Forage Quality & Testing

Learn more about the importance of testing for forage quality.
Forage Quality & Testing - Articles

Updated: August 8, 2017

In This Article
Forage Quality & Testing

Learn about the importance of physical appraisal and chemical analysis in determining forage quality.

Plant composition

All forage plants are composed of cells having fibrous cell walls for support and protection. Contained within the cells are several soluble compounds, most of which are highly digestible (Fig. 1). Since cell wall material is the primary constituent of forages, one of the main objectives of forage analysis is to characterize the cell wall fiber.

Plant fiber has three major components: cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are digestible to some extent by ruminants. Ruminants can convert these fiber components to energy because the rumen provides the correct environment for bacteria and other microorganisms that actually break down the fiber. Lignin is indigestible, and thus cannot be used by ruminants for energy.

Plant morphology

Both grasses and legumes have two main plant parts, leaf and stem. As a structural component of the plant, stems typically contain more fiber for support. Leaves, on the other hand, provide a means for capture and utilization of energy from sunlight and tend to be lower in fiber content than stems. Given the large difference between the digestible fiber of stems and leaves, the proportion of leaf to stem in a given forage plant relates directly to its forage quality.

Physical appraisal

Appraisal of a forage based on sight, smell, and touch can provide some general information, but chemical analyses are needed to asses the economic potential of the forage.

At a recent forage meeting, approximately 80 forage producers and industry people were asked to rank four bales of hay by a visual appraisal of their forage quality. The hay ranged from pure alfalfa to an alfalfa-grass mix. An objective quality evaluation of the same bales, based on Relative Feed Value (RFV), found considerable differences among them. There was no consistent pattern in the ratings by individuals but, in fact, the bale judged best on the basis of appearance had the lowest RFV of the four. Clearly, objective forage analysis is required.

Chemical analysis

The Van Soest Fiber Analysis System separates feeds into distinct fractions that relate to their nutritive value. Neutral detergent fiber (NDF) consists of the total fiber in the forage and relates negatively to forage intake by ruminants. Acid detergent fiber (ADF) is composed of highly indigestible fiber and relates negatively to forage digestibility. Total nitrogen concentration in the forage (usually expressed as crude protein) is also a useful measure, since adequate intake of nitrogen is essential for animal productivity.

Forage laboratories analyze samples for NDF, ADF, and total nitrogen. It is also possible to accurately estimate these components using near infrared reflectance spectroscopy (NIRS). Other estimates of forage quality, such as total digestible nutrients (TDN), net energy of lactation (NEL), and relative feed value (RFV) are derived from mathematical manipulations of NDF and ADF values.

Greater net profit is the bottom line for why livestock producers need to know the quality of the forages they are feeding!

For nearly four decades scientists have been refining their ability to test forage quality. This has been done in an effort to improve animal nutrition and consequently animal production. Analytical procedures that previously required a week, or more, to complete can now be done in less than 10 minutes and with more accuracy than before. As the ability to analyze forages has improved, the understanding of how to use the test results to improve animal efficiency and performance has also improved. Unfortunately though, forage quality testing is a valuable management tool that many livestock producers still do not utilize.

Greater net profit is the bottom line for why livestock producers need to know the quality of the forages they are feeding! Not knowing the exact quality of the forage being fed is a two-edged sword that can cut into profits either way it swings. A dairy producer who guesses that the crude protein (CP) content of the haylage is 2% units lower and corn silage is 1% unit lower will be feeding more supplemental protein than is necessary. This extra CP to the ration will add $0.09/cow/day in feed costs. With a herd of 100 cows, this is equivalent to $9.00/day. It would take just a little over 3 days of not knowing the quality of the forages and feeding extra protein, as in this example, to pay for the cost of quality analyses (forage quality testing usually costs less than $15.00/sample).

The other edge of this two-edged sword of not knowing forage quality, is over estimating forage quality. Guessing that forage crude protein is greater than what it actually is resultes in adding insufficient supplemental protein to the ration and saving feed costs. Unfortunately, the cows are being "short changed" on CP which could have a negative impact on milk production, especially in early lactation.

It is also important to note that guessing at fiber and mineral content will also have enormous economical impact. For example, the neutral detergent fiber (NDF) content of forages helps determine how much of the forage an animal will consume. Guessing too high or too low can have tremendous implication on intake, animal performance, and health. Knowing the quality of the forage being fed to animals not only saves or makes more money it also allows managers to provide better animal nutrition which will result in greater animal production and improved animal efficiency (lb milk or weight gain per pound of feed consumed).

Knowing the quality of forages when selling or buying them has also proven to be economically smart. At Pennsylvania hay auctions, where the quality of the hay is analyzed, and the results posted on each load prior to the auction confirms the economic value of knowing hay quality. At these auctions, each percentage unit increase in crude protein resulted in $8.00 more per ton. Selling 10 ton of 20% CP hay as 18% CP hay because the quality was not tested will cost the seller about $160! On the other hand, buying 10 ton 18% CP hay as 20% CP hay cost the buyer $160! A similar relationship between quality and price did not occur at hay auctions when the quality of the hay was unknown. Establishing a "fair" price for hay, if you are buying or selling, involves both parties knowing the quality of the hay.

Collecting a sample to be submitted for quality analysis is the first step in obtaining accurate and useful results.

Quality results will be useful only if the sample represents what the animals will eat. Therefore, take a good random sample from each lot (forage taken from the same cutting at the same stage of maturity, the same forage species and variety, from the same field at the same time). Remember that the small sample collected may represent several tons of forage. Note the location of each lot in the barn or silo for easy reference when feeding.

Collecting Samples of Baled Hay

  1. Take a separate sample from each field and cutting.
  2. Always sample with a bale corer such as a Penn State Forage Sampler. It is impossible to get a representative sample by using bale slices!
  3. Insert the sampler to full depth into the end of each bale sampled. This will insure getting an accurate sample
  4. Take at least 20 widely separated sample cores from each lot.
  5. Mix the 20 cores in a clean pail and place in a tight, clean, plastic bag.
  6. Label each bag clearly with your name, address, the sample number, forage mixture, stage of maturity, and date harvested.

Collecting Samples of Haylage and Silage at Harvest

  1. Take sample as the silage is placed in the silo. Silos with excessive seepage should be resampled upon feeding.
  2. Collect three to five handfuls of haylage or silage from the first load of the day in a plastic bag and place in refrigerator or freezer immediately.
  3. Follow the same procedure for several loads of forage throughout the day. Combine samples and mix well to obtain a representative sample.
  4. Repeat for each field if more than one field is harvested in any one day.
  5. Throw different colored styrofoam egg cartons into the blower at the end of each lot. This, will aid you in identifying the lots later as the feed is unloaded.
  6. Label the bag clearly with your name, address, the sample number, forage mixture, stage of maturity, and date harvested.

Collecting Samples of Haylage and Silage from Storage

  1. Collect a one to two pound sample from the silo as it is discharged from the unloader.
  2. Do not collect the samples from the spoiled material on top of the silo. In upright silos, wait until two to three feet of silage has been removed.
  3. Collect samples from the morning and evening feedings over a two day period.
  4. Mix the samples thoroughly, place in a clean plastic bag, and seal.
  5. Store immediately in a cold place, preferably in a freezer, until analyzed.
  6. Label the bag clearly with your name, address, the sample number, forage mixture, stage of maturity, and date harvested.

Preparing and storing collected samples

Hay samples should be kept in a cool place while haylage and silage samples should be kept frozen in an airtight container until sent and then should be mailed in insulated bags - preferably early in the week - to prevent bacterial decay which might change the results. Remember that the results will only be as good as the sample taken. Follow the above steps to collect a representative sample for quality analysis.

Once you have gone to the effort of correctly collecting a sample, how can you be sure that the results you receive from the testing laboratory are accurate?

Frequently, concerns about laboratory testing focus on the methods used in determining forage quality. However, the focus of concern should be on the accuracy of results and not the technique of obtaining the results. To help you determine if the test results are accurate or not, we have outlined below some questions to ask the laboratory manager.

  1. Is the lab certified or does it participate in a check-sample program (also called proficiency testing program)? The National Forage Testing Association (NFTA) certification program monitors the performance of a lab against other labs to alert them of potential problems in their accuracy. The American Association of Feed Control Officials conduct a check-sample program that insures consistently and accuracy amoung participating labs. Involvement in either of these programs indicates that the laboratory is concerned with the accuracy of its results.
  2. Does the lab include duplicate samples or quality control check samples in each group of samples analyzed? One of the easiest ways for a laboratory to monitor results is by analyzing replicates of a sample. If the analyses for replicates are not similar, then there is a problem in the testing procedure. In addition, the inclusion of standards or check samples (material of known quality) in each group of samples analyzed can indicate if the analytical procedure is working correctly or not. Standards or check samples can also alert the laboratory technician of small changes in results over time and allow corrective steps to be taken.
  3. What analytical methods are used by the laboratory? There is more than one method of analyses for most plant constituents. Laboratories should be using methods of analysis which are well validated and approved by the Association of Official Agricultural Chemists (AOAC).
  4. Laboratories which use NIRS can be asked three additional questions that will help determine if the results are accurate. Like other laboratory methods, NIRS analysis is sophisticated and should be conducted and monitored by trained personnel.
  5. How frequently are the NIRS instrument and the calibration equations monitored? NIRS instruments should be monitored by running a check sample daily or after every 25th sample, whichever is more frequent. Calibration equations should be monitored by conducting laboratory analyses on every 25th sample. Again, this additional monitoring adds additional costs which will increase the fee charged for each sample.
  6. Does the laboratory do chemical analysis in addition to NIRS? NIRS methods are based on calibrations derived from chemical methods. NIRS labs which have no chemical analytical capability have no method within their lab to monitor the reliability of their calibration equations. It is not impossible for a NIRS-only lab to have a good monitoring program. But it is much more difficult since all of the monitoring samples would have to be sent to another lab for chemical analysis.
  7. How does the lab identify and analyze inappropriate samples received for NIRS analysis? Each NIRS calibration is specific for a particular type of sample. For example, corn silage is most accurately analyzed with a calibration equation developed for corn silage and not a calibration equation developed for alfalfa haylage. How does the lab identify samples that are inappropriate for the calibration equation and then does it have a protocol for analyzing these samples?

Keep in mind that laboratory monitoring practices increase the cost of the analysis. Asking these 6 questions will help evaluate a laboratory and is one way to become more knowledgeable about purchasing analytical services. Laboratories generally report results of analyses as a single number. This does not mean that hay which tested at 20% CP is exactly 20.0% CP. Instead, it means that the hay is 20.0% crude protein plus or minus some variation. The amount of this variation will differ from lab to lab and from method to method. A variation of about 3% can be expected between labs for measurements of crude protein. In other words, a hay sample which tested 20% CP at one lab would be expected to test anywhere from 19.4 to 20.6% CP at another lab or at the same lab if the analysis was repeated. Variation is usually much higher for fiber measurements than for crude protein measurements.

Objective forage analysis is required to determine the quality of a forage.

What is Forage Quality?

Fluctuations in milk prices, feed costs, and government programs are forcing dairy farmers to become more efficient with their farm operation. Since feed accounts for approximately one-half of the total cost of producing milk, and high quality forage optimizes the productivity of the animals, increasing the quality of forage available is one of the best methods of improving overall feeding efficiency. To effectively produce high quality forage, it is necessary to understand what forage quality is and to keep the factors influencing forage quality in perspective.

Forage quality is defined as the sum total of the plant constituents that influence an animal's use of the feed. Along with its quality, the overall potential feeding value of a forage feed is influenced by the form in which it is fed (e.g., particle size), the palatability of the forage, and by the quality of other feeds in the ration (associative feed effects).

What is quality forage worth?

The value of high quality forage in a balanced ration is evident in Table 3. When three hays of low, medium, and high quality, along with corn silage and a mixed feed grain are used to balance a ration, total feed cost for the high quality hay ratio is $0.11 less per cow per day than the medium quality hay ration. Income over grain cost is $0.45 more per cow per day for the high quality hay ration than for the medium-quality hay. For 100 cows over a year, this difference is greater than $16,000. Low quality hay does not allow an animal to consume enough digestible energy to be highly productive.

What Determines Forage Quality?

Plant composition

All forage plants are composed of cells having fibrous cell walls for support and protection. Contained within the cells are several soluble compounds, most of which are highly digestible (Fig. 1). Since cell wall material is the primary constituent of forages, one of the main objectives of forage analysis is to characterize the cell wall fiber.

Plant fiber has three major components: cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are digestible to some extent by ruminants. Ruminants can convert these fiber components to energy because the rumen provides the correct environment for bacteria and other microorganisms that actually break down the fiber. Lignin is indigestible, and thus cannot be used by ruminants for energy.

Plant morphology

Both grasses and legumes have two main plant parts, leaf and stem. As a structural component of the plant, stems typically contain more fiber for support. Leaves, on the other hand, provide a means for capture and utilization of energy from sunlight and tend to be lower in fiber content than stems. Given the large difference between the digestible fiber of stems and leaves, the proportion of leaf to stem in a given forage plant relates directly to its forage quality.

Physical appraisal

Appraisal of a forage based on sight, smell, and touch can provide some general information, but chemical analyses are needed to asses the economic potential of the forage.

At a recent forage meeting, approximately 80 forage producers and industry people were asked to rank four bales of hay by a visual appraisal of their forage quality. The hay ranged from pure alfalfa to an alfalfa-grass mix. An objective quality evaluation of the same bales, based on Relative Feed Value (RFV), found considerable differences among them. There was no consistent pattern in the ratings by individuals but, in fact, the bale judged best on the basis of appearance had the lowest RFV of the four. Clearly, objective forage analysis is required.

Chemical analysis

The Van Soest Fiber Analysis System separates feeds into distinct fractions that relate to their nutritive value. Neutral detergent fiber (NDF) consists of the total fiber in the forage and relates negatively to forage intake by ruminants. Acid detergent fiber (ADF) is composed of highly indigestible fiber and relates negatively to forage digestibility. Total nitrogen concentration in the forage (usually expressed as crude protein) is also a useful measure, since adequate intake of nitrogen is essential for animal productivity.

Forage laboratories analyze samples for NDF, ADF, and total nitrogen. It is also possible to accurately estimate these components using near infrared reflectance spectroscopy (NIRS). Other estimates of forage quality, such as total digestible nutrients (TDN), net energy of lactation (NEL), and relative feed value (RFV) are derived from mathematical manipulations of NDF and ADF values.

Ranking of Major Factors that Influence Forage Quality

Six major factors affecting forage quality (not yield), ranked by their impact on forage quality, include: 1) maturity, 2) crop species, 3) harvest and storage, 4) environment, 5) soil fertility, and 6) variety. The relative importance of each of these factors, along with some exceptions to the ranking, are described below.

  1. Maturity (harvest date). Maturity is the most important factor affecting forage quality. Forage quality is never static; plants continually change in forage quality as they mature. As plant cell wall content increases, indigestible lignin accumulates. In fact, forage plant maturity changes so rapidly that it is possible to measure significant declines in forage quality every two or three days.
  2. Crop species. Differences in forage quality between grasses and legumes can be very large. The protein content of legumes is typically much higher than that of grasses, and legume fiber tends to digest faster than grass fiber, allowing the ruminant to eat more of the legume.
  3. Harvest and storage. Improper harvest techniques can seriously reduce forage quality, primarily through the loss of leaves. Storing a hay crop at an incorrect moisture content, or improper ensiling of a forage crop, can dramatically lower its quality.
  4. Environment (climate). Moisture, temperature, and the amount of sunlight influence forage quality. Rain damage is very destructive to forage quality. When bad weather delays harvesting, the forage crop becomes more mature and hence lower in quality. High temperatures may increase lignin accumulation and decrease quality, but drought stress may actually benefit quality by delaying maturity.
  5. Soil fertility. Soil fertility affects forage yield much more than it does quality. While it is possible to produce high quality forage on poor, unproductive soils, it is generally very difficult to produce high yields of high quality forage with an unproductive soil resource. Proper soil phosphorus (P) and potassium (K) levels help to keep desirable legumes in a mixed seeding and also reduce weed problems. It is necessary to balance soil fertility to avoid mineral imbalances in ruminants. Low soil fertility, as well as very high fertility, has resulted in reduced forage quality.
  6. Variety (cultivar). After decades of breeding foraged for yield and persistence, attention has recently been focused on developing or identifying varieties with improved quality. Variety or cultivar can affect forage quality, but not as greatly as the other five factors. In alfalfa, selection for improved quality is underway by most commercial companies, and several U.S. firms have initiated selection in corn silage hybrids for improved forage quality.

Other factors affecting forage quality. Several lesser factors also can influence forage quality. Weeds can negatively affect quality, especially in the case of noxious weeds. Insect pests can lower forage quality, particularly if they cause significant leaf loss. Plant diseases can affect quality when they result in a shift in the species present in the field and when they promote leaf senescence. Insects and diseases generally have their greatest impact on yield and persistence of forages.

Exceptions to the ranking

Forage crops that accumulate a significant quantity of grain may increase slightly in overall quality with maturity as grain content increases in the plant. Some species contain antiquality factors that can lower animal performance. Variety can become the most important forage quality factor in cases where varieties are developed to significantly reduce or eliminate species antiquality factors, as in low-alkaloid varieties of reed canarygrass. Harvest and storage of a forage crop at a moisture content leading to spontaneous combustion would plainly become a most important factor. Or, if prolonged flooding or drought threatens a forage crop, environment becomes as important as any of the other factors. Certain soil fertility conditions, such as a very low pH, could eliminate alfalfa from a mixed seeding, thereby changing the species composition of the stand and greatly diminishing its quality.

Significance of Factors that Influence Forage Quality

All of the ranked factors above can be controlled to some extent through proper management. For example, maturity can be controlled by adjusting harvest dates. The highest quality species that fit the available soil resources should be chosen. Drying agents and preservations may help to avoid rain-damaged forage. Soil testing can identify optimum lime and fertilizer additions. Although variety selection is very important for yield and persistence, it is of relatively less value to forage quality.

Attempts being made to modify alfalfa plant composition and leaf-to-stem ratio through breeding, as with the multileaf alfalfas, using chemical analyses as the selection criteria. Several alfalfa trials throughout the United States now include forage quality in their evaluation of new varieties. At a given trial site, all varieties are harvested on the same date and then evaluated for forage quality. Any differences in maturity among varieties could influence the ranking of those varieties. In other words, some of the reported differences in forage quality between varieties may only be reflecting that they were harvested and compared at different maturities. Keep in mind that maturity is the most important factor influencing forage quality.

Selection for forage quality in corn silage is now being done, and it is likely that many commercial companies will be promoting hybrids on this basis as well. Preliminary studies at Cornell University, Michigan State University, and the University of Idaho indicate that there is a range in overall silage quality among hybrids. It may be possible to breed for higher stover quality while maintaining a high grain-stover ratio, and develop a silage hybrid with overall higher digestibility. As with alfalfa, selection may be based on chemical in vitro analyses, with little or no actual animal performance data to back up forage quality claims. This means that varieties ultimately will be compared for animal performance on the farm by the forage producer. Claims of improved forage quality may be added only after those varieties excel in animal performance tests.

Keeping quality in perspective If you want to produce high quality forage, keep in mind the ranking of quality factors and their relative contribution to quality. While all six factors described are important, using high quality varieties will be advantageous only when the other five factors are operant. Quantity (yield) of forage is also a major consideration. Evaluate your total forage requirements, and then select the crop and the appropriate acreage of that crop that best meet the needs of the group or groups of animals to be fed. It ultimately comes down to economics; high quality forage can help keep farmers in the dairy business.

Fluctuations in milk prices, feed costs, and government programs are forcing dairy farmers to become more efficient with their farm operation.

Since feed accounts for approximately one-half of the total cost of producing milk, and high quality forage optimizes the productivity of the animals, increasing the quality of forage available is one of the best methods of improving overall feeding efficiency. To effectively produce high quality forage, it is necessary to understand what forage quality is and to keep the factors influencing forage quality in perspective.

What is Forage Quality?

Forage quality is defined as the sum total of the plant constituents that influence an animal's use of the feed. Along with its quality, the overall potential feeding value of a forage feed is influenced by the form in which it is fed (e.g., particle size), the palatability of the forage, and by the quality of other feeds in the ration (associative feed effects).

Major factors that influence quality

Six major factors affecting forage quality (not yield), ranked by their impact on forage quality, include: maturity, crop species, harvest and storage, environment, soil fertility, and variety. The relative importance of these factors, and some exceptions to the ranking, are described as follows.

Figure 1. Maturation of plant cell walls.

  1. Maturity (harvest date). Maturity is the most important factor affecting forage quality. Forage quality is never static; plants continually change in forage quality as they mature (Figure 1). As plant cell wall content increases, indigestible lignin accumulates. In fact, forage plant maturity changes so rapidly that it is possible to measure significant declines in forage quality every two or three days.
  2. Crop species. Differences in forage quality between grasses and legumes can be very large. The protein content of legumes is typically much higher than that of grasses, and legume fiber tends to digest faster than grass fiber, allowing the ruminant to eat more of the legume.
  3. Harvest and storage. Improper harvest techniques can seriously reduce forage quality, primarily through the loss of leaves. Storing a hay crop at an incorrect moisture content, or improper ensiling of a forage crop, can dramatically lower its quality. Estimated average economic losses during harvest and storage are shown in Figure 2.
  4. Environment (climate). Moisture, temperature, and the amount of sunlight influence forage quality. Rain damage is very destructive to forage quality. When bad weather delays harvesting, the forage crop becomes more mature and hence lower in quality. High temperatures may increase lignin accumulation and decrease quality, but drought stress may actually benefit quality by delaying maturity.
  5. Soil fertility. Soil fertility affects forage yield much more than it does quality. While it is possible to produce high quality forage on poor, unproductive soils, it is generally very difficult to produce high yields of high quality forage with an unproductive soil resource. Proper soil phosphorus (P) and potassium (K) levels help to keep desirable legumes in a mixed seeding and also reduce weed problems. It is necessary to balance soil fertility to avoid mineral imbalances in ruminants. Low soil fertility, as well as very high fertility, has resulted in reduced forage quality.
  6. Variety (cultivar). After decades of breeding forages for yield and persistence, attention has recently been focused on developing or identifying varieties with improved quality. Variety or cultivar can affect forage quality, but not as greatly as the other five factors. In alfalfa, selection for improved quality is underway by most commercial companies, and several U.S. firms have initiated selection in corn silage hybrids for improved forage quality.

Figure 2. Economic value of harvest and storage losses of alfalfa. (Adapted from D. R. Buckmaster. 1990. Forage Losses Equal Economic Losses, So Minimize Them. Agr. Engr. Fact Sheet, PM-107, The Pennsylvania State University).

Other factors influencing quality

Several lesser factors also can influence forage quality. Weeds can negatively affect quality, especially in the case of noxious weeds. Insect pests can lower forage quality, particularly if they cause significant leaf loss. Plant diseases can affect quality when they result in a shift in the species present in the field and when they promote leaf senescence. Insects and diseases generally have their greatest impact on yield and persistence of forages.

Exceptions to the ranking

Forage crops that accumulate a significant quantity of grain may increase slightly in overall quality with maturity as grain content increases in the plant. Some species contain anti-quality factors that can lower animal performance. Variety can become the most important forage quality factor in cases where varieties are developed to significantly reduce or eliminate species anti-quality factors, as in low-alkaloid varieties of reed canarygrass. Harvest and storage of a forage crop at a moisture content leading to spontaneous combustion would plainly become a most important factor. Or, if prolonged flooding or drought threatens a forage crop, environment becomes as important as any of the other factors. Certain soil fertility conditions, such as a very low pH, could eliminate alfalfa from a mixed seeding, thereby changing the species composition of the stand and greatly diminishing stand quality.

Significance of the Ranked Factors

All of the ranked factors mentioned earlier can be controlled to some extent through proper management. For example, maturity can be controlled by adjusting harvest dates. The highest quality species that fit the available soil resources should be chosen. Drying agents and preservations may help to avoid rain-damaged forage. Soil testing can identify optimum lime and fertilizer additions. Although variety selection is very important for yield and persistence, it is of relatively less value to forage quality.

Attempts are being made to modify alfalfa plant composition and leaf-to-stem ratio through breeding, as with the multi-leaf alfalfas. Chemical analyses are the selection criteria. Several alfalfa trials throughout the United States, including Pennsylvania, now include forage quality in their evaluation of new varieties. At a given trial site, all varieties are harvested on the same date and then evaluated for forage quality. Any differences in maturity among varieties could influence the ranking of those varieties (Table 1). In other words, some of the reported differences in forage quality between varieties may only be reflecting that they were harvested and compared at different maturities. Keep in mind that maturity is the most important factor influencing forage quality.

Table 1. Relationship between net energy of lactation (NEL) and relative maturity (mean stage by count, MSC) for several varieties in an Indiana alfalfa variety trial.
VarietyNE (Mcal/lb)Maturity stagea
aThe higher the maturity stage number, the more mature the alfalfa. A stage reading of 3.0 is at an early flower stage.
bIn the trial, Multileaf-A and -B were selected for the multi-leaf trait.
cHigh quality-A was selected for high quality. High yield-A and -B produced two of the highest yields of 44 varieties tested in the trial.
Vernal0.712.7
Multileaf-Ab0.753.2
Multileaf-Bb0.752.4
High quality-A0.771.4
High yield-Ac0.703.2
High yield-Bc0.703.3

Selection for forage quality in corn silage is now being done, and it is likely that many commercial companies will be promoting hybrids on this basis as well. Preliminary studies at Cornell University, Michigan State University, and the University of Idaho indicate that there is a range in overall silage quality among hybrids. It may be possible to breed for higher stover quality while maintaining a high grain-stover ratio, and develop a silage hybrid with overall higher digestibility. As with alfalfa, selection may be based on chemical in vitro analyses, with little or no actual animal performance data to back up forage quality claims. This means that varieties ultimately will be compared for animal performance on the farm by the forage producer. Claims of improved forage quality may be added only after those varieties excel in animal performance tests.

What Determines Quality?

Plant composition

All forage plants are composed of cells having fibrous cell walls for support and protection. Contained within the cells are several soluble compounds, most of which are highly digestible (Figure 1). Since cell wall material is the primary constituent of forages, one of the main objectives of forage analysis is to characterize the cell wall fiber.

Plant fiber has three major components: cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are digestible to some extent by ruminants. Ruminants can convert these fiber components to energy because the rumen provides the correct environment for bacteria and other microorganisms that actually break down the fiber. Lignin is indigestible, and thus cannot be used by ruminants for energy.

Plant morphology

Both grasses and legumes have two main plant parts, leaf and stem. As a structural component of the plant, stems typically contain more fiber for support. Leaves, on the other hand, provide a means for capture and utilization of energy from sunlight and tend to be lower in fiber content than stems. Given the large difference between the digestible fiber of stems and leaves, the proportion of leaf to stem in a given forage plant relates directly to its forage quality.

How is Quality Determined?

Physical appraisal

Appraisal of a forage based on sight, smell, and touch can provide some general information, but chemical analyses are needed to asses the economic potential of the forage.

At a recent forage meeting, approximately 80 forage producers and industry people were asked to rank four bales of hay by a visual appraisal of their forage quality. The hay ranged from pure alfalfa to an alfalfa-grass mix. An objective quality evaluation of the same bales, based on relative feed value (RFV), found considerable differences among them. There was no consistent pattern in the ratings by individuals but, in fact, the bale judged best on the basis of appearance had the lowest RFV of the four (Figure 3). Clearly, objective forage analysis is required.

Figure 3. Visual appraisal versus chemical (RFV) ranking of alfalfa and alfalfa-grass hay bales. Percentages are first-place rankings by visual appraisal for each bale.

Chemical analysis

The Van Soest Fiber Analysis System separates feeds into distinct fractions that relate to their nutritive value. Neutral detergent fiber (NDF) consists of the total fiber in the forage and relates negatively to forage intake by ruminants. Acid detergent fiber (ADF) is composed of highly indigestible fiber and relates negatively to forage digestibility. Total nitrogen concentration in the forage (usually expressed as crude protein) is also a useful measure, since adequate intake of nitrogen is essential for animal productivity.

Forage laboratories analyze samples for NDF, ADF, and total nitrogen. It is also possible to accurately estimate these components using near infrared reflectance spectroscopy (NIRS). Other estimates of forage quality, such as total digestible nutrients (TDN), net energy of lactation (NEL), and relative feed value (RFV) are derived from mathematical manipulations of NDF and ADF values.

Proper sampling

Clearly, forage quality can be extremely variable and, as in soil testing, proper sampling technique is essential. Without a representative sample, the results from a laboratory analysis are useless. When an alfalfa-orchardgrass hay bale was sampled correctly with a coring device and compared with a grab sample taken from the same bale, their analyses differed considerably (Table 2). A University of Minnesota study showed a large range in quality in a single load of baled hay where NDF values ranged from 34 to 54 percent among individual bales. Good sampling technique, therefore, must involve using the proper sampling equipment, and taking an appropriate number of sub-samples.

Table 2. Alfalfa-orchardgrass hay bale sampled by two methods.
ConstituentSampling Method
CoredGrab
Crude protein, %1613
Neutral detergent fiber, %5663
Acid detergent fiber, %3742
Net energy of lactation, Mcal/lb0.560.49

What is Quality Forage Worth?

The value of high quality forage in a balanced ration is evident in Table 3. When three hays of low, medium, and high quality, are used with corn silage and a mixed feed grain to balance a ration, total feed cost for the high quality hay ratio is $0.11 less per cow per day than the medium quality hay ration. Income over grain cost is $0.45 more per cow per day for the high quality hay ration than for the medium-quality hay. For 100 cows over a year, this difference is greater than $16,000. Low quality hay does not allow an animal to consume enough digestible energy to be highly productive. A hay of lower quality than the three hays in Table 3 would substantially depress the performance of high producing dairy cows.

Table 3. What is forage quality worth?
Forage typeLow quality hayMedium quality hayHigh quality hay
Note: Assumes second-lactation, 1,350- lb cow producing 60 lb milk/day containing 4% milk fat with a milk price of $11.00/cwt. Adapted from the Forage Production Manual for the Pro-Dairy Program. Cornell University, Ithaca NY 14853.

aGrain is a mixed dairy feed.
Hay composition
Crude protein, %121518
Net energy of lactation, Mcal/lb0.510.580.65
Balanced ration
Hay, lb131417
Corn silage, lb333744
Grain, lba252217
Feed costs
Hay, $/ton7085100
Silage, $/ton242424
Grain, $/ton180180180
Total feed cost, $3.113.022.91
Income over grain (IOG), $4.354.625.07
ICG x 100 cows x 365 days, $158,775168,630185,055

Keeping Quality in Perspective

If you want to produce high quality forage, keep in mind the ranking of quality factors and their relative contribution to quality. While all six factors described are important, using high quality varieties will be advantageous only when the other five factors are operant. Quantity (yield) of forage is also a major consideration. Evaluate your total forage requirements, and then select the crop and the appropriate acreage of that crop that best meet the needs of the group or groups of animals to be fed. It ultimately comes down to economics; high quality forage can help keep farmers in the dairy business.

Prepared by Jerry H. Cherney, associate professor, Department of Soil, Crop, and Atmospheric Sciences, Cornell University; and Marvin H. Hall, professor, Department of Plant Science, The Pennsylvania State University.

For nearly four decades, scientists have been refining the ability to test forages for quality.

This research is being done in an effort to improve animal nutrition and, consequently, animal production. In the past, analytical procedures required a week or more to complete. They can now be done in less than 10 minutes, with greater accuracy than before.

As procedures for analyzing forages have improved, knowledge of how to use test results to increase animal efficiency and performance has also improved. Despite these advancements, many livestock producers still do not recognize forage quality testing as a valuable management tool.

Why Should I Test Forages for Quality?

Greater net profit is the primary reason livestock producers need to know the quality of forages they are feeding. Not knowing the forage's exact quality acts as a two-edged sword that can cut into profits either way it swings. The examples in Table 1 are simplistic, but the costs are real.

Table 1. Costs associated with not knowing forage quality when balancing a dairy ration.
SituationPercent crude proteina in:$/cow/day$/100 cows/day
HaylageCorn silageRation
adry matter basis
Actual forage crude protein19.38.816.02.72272
Farmer estimates crude protein below actual and balances ration accordingly17.3
7.816.92.81281
Farmer estimates crude protein above actual and balances ration accordingly21.39.815.02.66266

Dairy producers who estimate the crude protein (CP) content of their haylage to be 2 percentage units lower than it is, and the crude protein content of their corn silage to be 1 percentage unit lower than it is, end up feeding more supplemental protein than necessary (see Table 1). This extra crude protein in the ration will add $0.09 per cow per day in feed costs. For a herd of 100 cows, this is equivalent to $9.00 per day. It would take just a little over 3 days of not knowing the quality of the forages and feeding extra protein, as in this example, to pay for the cost of quality analyses. (Forage quality testing usually costs less than $15.00 per sample.)

The other edge of this two-edged sword cuts into profits when forage quality is overestimated. Table 1 shows that estimating forage crude protein to be greater than it is results in adding insufficient supplemental protein to the ration and saving $0.06 per cow per day in feed costs. Unfortunately, the cows are being "short-changed" of crude protein, and this can lower milk production, especially in early lactation.

Guessing at fiber and mineral content also will have an enormous economic impact. For example, the neutral detergent fiber (NDF) content of a forage helps determine how much of the forage an animal will consume. Estimating the NDF too high or too low can adversely affect intake, animal performance, and health. Knowing the actual NDF content not only saves or makes more money, it also allows managers to provide better animal nutrition. Better nutrition results in greater production and improved efficiency (pounds of milk or weight gained per pound of feed consumed).

Knowing the quality of the forages you're selling or buying is economically wise as well. This fact is confirmed at Pennsylvania hay auctions, where hay quality is analyzed and the results posted on each load of hay prior to the auction. At auctions during 1990-91, each percentage-unit increase in the crude protein of hay resulted in a selling price of $8.00 more per ton (Table 2). Selling 10 tons of 20 percent CP hay as 18 percent CP hay because the quality was not tested will cost the seller about $160.00. On the other hand, buying 10 tons of 18 percent CP hay as 20 percent CP hay will cost the buyer $160.00.

Table 2. Relative feed value (RFV), crude protein (CP), and sale price of hay sold at hay auctions in Pennsylvania during 1990 and 1991.
RFVCP
(%)
Sale price of hay when quality was known ($/ton)
11518144
12420160
13322177

Collecting Samples of Baled Hay

  1. Take a separate sample from each field and cutting.
  2. Always sample with a bale corer such as a Penn State Forage Sampler. It is impossible to get a representative sample using bale slices.
  3. Insert the sampler to full depth into the end of each bale to be sampled. This will insure an accurate sample.
  4. Take at least 20 widely separated sample cores from each lot.
  5. Mix the 20 cores in a clean pail and place in a clean, airtight plastic bag.
  6. Label each bag clearly with your name, address, sample number, forage mixture, stage of maturity, and date harvested.

Collecting Samples of Haylage and Silage at Harvest

  1. Take sample as the silage is placed in the silo. Silage from silos with excessive seepage should be resampled upon feeding.
  2. Collect three to five handfuls of haylage or silage from the first load of the day in a plastic bag, and place in refrigerator or freezer immediately.
  3. Follow the same procedure for several loads of forage throughout the day. Combine samples and mix well to obtain a representative sample.
  4. Repeat for each field if more than one field is harvested in any one day.
  5. Throw styrofoam egg cartons of different colors into the blower at the end of each lot. This will aid you in identifying the lots later as the feed is unloaded.
  6. Label the bag clearly with your name, address, sample number, forage mixture, stage of maturity, and date harvested.

Collecting Samples of Haylage and Silage from Storage

  1. Collect a 1- to 2-pound sample from the silo as it is discharged from the unloader.
  2. Do not collect samples from spoiled material on top of the silo. In upright silos, wait until 2 to 3 feet of silage has been removed.
  3. Collect samples from the morning and evening feedings over a 2-day period.
  4. Mix the samples thoroughly, place in a clean plastic bag, and seal.
  5. Store immediately in a cold place, preferably in a freezer, until analyzed.
  6. Label the bag clearly with your name, address, sample number, forage mixture, stage of maturity, and date harvested.

Preparing and Storing Collected Samples

Keep hay samples in a cool place. Keep haylage and silage samples frozen in an airtight container, then mail them in insulated bags--preferably early in the week--to prevent bacterial decay that might alter the results.

Remember: the results will only be as good as the sample taken. Follow the above steps to collect a representative sample for an accurate analysis.

Where do I send Forage Samples for Analysis?

Once you have gone to the effort of collecting a sample correctly, how can you be sure the results you receive from the testing laboratory are accurate? Concerns about laboratory testing often focus on methods used for determining forage quality. Concern should be focused, however, on the accuracy of results and not on the technique used. To help you determine if test results are accurate, we have listed some questions to ask the laboratory manager:

  1. Is the lab certified or does it participate in a check-sample program (also called a proficiency testing program)? The National Forage Testing Association has a certification program that compares a laboratory's performance with that of other labs to warn of potential inaccuracies. The American Association of Feed Control Officials conducts a check-sample program that insures consistency and accuracy among participating labs. Involvement in either program indicates that the laboratory is concerned with the accuracy of its results.
  2. Does the lab include duplicate samples or quality control check samples in each group of samples analyzed? One of the easiest ways for a laboratory to monitor results is by analyzing replicates of a sample. If the analyses for replicates are not similar, there is a problem in the testing procedure. In addition, the inclusion of standards or check samples (material of known quality) in each group of samples analyzed can indicate if the analytical procedure is working correctly or not. Standards or check samples can also alert the laboratory technician of small changes in results over time and allow corrective steps to be taken.
  3. What analytical methods does the laboratory use? There is more than one method of analysis for most plant constituents. Laboratories should use methods that are well validated and approved by the Association of Official Agricultural Chemists.

    Laboratories that use near infrared reflectance spectroscopy (NIRS) to analyze forage for quality can be asked three additional questions that will help determine if the results are accurate. Like other laboratory analyses, NIRS analysis is sophisticated and should be conducted and monitored by trained personnel.

  4. How often are NIRS instruments and calibration equations monitored? NIRS instruments should be monitored by running a check sample daily or after every 25th sample, whichever is more frequent. Calibration equations should be monitored by conducting laboratory analyses on every 25th sample. Again, this additional monitoring adds extra costs that will increase the fee charged for each sample.
  5. Does the laboratory do chemical analysis in addition to NIRS? NIRS methods are based on calibrations derived from chemical methods. NIRS labs without a chemical analytical capability have no way to monitor the reliability of their calibration equations. It is not impossible for a NIRS-only lab to have a good monitoring program. But monitoring is much more difficult, since all of the monitoring samples have to be sent to another lab for chemical analysis.
  6. How does the lab identify and analyze inappropriate samples received for NIRS analysis? Each NIRS calibration is specific for a particular type of sample. For example, corn silage is most accurately analyzed with a calibration equation developed for corn silage and not a calibration equation developed for alfalfa haylage. A lab should have a procedure for identifying samples that are inappropriate for the calibration equation and a protocol for properly analyzing these samples.

Keep in mind that laboratory monitoring practices increase the cost of analysis. Asking these six questions will help you evaluate a laboratory and become more knowledgeable about purchasing analytical services.

Laboratories generally report results of analyses as a single number. This does not mean that a hay sample testing at 20 percent crude protein is exactly 20.0 percent CP. Instead, it means that the hay is 20.0 percent CP plus or minus some variation. The amount of this variation will differ from lab to lab and from method to method. A variation of about 3 percent can be expected between labs for measurements of CP. In other words, a hay sample testing at 20 percent CP at one lab is expected to test anywhere from 19.4 to 20.6 percent CP at another lab or at the same lab if the analysis is repeated. Variation is usually much higher for fiber measurements than for crude protein measurements.

Prepared by Marvin H. Hall, associate professor of forage management, and Virginia A. Ishler, extension assistant in dairy and animal science. Portions of this publication are taken from How to Evaluate a Forage Testing Laboratory, South Dakota State University Agric. Exp. Stn. Bulletin C255.

Five dairy farms in the northeast participated in a study designed to describe a technique called "mob grazing."

We have since learned that most dairy farmers call mob grazing "high density" or "tall grazing." The cattle are grazing pastures higher and leaving higher grass residuals, while the farmers are still striving for high quality forage. Each farm has resource challenges and opportunities that impact their ability to use this practice. Our goal was to try and collect data and later interview the producers to understand their management goals and practices.

Mob Grazing: What Is It?

Motivated by livestock farmers in dry or low quality soil environments, some farmers have been trying to improve soil quality through residue management. They allow pasture grasses to grow taller than the traditional 8-10 inches and allow animals to consume and trample the sward. In the farm press and publications, growers report impacts to animals such as increased weight gain and finishing, less costs to feed animals, and improved soils. Unfortunately, there has been little research-based information to share with farmers and farm advisors regarding this practice.

Given this background, there is some skepticism as to its adaptation to dairy production. Dairy producers are looking for high quality feeds for lactating animals. In this study, we attempted to gather a record of practices that innovative dairy producers were adopting. The study was initiated in 2012 and continued into 2013.

Background information about the five dairy farms

Farm description

Farm 1Farm 2Farm 3Farm 4
Acres of pasture620240260200
No. milk cows27060235145

Pasture allotment

Farm 1Farm 2Farm 3Farm 4
Pasture size, acre12-42-2.51
Cows/pasture13550245145
Pasture size/cow/d, acres0.030.06-0.080.020.01-0.02
Grazing cycle28-30 dWhen rested18-24 inch35 d
Forage remaining30%30-50%30-40%40%
Moves per day12-522
Hours on pasture20202020
Distance to barn, miles0.190.04 - 1.500.11 - 0.500.04 -0.75

Supplemental feeding

Farm 1Farm 2Farm 3Farm 4
Stored feeds, if anyHaySilageHay + SilageSilage +Baleage
Graze in winter?If weather permitsUntil Dec.NoNo

The Take-Home Messages About This Study

Experience Helps

All participants had been using managed intensive grazing (MIG) before adopting "tall grazing." They are experienced pasture managers. Several mentioned they adopted grazing over 20 years ago (late 1980's to the mid-1990's). They have been trying to use some variation of "tall grazing" for 2-8 years. Their responses for making this change ranged from labor and machinery savings, continuing to provide a forage diet to cows, thought of as "natural" and matching the productivity of the soil to a forage cropping system.

Forage Quality Was Excellent

Does tall grazing give superior results for pastures? We did not find that this was "superior" nutrition. Forage samples were taken in the same paddock at each rotation and sent to the Dairy One Forage Laboratory, Ithaca, New York. All forage sampled was excellent. With time, the forage quality actually improved.

Crude protein (CP) of the forage improved through the grazing season, averaging 20% dry matter (DM) at the June /July grazing sessions with a maximum average CAP of 28.5% dry matter (DM) during the Sept.-Nov. grazing event.

Neutral detergent fiber (NDF) decreased from an average of 52% to 34% from the June-July to the September-November grazing event.

The Net Energy at Lactation (NEL) ranged from 0.61 to 0.73 Mcal/lb DM between these two grazings, respectively.

These improvements in forage quality later in the grazing season may have been a result of being grazed at a less mature stage of growth. This may have been due to:

  • The first grazing being over-mature due to rapid early-season growth, or due to the forage plants being less mature during each successive grazing.
  • Summer slump conditions forcing farmers to return to these paddocks a bit sooner than anticipated to maintain minimum pasture dry matter intake requirements as all farms participating in this study were certified organic.

Dry Matter Production is Affected by Drought, Stocking Rate

Are we getting more dry matter (DM) production because these dairy producers are grazing tall? That was difficult to determine in one year due to a summer "mini-drought." In all cases, producers had to supplement feeding in the summer months. In today's economic climate, this is very costly for a dairy farm. Some producers are recognizing they must match the dry matter production of the farm to the stocking rate of animals.

Trampling and Stocking Rate

Researchers evaluated the paddock before and following grazing by cows. They found that the forage consumed ranged from 50 to 70% of total forage available. Cows consumed the greatest percentage of the canopy cover in the top layers (averaging 75% consumption in the top 8" of growth), with lower layers (0-8") having less total consumption (averaging 53%).

Most of the growers are aware that the "popular literature says" to leave a lot of residue to build the soil. Farmers told us they moved cattle more frequently if the forage quality was not ideal, leaving more grass as residue. Some of the comments about practices are as follows:

  • Tries to leave some forage standing - goal is 25%/50%/25% (standing, eaten, trampled)
  • "Take the leaf and leave half"- goal is to graze 60-70% and leave 30% behind
  • Goal is to leave 50% behind, when actual is probably 25-50%
Grazing Comparisons, Dairies in the Northeast
High Density Stock Grazing Producer Applications in NE
250,000 lb. /acre + stocking density. 44,000-337,000 lb./acre
90 days forage rest 40-78 days of forage rest
Moving 2-3 times daily Moving 2 times, sometimes more per day

Conclusion

The beauty of pasture is that it can be managed in many ways. There are no strict "formulas" as aspired to some of the definitions in the popular literature. It is possible for dairy graziers to manage pasture height "taller" and to stock at a higher rate but one still needs to manage for quality to sustain milk production. Dairy producers that are beginning graziers would be wise to gain experience managing for dry matter and quality as primary goals and then move towards a system incorporating this "hybrid" approach.

Acknowledgements

  • Mena Hautau, Extension Educator, CCA - Penn State Extension-Berks County,
  • Dr. Kathy Soder, Melissa Rubano, Aimee Hafla - USDA Pasture-ARS-Pasture Systems and Watershed Management Research Unit
  • Brian Moyer, Program Assistant - Penn State Extension-Berks County

This study was funded by Northeast Sustainable Agriculture Research and Education Program - USDA, 2012, Partnership Grants Program.