TOO MUCH PROTEIN
BY MIKE MEHREN

I overheard a gentleman telling a friend that alfalfa hay had too much protein for beef cattle. Thank God for small favors! I think this myth may be related to bloat and calf scours that occurs when cattle are being fed alfalfa. Years ago, some believed that alfalfa and barley couldn’t be fed together without causing bloat. There is no doubt that this can happen, but it isn’t caused by excess protein.

Let’s look at how protein is used. Almost every feed has some protein. Part of the protein is attacked by the bugs in the paunch. This is called digestible intake protein (DIP). The remainder of the protein that escapes attack in the paunch is called undegradable intake protein (UIP). When the bugs in the paunch break down protein they convert it into their own cellular protein. This is composed of a certain group of amino acids (which are the building blocks of any protein). The animal swallows these bugs and digests and uses their proteins just like any other protein. This is very important to us and our animals because the animal can take grass, forbs, hays, and straws and simple nitrogen forms such as urea, biuret, and ammonia and make delicious tasting steak out of them.

The part of the protein that escapes attack by the microbes is digested directly by the animal. It breaks the protein down into its amino acids. This allows us to feed proteins that have a better amino acid profile than that of the bugs in the paunch. Feeds such as bloodmeal and fishmeal are examples of these feeds. Scientists working in the dairy industry have determined how much of certain amino acids the cows need to produce milk. If the diet doesn’t have enough of these amino acids, they incorporate them directly in the diet in a form that will escape the attack by the bugs. In the beef industry we are not only concerned with milk production; we are concerned with rate of gain, milk production, and fat deposition. That I know of, no one is feeding the paunch by-pass amino acids to beef cattle.

There are many situations where cattle are eating a high protein feed. Some examples might be:

Feed % Protein, dry matter
Cheatgrass, immature 17
Clover hay 21
Sudangrass, fresh 17
Turnip tops, fresh 16
Wheat pasture 20
Orchardgrass, fresh 18
Pea Vine Hay, irrigated 16
Alfalfa hay, 1/10 bloom 19

All of the above feeds have much more protein than a cow or a calf need, yet they don’t cause particular problems. It’s important to recognize that feeds with high protein have more energy, or TDN, than feeds with low protein. In other words, an orchardgrass hay with 16% protein will usually have more energy than an orchardgrass hay with 12% protein. This is important because animals don’t perform on protein alone; they must have energy, minerals, and vitamins in their diet. When an animal doesn’t have enough protein or energy in the diet, they begin to break down their own body tissues to supply these nutrients. They lose weight, and become more susceptible to disease and parasites.

Examples of TDN amounts with different levels of PROTEIN.

FEED
PROTEIN
TDN
 
........percent dry matter........
Alfalfa Hay, early bloom 19 59
Alfalfa Hay, mature 13 50
     
Grass Hay, immature 12 60
Grass Hay, mature 6 55
     
Grass Straw 4 40
Grass Straw Ammoniated 9 50


Note: Grass Seed Straw with ammoniation was used to show how protein and TDN can be improved on a very low quality feed. Ammoniation should only be used on low quality hay or straw. It could be used on the mature grass hay in the example above, but should not be used on the immature grass hay. For some reason when ammoniating high protein feeds, toxic compounds are formed. These are very dangerous to cattle.

Having extra protein, does allow us to use these feeds to supplement low protein forages such as straws and mature grass hays. I have sent many samples of mature bunchgrass to the lab for analysis. They usually come back with a protein value of 4 percent or less on a dry basis. Cows need about 7% protein in their diet before calving, so bunchgrass alone will not meet the protein needs of the cow. However feeding 5 lb of an 18% protein hay will bring the total ration up to 7%. A meadow hay having 6% protein will only need about 2.5 lb of a 16% hay to meet their needs. These figures apply to cows before calving. After calving the cow’s protein needs go up to about 12%, so more high protein hay needs to be fed to meet their needs.

Feeding the entire diet of a 19% alfalfa hay will hurt your pocketbook, not the animal. The excess protein will be used by bacteria and converted into energy to help the cow
gain weight or produce milk. Straight alfalfa can also be fed to heifers or old/thin cows that need to gain weight prior to calving. This may be the cheapest way to get the cattle to gain if prices for grain or grain by-product feeds are high. Sometimes hay is the only feedstuff that can be fed, there are no bunks or equipment to deliver any other kind of feed to cattle.

Occasionally you may run into a feed that has a much higher protein than expected. An example might be wheat or oat hay. We might expect a range of 12 to 14% protein, but the lab test came back showing a protein content of 20%. When this happened in the past, I asked the lab to re-test the sample to make sure the protein reported was accurate, not a sample error or a mathematical error. Following that, if the high protein test was repeated, I requested a nitrate test...and low and behold a high level of nitrate was found. Remember, a lab test for protein just tests the amount of nitrogen present. The nitrogen can come from sources other than protein. In that case we fed a little of the high-nitrate hay and a much greater amount of a low or no-nitrate high. Over a period of three weeks we gradually increased the high-nitrate hay and eventually fed nothing but that hay. The cattle had adapted to the nitrates in the same way that they adapt to urea or other non-protein-nitrogen compounds.

When comparing too little protein versus too much protein in a cattle diet, I’ll go with an excess of protein any day of the week. It may not be as efficient as a ration with the optimum amount of protein; however it is far better than not enough protein.

Michael J. Mehren, Ph.D. is a livestock nutritionist from Hermiston, OR. out in the feedlot searching for piles of economic stimuli. When he returns, he can be contacted by Email at mehrens@eotnet.net.

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