Quarrels About Quality: 14 Sources of Variation in Forage and Hay Testing

When it comes to hay testing, producers commonly grumble about the variation in Relative Feed Value (RFV) and protein content, based on their observations and what the lab reported.

Producers often have these concerns, because the RFV determines the price of a forage and how much customers are willing to pay.  An underestimated RFV can result in decreased profit for forage producers.  A couple weeks ago, I attended the NIRS Consortium annual meeting where Rocky Lemus gave a very informative talk about the importance of proper sampling, which addressed the producer concerns I often hear.  Variation in forage test results can come from in the field, storage, sampling, and in the lab. Here are 14 common sources of variation within a forage sample:

 

  1. The leaf : stem ratio, forages with a higher leaf : stem ratio are typically higher in protein and RFV. This is because the leafy portion of the plant contains more protein than the stems. Additionally, the stems are a structural part of the plant containing higher amounts of fiber.  Acid detergent fiber (ADF) and neutral detergent fiber (NDF) are used to calculate RFV therefore, forages and hays with more leaves and less stems are lower in ADF and NDF and higher in RFV.

 

  1. The weed content of a forage can affect the RFV. Weeds are high fiber plants, so the more weeds contaminating the forage or hay the lower the RFV. Weeds also tend to be lower in protein, thereby also affecting the nutritional content of the forage.

 

  1. Baling conditions can also affect the RFV of a hay. If hay is baled under moist conditions or after having been rained on, the water-soluble sugars have been removed from and plant. The percent of ADF and NDF are increased due to the absence of sugars.  The result is a RFV and lower energy forage.

 

  1. Species of forage also affects RFV. This is not news to hay producers or livestock feeders.  It is well understood that legume forages such as alfalfa and clover are typically higher protein and higher RFV, than grasses.  This is a result of the leaf : stem ratios.

 

  1. The maturity of a plant can also affect the feed value. Older more mature plants are more fibrous, and they typically have a lower RFV than a lush growing forage.                     plant maturity

 

  1. Fertilization can result in higher protein in a forage and lower ADF and NDF. Fertilization management may help produce high quality forages. Be cautious to avoid creating a high nitrate forage by applying too much fertilizer.

 

  1. Proper storage of a baled hay is very important. Reduce ground contact as this will result in accumulation of moisture from the ground and a decreased RFV. Protect your baled hay from the elements to avoid losses of soluble sugars and protein.  Wind and rain alike can remove the leafy portion of the plant thereby decreasing protein and RFV.

 

  1. Division of forages into separate lots can affect the accuracy and representation of a forage sample. Lots should be defined by both species and field from which it was baled. For example:  If there are three fields two alfalfa and one grass, the lots need to be separated by not only species, but also field as one location may have a differing quality that the other based on management, precipitation differences, or topographical differences.  Therefore, I would send three separate hay samples to Ward Laboratories, INC. for NIR testing.

 

  1. Proper sampling procedure is very important. Using a hay probe is the key to ensuring a representative sample. Hay probes can accurately represent the leaf : stem ratio, whereas using a hand grab can result in the leafy portions falling through fingers and obtaining an overrepresentation of stems and a lower RFV.  Additionally, with a hand grab only one layer of the bale can be grabbed and to ensure a representative sample it is important to sample several inches inside the bale.  For more guidelines and to become a certified hay tester visit the National Forage Testing Association.

 

  1. The number of cores taken is another source of variation when testing. The recommendation is to combine 20 randomly selected cores. The difference between taking 20 cores and 10 cores can cause variation in crude protein by up to 5%, meaning taking only 10 cores could either over estimate nutrient values or under estimate them.

 

  1. It is very important to ensure proper treatment of samples in delivery. If the sample is hay, it is typically dry enough to not have cause for concern. If it is a fresh forage clipping, check the moisture, if it is very damp rotting can occur on its way to the lab in just a few days stuffed in a box with other samples or envelopes.  Of course, the portion of the plant that rots first is the leaves, so the RFV decreases when this happens on the way to the lab.

 

  1. Splitting in the lab can also affect RFV. Ward Laboratories, INC. uses the cone and quarter method on all forage samples that come in the lab. It is very important that when the lab splits the sample for the portion to be tested it represents the sub sample given to us.  Sometimes, it is requested to send the sample on to other labs, when this happens, the sample is split into two – three sub samples and the NIR scans are checked to ensure the sub samples nutritional values repeat.  This way we can keep some sample in our lab in case further testing is requested and it is a good way to check that our sub-sampling procedure is accurate.                                                                                                                                                                                                                                                      img_2506-e1517945202593.jpg

 

  1. Drying of the sample in the lab can result in heat damage to the sample therefore again decreasing RFV. Ward Laboratories, INC dries samples in an oven at 64°C before grinding, the typical dry matter after grinding is between 95-97% dry matter. Other labs use microwave ovens for faster drying time, however using a microwave does result in higher incidence of heat damage to samples.

 

  1. Grinding of the sample can also make a difference as to how it scans NIR. Ward Laboratories, Inc. grinds samples through a 1mm screen. More coarse grinding can cause inaccurate results on the NIR instrument.

 

When questioning results of a forage or hay sample, consider all the sources of variation that went into that sample. Sampling plants is tricky business as it is a variable material.  Always do your best to take a representative sample.  Call the lab if you have questions or concerns before taking your sample or interpreting your results.

 

 

 

 

4 Considerations For Feeding Hail Damaged Forage And Crop Residues

 

Here in Central Nebraska we have experienced several mid-summer thunderstorms. These hail producing storms have wreaked havoc on crops and forage productivity, particularly in the Broken Bow and Ansley areas. As producers move forward with crop insurance, they will also be scrambling to utilize what is left of their standing row crops and forages. There are three laboratory tests I would recommend to make an informed decision about the remaining forage. Then depending on the results of your laboratory tests, you can determine what your most economical option is.

1. Nitrates

Defoliation due to the pounding hail results in decreased photosynthesis within the plant. This means that the plant can not convert nitrates to protein. The root system of the plant still continues nitrogen uptake, although the plant cannot utilize these nutrients, resulting in the potential accumulation of nitrates in the plant. Nitrate (NO3 – N) levels between 1400 – 2000 ppm can result in abortions while levels higher than 2000 ppm can result in sudden death if not diluted with other sources of roughage. Therefore, nitrate testing of hail damaged forages is highly recommended before making a decision to graze, hay or ensile the forage.

2. Mold and Mycotoxin Potential

Hail damages the outer cell wall of the plant. The cell wall is an immune defense similar to skin on animals. It prevents infectious agents from penetrating, proliferating and using the plant as a food source. When the cell wall is damaged, opportunistic molds may infiltrate and grow. Consequently, when haying or ensiling forage, testing for mold counts is important. Mold counts above 1 million cfu/g impact animal health and lower production potential.
If the forage is a grain producing forage such as corn or milo, a producer may want to inspect the crop to determine if grain has been produced. If there is grain and it is damaged by the hail, mycotoxins become a potential risk when feeding to livestock. Mycotoxins presence may be present even in the absence of a high mold count. If you suspect mycotoxins may be an issue, remember mycotoxins and molds are often produced together however, the absence of one mycotoxin does not mean conditions were not ideal for another mycotoxin to emerge. If haying the hail damaged forage, proper drying can cut down on mold and mycotoxin presence. If ensiling, proper fermentation and additives may reduce the risk of having these agents in the feed.

 

 

3. Relative Feed Value

The relative feed value (RFV) will be less in a hail damaged forage or crop than its intact counterpart. Defoliation caused by the hail results in the removal or the leafy mass of the plant and what remains is the stocks and stems. These parts of the plant are lower in protein and higher in fiber, which results in a lower relative feed value. Additionally, this also means lower total digestible nutrients (TDN), and net energy of gain (NEg), lactation (NEl), and maintenance (NEm). Therefore, when feeding hail damaged forage, testing the protein and energy of the feed is important to determine how much energy and protein supplementation will be needed to meet production goals.

4. Economics

The last thing to consider, and the most important to your bottom line, when determining how to feed a hail damaged forage is what is the most cost effective delivery system based on the results of feed reports. If the nitrate reports came back low and you have the means to supplement cattle in the field to meet energy and protein needs, grazing may be the most cost effective option. Haying may also be an option under that scenario, however, if selling the hay profit margins may be small do to the lowered feed value and potential mold risks associated. Additionally, when haying you must input equipment and fuel costs associated with cutting, windrowing, and baling. If the nitrates levels have been reported between 2000ppm and 3000 ppm ensiling the damaged forage may be a good option as the nitrates can decrease by up to 50% and then be fed back to the animal. Equipment, fuel and storage costs must also be taken into account for ensiling the feed. In the case of moderate nitrates, haying and mixing with a high quality forage, such as alfalfa, to both dilute the nitrates to the appropriate level and meet the difference in protein and energy provided by the damaged forage and the animals requirements, may also be a viable option. Finally, if the nitrates report is high, utilizing the forage as a fertilizer for next years crop may be the only option.

When determining how to best utilize hail damaged forage, always take nitrates, mold and mycotoxin risks into account as well as the lowered feeding value. Consider the man power, equipment, fuel and supplementation costs associated with each option. This will allow you to make the most informed and cost effective decision possible.