UREA FOR CATTLE
Because of the price of protein, you may consider a supplement with urea in it this winter. Urea and the other non-protein nitrogen compounds, ammonium polyphosphate, and biuret get a lot of negative press, but are actually quite beneficial to cattle.
Urea actually factors into the place of grazing animals all over the earth. These wonderful animals can take simple nitrogen like urea and grass and convert it into nutritious protein that we can eat. The microbes that live in the paunch take the simple nitrogen and convert it into their own body protein, and when the animal swallows those microbes, it digests the protein just like any other source. You and I would starve to death if we had only these two feedstuffs to eat!
Urea is an organic compound that is present in nature. Animals remove the waste products of protein metabolism in the body through the kidneys in the form of urea. It is manufactured commercially by combining carbon dioxide and ammonia. Some natural beef programs don’t allow feeding urea, but as you can see the cattle themselves produce it, whether it is fed or not.
For comparison, let’s look at the amount of protein (or protein equivalent) in several feedstuffs.
When you look at the cost/lb of protein, it’s easy to see why urea should be considered if it can be fed and managed safely.
The non-protein content of
a supplement will always be shown on the label. An example would be:
You might assume that the supplement has 18% or 360 lb/ton of urea or other NPN source; but that’s not the case. Since urea is 282% protein equivalent, it only takes 127.7 lb/ton of urea to provide the 360 lb. of protein. The other NPN compounds have different protein equivalents, so each would require a different amount per ton.
Urea and other non-protein compounds can be toxic. However, salt, copper sulfate, and many plants can also be toxic. Whether it is toxic or safe depends on the amount consumed, how rapidly it is consumed, and the weight and age of the animal. Urea is not toxic to pigs or horses because they don’t have the enzymes to break it down. Urea isn’t fed to baby calves because their paunch isn’t functional.
Many people are leery of feeding urea because it may be toxic. However, in the past 30 years I know of only two incidents where it caused the death of cattle. One was a mixing error. A feedmill made a dairy concentrate and added 600 lb of urea in a ton instead of the 60 lb that was called for. The other incident involved a liquid supplement. A cold snap caused all of the water available to the cattle to freeze hard. The rancher did not get to the cattle for several days, and when he made it, there were some dead cattle lying quite near the liquid supplement feeder. It appeared that the cattle drank the liquid supplement to replace the water that was frozen. There was no snow for them to eat. In both instances, an unusually large amount of urea was consumed. If the correct amount of urea had been included or had the cattle not been forced to drink the liquid supplement for a source of water, there would have been no problem. Years ago, many cattle deaths were blamed on urea, just because it was in the supplement, however there is a very definitive protocol that can be used to determine whether urea is at fault. The biggest issue with urea is getting the right amount to the cattle at the right time and circumstances. Almost all finishing feedlots have urea in their protein supplement. In a high-energy finishing ration the urea is used very effectively.
Now down to specifics. Most of the information on low quality forage and supplements for wintering cows comes from parts of the country that graze warm season and cool season grasses. It turns out that cattle respond differently to these kinds of grasses. Cool-season grasses grow early in the spring and go dormant during the hot weather. They may begin to grow again when the weather cools if there is enough moisture (fall green-up). Our range grasses are predominantly cool-season. Warm-season grasses begin to grow later in the spring and continue to grow through hot weather. They go dormant when the weather cools down. When a low-protein warm season grass is supplemented with protein, intake and digestibility of the grass increases very dramatically. This does not appear to be the case for cool-season grasses.
Dr. D. Bohnert of the Eastern Or Ag Res Station in Burns reviewed all of the studies comparing vegetable protein versus urea (NPN) protein supplements for cool-season grasses, only 9% of the studies reported an advantage to feeding vegetable protein. This information shocked me! I have assumed that vegetable protein was far superior to urea protein when supplementing low quality forage. When in fact, urea protein is used efficiently when a cool-season grass has less than 6% protein and less than 54% TDN. The figures 6% protein and 54% TDN describe most of our native bunch grass and virtually all of the straw that is commonly fed in the Pacific Northwest. When soybean meal was compared with urea using cow body condition as the measure of performance; both were very similar. It should be noted that this is not the case when the forage has 7% or more crude protein and more than 54% TDN. In that instance, vegetable protein is far superior as a source of protein.
What about cost? Say we have two supplements that both have 32% crude protein, however one has mostly NPN protein while the other has all vegetable protein. All other parts of these supplements are as similar as possible for TDN, minerals, and vitamins.
Figures for prices taken from table above.
This shows that the protein portion of the supplement costs much more for the soybean meal protein supplement versus the urea-soybean meal supplement. This would certainly encourage me to consider high NPN supplements for wintering cows on low protein forages. NPN protein supplements are best fed daily rather than 2 or 3 times each week. Any self-fed supplement such as a liquid, block, or meal having urea should be eaten daily under normal circumstances.
If you happen to have read my column on phosphorus, it may be noted that huge savings may be made if the needed amount of phosphorus is purchased rather than just buying the same product year in and year out. The phosphorus in the protein supplement can also be matched to your cattle needs. Using urea to supply some of your supplemental protein can result in a savings of $.03/head/day at 1 lb intake.
Mehren’s politically incorrect dictionary defines Obamanable as a type of Medieval Snowman capable of Obamation of the critters in the forest.
Michael J. Mehren, Ph.D. is a livestock nutritionist roaming the desert in search of the illusive cheap feed near Hermiston, Oregon. He can be reached by email at firstname.lastname@example.org.