Forage quality and its value

Edward K. Twidwell, Department of Agronomy and Kenneth N. Wegenhoft, Department of Agricultural Economics and Agribusiness; Louisiana State University Ag Center

The question of the value of different quality forages often arises in discussions with livestock producers. Often, stored forage (hay) supplemented with protein or grain is used in the winter feeding program and is a large part of the annual feed bill. Since feed cost is a majority of the cow-calf expense, proper feed cost management is important. The general concept is that “higher” quality forage is worth more than “lower” quality forage. Research indicates that animal production does increase with better nutrition. However, defining quality in hay and assigning values to hay quality is very often difficult.

Pricing
There are two concepts involved in pricing commodities:

•price determination

•price discovery

Price determination involves the interaction of supply and demand fundamentals which sets the general price level. Price discovery involves the interaction between the buyer and seller to arrive at an agreed upon sale price given the general price level set by the fundamentals. Quality, quantity, need, availability and bargaining ability are a few factors that influence buyers and sellers as they are setting their sale price.

Typically, hay markets for grass hay are influenced mostly by the local supply or demand situation with incomplete information about local conditions more the norm than not. Also, the feed value of hay is often not readily apparent based upon visual appraisal. And, the unit of measure in hay sales is typically the bale which can vary in size (square bales, small round bales and large round bales) and weight. As a result, often agreed-upon sale prices per bale do not reflect the value of the hay in terms of quality or weight.

Forage quality
Since forages are mainly used by livestock as a source of nutrition, forage quality is defined as an expression of the characteristics that affect consumption, nutritive value and the resulting animal performance.

Factors influencing forage quality
Since many factors affect forage quality, no single factor can be used to make this prediction. Maturity stage at harvest, forage species and variety, leafiness, harvest and storage conditions and the presence of pests are important factors that determine quality.

•Maturity
This refers to the growth stage of a plant at the time that it is harvested. As forage plants mature, the amount of structural fiber and lignin increases. While the structural fiber components can be partially digested by livestock, lignin is not digestible. As the amount of structural fiber and lignin increases, digestibility of the forage and the consumption of the forage by livestock decreases.

•Species and variety
Forage quality differences between species and among varieties within a species are generally related to differences in fiber content, leafiness or the presence of undesirable components (i.e. mold) which negatively impacts forage digestibility and livestock consumption.

•Leafiness
Leaves contain more digestible nutrients and protein than stems. When forage plants mature, the leaf-to-stem ratio decreases. Thus, forages with a greater amount of leaves are more likely to be of higher quality.

•Harvest and storage conditions
Forage crops decrease in the amount of digestible nutrients during the curing process because of plant respiration. Decreases in digestibility can also occur from the leaching of soluble nutrients during rainfall and the physical loss of leaves at harvest. If hay with excessive moisture is packaged and stored, mold may develop. Mold-producing organisms generate heat through respiration; the mold and heat reduce consumption as well as protein and digestibility.

•Presence of pests
The presence of some diseases, insects and weeds have been responsible for reduced forage quality. Particularly noteworthy pests are leaf diseases and high populations of fall armyworms.

Forage testing
Forage testing is used to determine nutrient composition and potential animal performance. Once the factors that determine forage quality have been measured, a more accurate ration can be formulated for a specific class of livestock according to nutritional requirements for optimum performance. Forage testing is used to indicate nutrient content of hay, silage or any other forage fed to livestock. Depending on the livestock class being fed, nutrient content of the forage may be adequate or inadequate for maintenance and production. Because hay is used as part of a feeding program, the price or value of the hay should in part reflect the nutrient value.

Methods of forage testing
Several methods of estimating or analytically determining nutrient content of forages have been used for many years. Recently, new forage testing procedures have been developed. Some methods for determining forage quality include visual appraisal, chemical analysis and near infrared reflectance spectroscopy (NIRS). Each method has strong and weak points as well as specific uses in forage evaluation.

•Visual appraisal
Visual appraisal is the oldest and most widely used forage evaluation method. The term “visual appraisal” is not limited to the sense of sight; it is also based on texture and odor. Forage appearance is evaluated by color, leafiness, maturity and the presence of foreign material (mold, dust and weeds). Since visual appraisal relies heavily on subjective evaluation, it is possible that no two people will evaluate the same forage in the same way. Even though visual appraisal is relatively fast, factors such as color and odor do not necessarily relate well to animal performance.

•Chemical analysis
A meaningful assessment of forage quality requires an evaluation of its chemical makeup. Determination of the chemical components requires laboratory procedures. The chemical analysis of a forage will identify nutritionally strong and weak points. The main limitation of this method is slow turnaround time and expense.

•NIRS
This is a computerized method of forage testing. It is based on laboratory chemical analysis procedures and greatly reduces the sample turnaround time. The forage can be analyzed in less than 10 minutes using NIRS, compared to hours and even days for conventional chemical methods. The accuracy of NIRS depends upon the accuracy of the chemical analyses used to calibrate the instrument.

Obtaining a representative forage sample
A forage analysis is only as good as the sample submitted. Poor sampling can result in misleading values and less-than-expected animal performance. One forage sample should be sent to the laboratory for each lot of forage. The term “lot” refers to a specific quantity of similar forage.

•Conventional square bales
A bale probe should be used to collect samples. The probe should be about 12 to 18 inches long, hollow and at least 3/8-inch in diameter. Most probes are designed to attach to an electric drill or brace. Sample at least 20 average bales from each lot. Take one core from the end of each bale. Place the forage from core samples in a clean plastic bucket and mix well. Put about 1 quart of forage material in a zippered plastic bag for analysis.

•Large round bales
Sample 10 bales from each lot. Take two samples from the sides (not the ends) of each bale, and mix the forage thoroughly in a plastic bucket. Remove about 1 quart for analysis.

Definitions of common forage analysis terms

•Dry matter (DM)
This is the percentage of forage that is not water. Water does not add protein or energy to the diet, so forage nutrient values must be compared on a dry matter basis.

•Crude protein (CP)
This is a measure of the amount of nitrogen (N) in a forage. Crude protein is calculated by multiplying the total N content by a constant, 6.25. This is based on the assumption that proteins contain about 16 percent N. It includes both true protein and non-protein N and does not make a distinction between available or unavailable protein.

•Neutral detergent fiber (NDF)
Neutral detergent fiber is a measure of total structural carbohydrate in the plant. The NDF fraction is partially digestible. As such, NDF is considered an indicator of forage bulkiness and is related to dry matter intake. Lower NDF indicates more forage intake potential.

•Acid detergent fiber (ADF)
Acid detergent fiber is a measure of the least digestible plant carbohydrate (cellulose and lignin). It is negatively correlated with digestibility and consequently is often used to estimate energy content of forages. Lower ADF indicates higher digestibility.

•Total digestible nutrients (TDN)
This is an estimate of all digestible organic nutrients (protein, carbohydrates and fat) of a forage that are available to the animal. TDN is normally calculated from ADF analysis.

•Relative feed value (RFV)
This is an index used to rank forages based on estimated digestibility (ADF) and intake potential (NDF) of a forage. RFV attempts to measure the overall feed value of a forage using a single number. RFV is not measured in percentage but is simply used to compare quality of various forages. RFV was developed for alfalfa, but it can also be used to rank the quality of various grasses and legumes.

Hay storage considerations
In research trials in which large round bales have been stored outside without protection for six months or more, dry matter losses of 30 percent or greater have been common. If hay is to be stored outside, it is desirable to locate the storage site close to the feeding area because bales become more difficult to handle as they weather.

There are numerous types of commercially available coverings for large round hay bales, and they vary in both effectiveness and cost. The use of these coverings have been demonstrated to dramatically reduce hay storage losses as compared to storing hay outside with no protection. Protecting the bottoms of the hay bales is also important as moisture can easily be drawn up into the bales. Any type of material such as wooden pallets, railroad ties and crushed rock can be used to prevent direct contact between the hay bales and the soil.

Barn storage is usually considered to be a highly effective and consistent method of storing hay. Most research studies demonstrate that dry matter losses of only 0 to 5 percent occur when hay is stored in a barn.

Hay feeding considerations
It is not uncommon for hay feeding losses to be as high as storage losses (greater than 30 percent), especially if hay is fed outside. Feeding losses include trampling, leaf shatter, chemical and physical deterioration, fecal contamination and refusal. When hay is fed outside on the ground, the amount of hay wasted will be much less when only a one-day hay supply is given as compared to two- or four-day supplies. Unrestricted animal access to large round bales of hay can result in excessive amounts of feeding waste. It is highly advantageous to place a barrier between the hay and the animals. The barrier can be an electric wire, feeding racks or rings.

Value of hay
The value of hay is difficult to determine because of the lack of measurable standards related to the many different quality factors, storage methods, production techniques, levels of nutrients and end uses. In addition, information on supply and demand fundamentals is poor or non-existent.

One method of pricing hay would be to use an “average price” for an “average quality” hay to represent the base price. Adjustments to the average price could be based on the amount of crude protein (CP) contained in the hay. In this way, hay with a higher CP content would have a higher value per ton than hay with average CP content. Likewise, hay with a lower CP content would have a lower value. The value of CP hay could be based on the value of CP in other feedstuffs.

This method requires that the weight and crude protein content of hay be known so that a difference in value can be calculated. Also, this method does not take into consideration TDN or other quality components of hay that have value.

Higher quality hay does have a higher value because of its effect on animal performance. The buyer or seller of hay that knows the weight and crude protein content of the hay they are handling can use this method to arrive at the value of hay better (or worse) than average. HG

References omitted but are available upon request at editor@progressivedairy.com

—Excerpts from Louisiana State University Extension website