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Myths about NPN

If you could get the same productivity out of your cattle for less cost, wouldn’t you consider it? The practice of utilizing non-protein nitrogen (NPN) in ruminant feed does just that! Use of NPN-containing supplements is a long established, successful practice. However, many misconceptions still persist. The purpose of this article is to explore the science behind the use of NPN, including advantages and disadvantages of this practice so that cattle producers may form an informed decision 

What is NPN?

NPN or non-protein nitrogen refers to a source of nitrogen that is not derived from protein. Urea is the most common source of NPN in livestock feeds. Urea utilized in livestock feeds is a synthetic compound manufactured specifically for feed and fertilizer use. It is not harvested from urine of slaughtered animals. Synthetically manufactured urea functions in the same way within the rumen as naturally occurring urea.


Drought and excessive rains will result in low quality hay in many parts of the country

Drought and excessive rains will result in low quality hay in many parts of the country


Rumen Physiology

Rumen microbes break down most protein consumed and ammonia is produced as a by-product. Ammonia can be utilized in one of two ways. Microbes can use it to form microbial protein or, if ammonia levels exceed the microbes’ ability to utilize it, ammonia is absorbed into the blood stream where it is carried to the liver. The liver detoxifies ammonia and converts it into urea to be excreted into urine. A portion of urea is recycled back to the rumen through saliva. Enzymes in the rumen rapidly break down urea back into ammonia which can then be used by microbes or absorbed.

Rumen microbes use ammonia as a part of their diet. It doesn’t matter if it originates from true protein or NPN. Other necessary nutrients for microbial growth are carbohydrates and minerals. It is essential that ammonia be released simultaneously with available energy for ammonia to be converted into microbial protein. Also, phosphorus, sulfur and trace minerals must be present within the rumen environment in order for microbes to manufacture essential amino acids. The cow receives beneficial protein for its own needs when the bacteria and protozoa pass from the rumen to the abomasum and intestines where the microbes themselves are digested.


A diagram of protein metabolism and nitrogen recycling in the ruminant.

A diagram of protein metabolism and nitrogen recycling in the ruminant.


Advantages NPN

The primary advantage for use of NPN is cost savings. Addition of urea or other NPN sources to a feed supplement allows the effective crude protein level to increase for relatively low cost. Because microbial protein actually utilized by the ruminant animal is the same whether NPN or true protein is utilized, animal performance is maintained. Research has documented that proper use of urea or other NPN sources in healthy, mature ruminants does not result in a decrease in production and in cases of protein deficiency, production is actually increased.

Disadvantages of NPN

While NPN can be a great tool for cost savings there are some disadvantages to consider. If fed incorrectly, NPN can be toxic. Toxicity results when ammonia released from NPN exceeds microbes’ ability to convert it into protein. Excessive amounts of ammonia enter the blood stream, overloading the liver’s ability to detoxify.  Rumen pH rises and normal rumen function eventually ceases altogether. Death can follow.

NPN should not be utilized with lightweight calves, as their rumen microbe populations may not be adequate to properly utilize NPN. Also, calves less than a year old shouldn’t receive NPN as a major portion of their diet because the quality of microbial protein formed may be inadequate for their requirements. It also goes without saying that non-ruminants such as horses, pigs, etc. should not receive NPN.

Using NPN Properly

Supplements containing NPN offer an economical solution to increase effective protein in poor quality forages for less cost than “all natural protein” supplements.  These tips on proper NPN feeding will help avoid possible problems.

  • For simplicity, only use one type of protein supplement containing NPN at a time. If you must use more than one type, be sure to balance the ration so that no more than 25 to 30% of the total crude protein in the entire diet comes from NPN sources to avoid possible toxicity problems.
  • When choosing among free-choice protein supplements containing NPN make sure that consumption is regular and controlled so that cattle are unlikely to over-consume. Urea or other NPN sources are best utilized when consumed in small amounts over a constant period rather than slug feeding. Slow release of ammonia is preferred.
  • Do not feed NPN-containing supplements to horses, non-ruminants or ruminants without a functioning rumen. Refrain from feeding NPN to sick cattle that have impaired rumen function (for instance an animal recovering from acidosis or bloat). Also avoid feeding NPN to weaned calves less than one year old.
  • Do not feeds containing NPN to starved cattle, especially starved cows with calves at their side. Starved cows may try to consume greater than recommended levels, plus since milk production will be poor, calves may be forced to consume supplement as a substitute and receive too much NPN. Mature cows in good flesh receiving adequate forages can safely and effectively utilize NPN-containing supplements, even with calves at their side. Cows with adequate nutrition will provide enough milk so that calves will be very unlikely to consume enough of supplement to cause problems.
  • Do not feed urea-containing supplements to “shipped in” cattle that have been starved for several days. Give them a chance to overcome the stress of shipping and fill up on “all natural protein” supplements before introducing NPN-containing supplements.


Use of CRYSTALYX<sup>®</sup> Brand supplements containing NPN can help you stretch your hay supply

Use of CRYSTALYX® Brand supplements containing NPN can help you stretch your hay supply


In summary, use of protein supplements containing NPN can be an economically smart alternative for healthy, mature ruminants. When fed properly, NPN-containing feed supplements help to raise effective protein levels at a substantially lower cost than products containing 100% true protein. CRYSTALYX® supplement products containing urea are carefully formulated to provide safe levels of NPN. Slow consistent consumption of CRYSTALYX® supplements helps to optimize urea conversion to microbial protein. Just follow the simple guidelines on the product labels for safe and economical supplementation of low quality forages. For situations in which NPN is not a viable option, CRYSTALYX® offers several high quality all-natural protein supplements. No matter what your situation, CRYSTALYX® has a quality supplement for you. For more information, visit your local CRYSTALYX® dealer location or visit www.crystalyx.com.

CRYSTALYX<sup>®</sup> Brand supplements deliver NPN along with other essential nutrients in small regular doses which are ideal for rumen stimulation

CRYSTALYX® Brand supplements deliver NPN along with other essential nutrients in small regular doses which are ideal for rumen stimulation