Comparing Value of Feedstuffs

Once calculations have been made, producers can use the information to make appropriate decisions about which feedstuffs offer the lowest-cost rations that meet the animal’s requirements. This publication is meant to be a step-by-step guide to calculating feed values to allow appropriate comparison of feedstuffs.

For the purposes of this publication, we will focus on calculations of energy and protein in traditional feedstuffs fed to livestock. Energy will be discussed in the form of total digestible nutrients (TDN, which is one measure of energy concentration in a feed), whereas protein will be discussed in the form of crude protein (CP). Both measurements will be evaluated on a dry-matter (DM; 0% moisture) basis. Use of a DM basis is critical because removing moisture allows producers to compare nutrient concentrations of feeds with varying moisture content.

Before you can begin to talk about comparisons of feedstuff value, you must submit samples of feedstuffs to a reputable nutrition laboratory to determine the actual nutrient concentration of the sample. The lab results received are only as good as the samples submitted, so be sure to submit representative samples (for instructions about taking feed samples, see NDSU Extension publication AS1064, “Sampling Feed for Analysis,” www.ag.ndsu.edu/pubs/ansci/livestoc/as1064.pdf).

Examples of feedstuff nutrient profiles are listed in beef cattle and sheep National Research Council books and NDSU Extension publication AS1182, “Alternative Feeds for Ruminants,” www.ag.ndsu.edu/pubs/ansci/livestoc/as1182.pdf. However, nutrient concentration of forages and feed byproducts are quite variable and book values likely will not reflect the true value of the feeds on individual farms.

To calculate the amount of a feed you need to deliver to your livestock, you must convert the proportions in the feedstuff into pounds of nutrients contained in a certain weight of feedstuff (for this publication, we will use the unit weight of sale; that is, pounds or bushels as appropriate). Examples of calculating the amount of nutrients contained in different feedstuffs and their value per pound of TDN and CP are given in Table 1.

The focus of feed test results in this publication is the percent DM (column B), percent of TDN (column C) and percent of CP (column D). The unit of sale (column E) usually is defined as bushels or tons.

In the case of products being purchased on a bushel basis, knowing the bushel weight is important. For example, basing corn calculations on a test weight of 56 pounds per bushel will not be representative of lightweight corn purchased at 47 pounds/bushel. Similarly, comparing the cost of baled forages sold on a per-bale basis is very difficult if the bale weight is unknown or assumed.

While Table 1 contains all the information and calculations to determine what feedstuffs will provide the lowest-cost energy and protein, looking at the table in its entirety can be overwhelming.

In the next sections we will break down the calculation steps individually, show some examples and leave room for you to calculate the pounds of nutrients present in some of your feedstuffs.

Feeds can vary in moisture content. Although water is an essential nutrient, purchasing and transporting of water in feed can be costly. To calculate pounds of dry matter, multiply the pounds in each unit of sale (column F) by the percent of dry matter (column B). This calculation (Table 2) removes all moisture from the feed and allows you to compare high-moisture products (corn silage, wet distillers grains, etc.) and dry products (hay, dry cereal grains, etc.) appropriately.

The difference in pounds of dry matter in each ton of prairie hay and corn silage points out the dramatic impact that dry matter can have on how much your animals are eating. For every ton of prairie hay, dry feed amounts to 1,800 pounds, whereas for every ton of corn silage, dry product only amounts to 700 pounds.

In the case of very wet products, you may be offering large quantities of feed on an as fed-basis, but your animals may not be receiving the nutrients they need. For example, feeding 50 pounds of a 15 percent DM beet pulp would yield only 7.5 pounds of dry feed product.

Use Table 3 to calculate the pounds of dry matter in your feedstuffs.

Livestock do not require a certain amount of dry feed but rather require a certain amount of digestible feed. Similar to trucking water, purchasing and transporting indigestible feed can be costly. To calculate the pounds of TDN in each unit of sale, multiply the pounds of dry matter in each unit (column G) by the percent TDN in the feedstuff (column C). Calculations of pounds of TDN in each unit of sale are shown in Table 4.

In this example, alfalfa hay was added to the calculation table to illustrate the difference in pounds of TDN per ton, compared with prairie hay. The TDN values of the two respective feedstuffs result in a difference of nearly 200 pounds of TDN in each ton.

Moving to barley, 35.5 pounds of TDN are present in each 48 pound bushel. Similarly, 1 ton of barley would have resulted in 1,478 pounds of TDN, which is almost 1,000 pounds more than corn silage on an as-fed basis.

Use Table 5 to calculate the pounds of TDN in your feedstuffs.

Livestock also require a certain amount of protein to maintain productivity and rumen function. Protein is often one of the most expensive components of livestock feeding programs. To calculate the pounds of crude protein in each unit of sale, multiply the pounds of dry matter in each unit (column G) by the percent CP in the feedstuff (column D). Calculations of pounds of CP in each unit of sale are shown in Table 6.

For example, the high quality of the alfalfa hay is demonstrated by the amount of crude protein present in each ton, which is 3¼ times that of the prairie hay. We could have reached the same conclusion by simply looking at the percent of crude protein in each of the feedstuffs. However, the calculations are very important as we move to the next step of comparing the value of each feedstuff based on the purchase price or current value of the feedstuff.

Use Table 7 to calculate the pounds of CP in your feedstuffs.