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Value of feed: Feed analysis prevents over-utilization of resources

by Wyoming Livestock Roundup

Feed analysis prevents over-utilization of resources

With forage supplies still 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.

Rasby told producers about samples he had taken of alfalfa and native grass hay. 

“We sampled a stackyard of alfalfa, and it ranged from 23 to 13 percent crude protein. The native hay ranged from 10 to four percent crude protein,” he explained. 

The National Research Council (NRC) requirements suggest alfalfa averages 15 percent crude protein and 56 percent total digestible nutrients (TDN), and native hay typically averages six percent crude protein and 52 percent TDN. 

If forage has 52 percent TDN, it is difficult for that forage to meet the cow’s nutritional requirements after calving by feeding it alone. 

“As forages move closer to 56 percent TDN, the forage may be able to meet the cow’s nutrient requirements prior to calving, but producers 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 forage analyzed and to collect a good sample.” 

Taking the sample

“It is very important when sampling hay to get a representative sample,” Rasby explained. “Don’t take grab samples on forages. Producers need to use a hay probe, which can usually be borrowed from their local county Extension Office.” 

Rasby said if a producer has 20 to 25 big round bales of hay, 10 to 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 the producer has 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 for nitrates

“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 turns a chocolate color, and the skin changes 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, producers have to adapt them so that the bacteria in the rumen can convert nitrates to nitrites to ammonia.”

Feed additives are available that can assist ranchers with this, Rasby said, reminding producers it is very important to manage the cattle properly so they don’t get nitrate toxicity.

Reading feed samples

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, Rasby 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 producers have the grinding ability and feeding ability on their operation, they 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.”

Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send questions and comments on this article to

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