Rick Rasby teaches you how to test your forage
May 15, 2012
With forage costs on the rise, beef producers need to find the best way to manage the hay resources they have available. According to Rick Rasby, extension beef specialist with the University of Nebraska, beef producers who purchase hay also need to be concerned with the quality of the product they are buying. Rasby recommends whether the producer is buying hay or growing it himself, he should sample the hay and have it analyzed at a laboratory. “Forage is becoming more and more expensive,” Rasby said. “Producers need to know what they are buying.”
“When you look at a bale of hay, it is hard to determine the quality of that hay just by making a visual appraisal,” he continued. “Hay can really vary bale to bale,” he said. “It is like buying a bull just by his phenotype. You can’t see the genetics behind it,” he explained.
“It is important to know the nutrient quality of a bale of hay, so if the hay is deficient in something, you know what supplements to purchase to fill the gaps,” Rasby explained. Hay is primarily used as an energy source, but alfalfa can also be used as a protein source if it is of good enough quality, he added.
Unless producers are concerned about hay being mineral deficient, they can take a sample and send it to a lab, where it undergoes an NIR analysis. The Near Infrared Spectroscopy (NIR) analysis uses an infrared light spectrum to measure the organic matter in the sample, Rasby explained. “What I like about this test is it is a rapid method of measuring nutrient value. It is accurate and quick, and most of the time you can send in a test and once they receive it, have the results back by email within 48 hours,” he explained.
During the analysis, Rasby said the reflectant is collected and measured against a sample in a library of different types of hay to determine nutrient content. “Most of the NIR libraries for hays are quite large,” Rasby said. “The larger the library, the more accurate the results will be.”
Because the NIR test isn’t a chemical analysis, it doesn’t recognize inorganic material like minerals. “It will give a measurement for calcium and phosphorus because they are closely tied to organic material, but a wet chemistry test will be needed to test for other minerals,” he explained.
Recommended Stories For You
The primary factor that affects the quality of forage at harvest is the maturity of the forage at harvest, Rasby said. Alfalfa will typically average 15 percent crude protein, and 56 percent TDN, while native hays average 6 percent crude protein and 52 percent TDN. “As the maturity of the hay increases, the quality will decrease. This is because most of the nutritional value is in the leaves, which start to fall off as the hay matures,” Rasby said. “Tonnage will also increase as maturity increases, which presents a dilemma for the producer as to when is the best time to harvest the hay and get the most value from it,” he added. “If alfalfa averages 18-20 percent crude protein, it’s considered high end,” he said. “If it is closer to 12 percent, it is considered lower quality.”
Because the quality of hay can vary so much, Rasby recommends producers test their hay for moisture, crude protein, and energy (TDN). If they are planning to feed a summer annual forage like sorghum sudangrass or millet, the hay should also be tested for nitrates. “High nitrates can easily crop up in forages grown under drought conditions, and especially forages grown under drought conditions and fertilized with high nitrogen fertilizer,” he said.
If a forage comes back high in nitrates, it can still be utilized, Rasby said. “The lab will tell you the level of toxicity. It will say it is okay, moderately high, or high,” he said. “Solution of pollution is dilution. If you have hay high in nitrates, you can still feed it. You just need to dilute it with another forage not high in nitrates to prevent nitrate toxicity.”
Rasby said he has seen instances where producers run into problems with nitrate toxicity after cattle come off a cornfield and are fed a hot bale. When an animal gets nitrate poisoning, nitrates get into the animal’s bloodstream and starve the animal of oxygen causing them to go down,” he said.
One way producers can avoid nitrate problems is by setting the cutter head higher when harvesting an annual forage. “Most nitrates are in the bottom six to eight inches of the plant stem,” he said.
Producers should determine what they have in the stackyard so they feed the right quality of hay to the right animals. Heifers and especially heifers after calving have the highest protein requirements, so feeding a higher quality of alfalfa can help them meet their nutritional needs. “On the other hand, most cows can get by with 8-9 percent crude protein before calving, so they don’t need as high of a quality forage,” Rasby stated. “However, after calving their nutritional needs are higher, so they may need a better quality forage at that point,” he added.
Hay should be sampled using a hay probe, Rasby said. A producer can purchase one, or inquire at their local extension office about borrowing one. When using the hay probe, Rasby said it is important to plunge after each sample so it doesn’t become stuck in the barrel. He also encourages producers to take care of the tips of the hay probe. A powerful drill will also be needed to operate the hay probe for best results. “Tight bales are easier to sample than loose bales because they are easier to probe,” he said.
Rasby recommends each cutting of alfalfa be sampled separately. Native hay should be sampled by field, and by cutting since hay can be early cut, middle cut, and late cut. Native hay quality will change throughout the season, he said.
Producers should sample one-third of their bales to get a good, representative sample of the forage. If the sample is too big to fit into one bag, Rasby recommends either sending in more than one sample, or mixing the sample until it fits into one bag. An easy way to mix the sample is to lay out some newspaper and dump the sample onto it. Then, mix the sample, half it, and quarter it. Repeat the process until the sample will fit into one bag, he explained.
“It is important to take a sample that is representative of what is in the field,” he said. “Use a forage probe, and package the sample properly. Don’t dry it down or squeeze the air out of the bag,” he said. “It is also important to fill out the paperwork correctly, accurately identifying the sample. Be specific,” he added.