Dairy Ration Software Models and Pre-Mixes an Overview

Dairy ration software today must address the use of approaches to determining nutrient requirements and supplies that attempt to accurately model the processes that produce the end product in the milk tank. Such an approach requires the inclusion of methodologies that address the dynamics of feed utilization at varying levels of intake and rates of passage. Within this context, premixes and mixed feeds represent an area of special consideration with respect to methodology.

The NRC 2001 model determines energy and protein values within the context of a complete diet. That context includes level of DMI and ration composition. Protein fractions and energy coefficients are therefore dynamic, changing as ration composition and other contextual inputs change.

In addition, to determine energy values the model utilizes multiple energy equations corresponding to the category of feed being evaluated. Therefore each feed must be assigned to a category in order to determine the equations used to calculate energy values. This approach works well when all ingredients are represented in the ration as individual items. However, when items assigned to different categories are combined in a mix the ability to distinguish individual ingredients with respect to their appropriate categories is lost. It is not possible to assign multiple categories to a mix.

No provision was made in the model for this scenario.

As a result, the practice of using the combined analysis of items bundled as a premix to "least cost the premix" outside of the context of a complete diet becomes somewhat problematic.

The current approach taken by Formulate2 steps outside the dynamic model to use the static energy coefficients provided.

Formulate2's nutrient list includes items for NEL (3x 2001), RUP(2001 Fxd) and RUP Digestibility (2001 Fxd). These nutrient items correspond to the 3x values listed in TABLE 15-1 (page 283 under column heading NEL 3X) and the RUP values in TABLE 15-2a (page 290 under the column heading showing DMI at 4.0% of body weight and ration forage content at 50% of DMI).

In addition, nutrient fields for NRC 1989 NE(l) and UIP/DIP values are provided. You may use either the NRC 2001 fixed coefficient fields or the NRC 1989 fixed coefficient fields for working with premixes outside the context of complete diets.

It should be noted however that the NRC 2001 static values were calculated with both the feed analyses and diet composition etc. stipulated for the tables. These static values DO NOT change as you update feed analyses. The only way to adjust these values is to substitute the feeds with new analyses into the stipulated diets used to determine the original values.

Because of this limitation, the NRC 1989 NE(l) values would seem a more viable option for "least costing" a premix formula. However, you must provide the 1989 NE(l) values for many feeds since inclusion of these values in feed records was limited to those feeds that directly corresponded with the international feed IDs of the NRC 2001 feed tables.

The illustration below describes how to place the analysis of a premix into a diet record in order to perform a linear least cost solution for the premix.

Creating a Premix

When a ration has been appropriately formulated, the Select Feeds form allows you to select the items you wish to include in a premix.

The combined "at intake" analysis of the selected feeds can then be copied to the feed clipboard.

Then imported into a separate ration record for used for "least costing" the premix.

The imported values can then be used as nutrient constraints for formulating the premix based on the imported analysis. The constrainable energy and protein items are the combined 3x values from the NRC 2001 publication tables or NRC 1989 values from laboratory analyses.

While this methodology provides an avenue for formulating a pre-mix outside the context of a complete ration, if the categories of premix ingredients use different energy equations, the pre-mix will not analyze within the ration context identically to the original individual ingredients when used as individual feed items. Additionally, it is not possible to accurately calculate a Kd value for a premix outside the context of a complete diet.

Once the premix solution has been obtained, in order perform accuate optimiztion, it must be detailed within an existing complete diet and its components reselected as a premix in order to accurately calculate it's B protein pool Kd value.

While all of this is possible, it is much simpler to confine the determination of premix indgredients to the context of a complete diet.

Strategies for successfully and accurately working around these issues when working within the context of complete diets have been devised and posted to this web site.

If premixes are created from the separates of a solved complete diet, assigning the Energy Source category to the premix produces the most conservative energy value and is a very workable approach. This allows Formulate2 to calculate a reasonably accurate Kd value for the premix and as a result, the premix will generally solve in the diet very similarly to its separates. However, a few adjustments are required when formulating the separates diet. For the details of the adjustments required click on the page link shown below.

Page Links

NRC 2001 Issues Related to Mixes How to successfuly and accurately work with mixes within the NRC 2001 theoretical framework

Online Tutorials:

• Optimizing with Mixes - How to successfully and accurately work with mixes withing the NRC 2001 Model. (this tutorial may be downloaded and saved for futrue use - has voice-over narration - requires active internet access 7.70 MB EXE)
• Working with Premixes - How to create pre-mixes from solved diet solutions. (this tutorial may be downloaded and saved for futrue use - has voice-over narration - requires active internet access 4.29 MB EXE)