Arce-Cordero et al., 2021; DOI: 10.1093/tas/txab087). Results found that the actual mineral supplement loading deviated from target by an average of 1.54%, while average mineral supplement shrink was 2.0%, due to storage and handling losses across the five farms. Although these percentages may appear small at first, repeated deviations from target ingredient weights can cause a compounding effect and carry the potential to contribute to the nutrient variation of a TMR’s composition.

So, why does a small weighing error matter? A 1.54% deviation may not sound like a lot, but it presents itself very differently when applied to a large forage ingredient vs a mineral or additive. A small, absolute error when weighing a large quantity of forage may have a relatively limited nutritive impact, while the same percentage of error in a premix or other concentrated ingredient can substantially alter what is delivered to your herd.

A scale does not have to be dramatically inaccurate to contribute to a larger feeding problem. A compound of what seems to be minor deviations in ingredient weights can quickly become part of a bigger picture that includes loading, mixing, sorting, and delivery variation. Recent research by Carroll et al. (2024; DOI: 10.3168/jdsc.2024-0564) evaluated feed delivery records from eight commercial dairy farms over a 52-week period and estimated the variation between formulated rations and what arrived at the bunks. The researchers demonstrated that these deviations commonly occur, with farms over feeding nutrients on 92% of days within a 28-day window. While deviations were not solely attributed to mixer wagon scale accuracy, the findings highlight the importance of monitoring not only what is supposed to be fed, but what is actually being delivered.

So, does an inaccurate scale automatically mean less milk? Not necessarily. These effects depend on the size, scale and persistence of the errors occurring, along with which ingredients are being affected, and ultimately how it is altering the nutrient composition that the cow is receiving. However, research has clearly shown that changes in dietary energy and metabolizable protein supply can influence milk yield and composition, thus affecting economic revenue for the farm. (Daniel et al., 2016; DOI:https://doi.org/10.1017/S1751731116001245). Maintaining accurate ingredient weights is just one piece of a much larger puzzle that ensures cows are receiving the nutrients they need to be successful.

These economic consequences of small changes in production can add up quickly. Consider a hypothetical 500 cow dairy. Let’s say each cow produces 1 lb less of milk per day, across 500 cows and 365 days that is a 1,825 hundredweight loss. The USDA announced the average price of Class IV milk for June 2026 was $20.96, multiplied by 1,825 hundredweight brings a $38,252.00 annual (hypothetical) loss. Now, this example is not intended to suggest any correlation between a 1-2% scale error causing a 1lb/day loss in production, but it is intended to illustrate that the small things matter. Furthermore, this does not account for the additional value of the feeds that are being “wasted” with inaccurate inclusion into the diet.

Accurate scales are a small but important piece of precision feeding. Regularly checking mixer wagon scales by using a known weight source and calibrating the scale when needed can help ensure the ration formulated is the ration delivered. For smaller feed additives, consider weighing them with a more accurate scale prior to adding them to the mix. These are all small, but impactful steps in protecting the value of every pound of feed being put into the wagon.

Of course, mixer wagon scale accuracy is only one potential source of variation between what’s formulated and what’s consumed. Changes in dry matters, ingredient shrink, loading techniques [and person(s)], mixing time, cow sorting and refusals can all attribute to nutritive differences. However, ensuring that the scale is accurately measuring what you’re putting in, is a relatively simplistic step in reducing variation of your TMR.

— Abby Allen

allen@whminer.com