Hay quality is important. Yet many producers rarely test their forages for digestibility, moisture and other measures of quality such as protein, vitamin and mineral content. If you plan on growing your own forage crop, either to use personally, sell outright, or if you are buying forages, knowing its nutritional value is key in balancing livestock rations and getting a fix on its dollar value.
The measurements found on a forage report are like the nutritional data on the side of your Wheaties cereal box. You would not feed the “breakfast of champions” to your children without first acknowledging the ingredients were indeed of champion quality. Almost everything you need to know in maintaining healthy livestock or a first-class rate of gain comes in the form of a forage analysis report.
Crude Protein
We begin the report breakdown with crude protein, one of the most understood nutritional measurements. Proteins are composed of 22 amino acids, which are crucial for tissue growth and body function. Some of these proteins are supplied in the body and are referred to as non-essential amino acids. Those which cannot be produced in the body are essential amino acids and thus must be supplied in feeds. Feeds in the form of forages can be expensive, so obtaining forage that meets your livestock’s protein needs is very important for growth and maintenance. To determine CP, laboratories measure the nitrogen (N) content, and use the calculation percent N x 6.25 = CP. Forages high in CP are budded alfalfa (22-26 percent), early flower red clover (14-16 percent), and early harvest tall fescue (13-16 percent), while those low in CP are eight week old Bermuda grass (6-8 percent), and mature switchgrass (6-10 percent).
Acid Detergent Fiber
Acid detergent fiber (ADF) is currently the most widely used system for analyzing forages. This system identifies how much of a forage is not digestible. As plants mature they tend to increase in a component called lignin that adds strength and rigidity, which is good for the plant but not good for digestibility. Measures of ADF are inversely related to digestibility of a forage. For example, the higher the ADF, the lower the digestibility. In other words, the more mature a plant is, the less the animal will be able to digest.
Neutral Detergent Fiber
While ADF is the measure of tougher cell wall components, neutral detergent fiber (NDF) is the measure of all the cell wall components, some of which are digestible. The NDF value is found by using a fraction of the ADF value plus hemicellulose, a carbohydrate that decomposes when it reacts with water, more readily to a simple sugar than cellulose. An important determinant of dry matter intake (DMI) by the animal, NDF values are much the same as ADF values in that as they increase, DMI will decrease. In general, ADF values in forages can range from 3 percent in corn grain to 40 percent in mature forages and 50 percent in straws. NDF values can range from 10 percent in corn grain to about 80 percent in straws and tropical grasses, which demonstrates why many beef producers choose to present a higher digestible feed such as corn grain to their livestock).
Dry Matter
A similarly important measurement to understand is a forage’s dry matter (DM). Dry matter is the percentage of forage that is not water. This measure is ideal for comparing forages, as it is the best indicator of nutrients since most animals tend to eat on a dry matter basis. Cattle in particular require a set amount of DM, so as forages take on more water, cattle are required to consume more forage to meet their DM requirement. Most reports will give a DM value as well as an “as-received” or wet basis value. Since the DM measurement does not contain water, its values for nutrient content will tend to be higher than the “as received” value since water tends to dilute other nutrient contents.
Ash
The last main measurement which should always be addressed on a forage analysis report is ash. Ash is the total mineral content within a forage sample. Calcium (Ca) and phosphorous (P) are determined in all manner of tests, but analyses may also include potassium (K), magnesium (Mg), or any other requested mineral if a Near Infrared Reflectance Spectroscopy (NIRS) test is used. Calcium and phosphorous make up about 70 percent of the total mineral content within the body, and about 30-50 percent of the minerals in milk. Although a much higher majority of that resides in the bones and teeth, Ca and P play important roles in other body functions as well. Ca and P work hand in hand, a constant Ca:P ratio of 1.5:1 to 2:1 must be maintained for most livestock species. For example, certain legumes like clovers and alfalfa are often higher in Ca, and supplemental P must be added.
Other minerals occasionally measured are potassium (K) and magnesium (Mg). Potassium is usually not harmful in high levels, since excesses are easily excreted in urine, assuming adequate water is present. Deficiencies, however, could lead to sluggishness and a reduced feed and water intake. Magnesium deficiency can be exceptionally devastating during the spring when young, growing grasses are most succulent, but may also be a concern in the fall when new growth of cool season grasses or wheat pastures occurs. This disorder, most commonly referred to as grass tetany, can be caused by low levels of Mg and/or high levels of K which can tie up available dietary Mg. Grass tetany may also be addressed as grass staggers or wheat pasture poisoning.
This article was written in conjuction with Missouri State University's Feeds and Feeding course. Review the list of references for this article on our website at www.ozarksfn.com.
