Gayle Smith
for Tri-State Livestock News

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September 25, 2012
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Don't feed more than you need – Get a feed analysis


With forage supplies tight, extension specialists are urging ranchers to analyze their forages for nutrient content. According to Rick Rasby, beef specialist with the University of Nebraska, producers would be surprised how much forages can vary in nutritional value.

During a recent webinar on feed analysis and nitrate testing, Rasby told producers about samples he had taken at a stackyard on alfalfa and native grass hay. “We sampled a stackyard of alfalfa, and it ranged from 23 percent to 13 percent crude protein. The native hay ranged from 10 percent to four percent crude protein,” he explained. The NRC requirements suggest alfalfa averages 15 percent crude protein and 56 percent total digestible nutrient (TDN), and native hay typically averages six percent crude protein and 52 percent TDN.

If a forage has 52 percent TDN, it will be difficult for that forage to meet the cow’s nutritional requirements after calving by feeding it alone. “As you move closer to 56 percent TDN, the forage may be able to meet the cow’s nutrient requirements prior to calving, but you may need to add a little energy after calving to meet her nutritional requirements because they will be higher,” he explained.

“What is important to note from all of this, is not all forages are average,” Rasby continued. “That is why it is important to get your forage analyzed, and why it is important to collect a good sample.”

Taking the sample

Producers can access videos through the University of Nebraska’s YouTube channel, NU Beef, to learn how to sample hay. These videos show samples being taken from a big round bale, and from a pile of ground hay. They also give step by step instructions for the sampling process.

“It is very important when sampling hay to get a representative sample,” Rasby explained. “Don’t take grab samples on forages. You will need to use a hay probe, which can usually be borrowed from your local county extension office,” he explained.

Rasby said if a producer has 20-25 big round bales of hay, 10-12 of those should be sampled to get a good, representative sample. When sampling hay, never sample first, second, third and fourth cuttings of hay together. “All of those should be separate samples,” he said. “Early-cut and late-cut hay should also be sampled separately, as well as different varieties like sorghum sudan grass hay and millet hay.”

After the samples are taken, it is important to identify the sample properly so the lab analyzing the sample has a good understanding of what is in the bag. “The forage analysis will only be as good as the sample you have taken,” he said. Typically, most forages are analyzed in the lab using NIR (Near-infrared Spectroscopy), which is a quick and accurate way to identify the nutrients in the forage. Results can typically be received within two to three days of sending a sample in, if producers send it at the first of the week.

Test annual forages for nitrates

“This year, I would highly recommend testing any annual forages for nitrates,” Rasby said. Cattle can be poisoned when nitrate levels in the forage they are consuming is too high. Nitrates are converted to nitrites in the rumen, then to ammonium, then to crude protein, Rasby said. When cattle are exposed to high levels of nitrates, many times they don’t have the bugs in the rumen to convert nitrites to ammonium, so the nitrites are absorbed into the bloodstream. This process reduces oxygen to the tissues of the animal. At that point, the oxygen-carrying capacity of the animal is reduced, the blood will turn a chocolate color, and the skin will change to a bluish color. If the animals aren’t found immediately and treated, there is a possibility of death, Rasby said.

“Cattle can be adapted to high nitrates in feeds,” Rasby continued. “But, you have to adapt them so that the bacteria in the rumen can convert nitrates to nitrites to ammonia,” he said. Feed additives are available that can assist a rancher with this, Rasby said, reminding producers it is very important to manage the cattle properly so they don’t get nitrate toxicity.

Reading a feed sample for nitrates

Rasby said if a producer requests a nitrate test on a feed sample, the test will typically show if the nitrate level in the feed is at a safe level, caution level, or if the producer needs to dilute the feed with another forage low in nitrates. Many times, this information will be listed on the bottom of the analysis and will say nitrates or nitrogen, he said. “Make sure you understand if it is at a safe level, or if it needs to be diluted,” he explained.

If a forage does need to be diluted, Rasby said grinding it with another forage is ideal. “If you have the grinding ability and feeding ability on your operation, you can dilute those higher nitrate feeds down to a safe level,” he said. “Remember that grinding doesn’t do anything for forage quality. Basically, grinding only reduces the particle size and will increase intake, but it doesn’t improve forage quality at all,” he added.

For more information about testing forages, Rasby 402-472-6477, or by email at: rrasby1@unl.edu




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Tri-State Livestock News Updated Jun 23, 2016 05:38PM Published Oct 9, 2012 09:29AM Copyright 2012 Tri-State Livestock News. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.