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Opinions and comments by: James I. Sprague, Livestock Nutritionist Requirement vs. Environmental Concerns The latest beef feedlot research at universities is focused on the interaction of (1) the requirement for optimum production and (2) a concerted effort to reduce the nitrogen in manure. There are two reasons for extra nitrogen in manure. We sometimes (1) feed more protein than the requirement and (2) feedlot cattle are not very efficient utilizers of protein. New words are now being used by researchers and nutritionists, such as metabolizable protein, undegraded feed protein (by-pass protein), rumen degradable feed protein, and soluble feed protein. Metabolizable protein will be the scientific method to express the protein requirements of beef and dairy cattle. Metabolizable protein is a calculated value from the ingredients and needs for maintenance, lactation and gain. Crude Protein Will Still be Specified Crude protein content will still be specified for feedlot rations and supplements. Crude protein is still the practical way to express the protein content for quality control work. New Protein and NPN (Non Protein Nitrogen) Research are Under Way Research is under way by a consortium of universities, according to Glen Duff, formerly at New Mexico State University's Clayton station. The research will be completed by USDA-ARS Bushland, Texas, West Texas State University, and Texas Tech University, in cooperation with the Texas Diagnostic Laboratory. At New Mexico, they have compared a natural supplement with cottonseed meal as the source of the protein supplement, compared to a supplement with all urea, and a program with 50 percent urea and 50 percent from cottonseed meal. Dr. Duff says his research will be presented with the combined experiments. Duff is now at the University of Arizona. His new phone number is 520-626-5573. The results of this research will be closely observed by nutritionists and the cattle industry. Protein Changes with the Age of Cattle Nutritionists know that the requirement for protein changes with the age of the animal and the growth program. But in feedlots we run cattle finishing factories, so our practical rations are usually starting rations, growing rations, "step-up" and finishing rations. It would be ideal to have several finish rations to adjust the protein to the desired requirement. This may save a small amount of money in supplement cost and may result in less nitrogen in the manure. Livestock nutritionist use several factors in designing the protein and NPN content of rations. Percentage Rations For material handling, nutritional, and feed additive reasons the industry has changed to percentage rations. Percentage rations are much better for accounting the feed to each pen to generate financial records. However, this system does not allow cattle feeders to take advantage of special requirements of certain pens of cattle. The result, we over-formulate for the older cattle and under-formulate for the young growthy cattle. Feeding a Specific Amount of Supplement Per Head Per Day Farmer feeders often feed their protein and additive supplements in increments of two to three pounds per day. For youthful cattle, this program resulted in the supplement being a large percent of the ration. And then as the cattle became older and begin to eat more feed, the percent of the ration becomes smaller. This system is a practical way to program the supplement to decreasing protein requirements as the feed intake increases. The down side of this program is that each pen must be fed separately. Consequently for material handling and feed additive reasons, most feeders have changed to percentage rations. Percentage rations are preferred for the ionophore additives like Rumensin and Bovatec. Higher Protein with High Energy Rations The industry recognizes that as the energy of rations is increased and feed intake is reduced , it will result in a need for a higher protein percent of a ration. Proper protein feeding is particularly critical for growthy cattle and possibly extra protein is needed for an aggressive implant program. NPN Amount, All or None, or Part NPN It is well known by cattle people and their nutritionist that a large amount of the supplemental protein can come from added NPN sources like urea. The rumen bacterial breakdown the natural crude protein, urea, and ammonium sulfate in the ration to ammonia in the rumen. The rumen bugs then use this to produce bacterial protein which is a high quality protein digested in the lower gut. The amount of NPN specified by nutritionists depends on the ration ingredients and the energy of the ration. Nutritionist are beginning to consider the NPN like material in fermented feeds such as silages and high moisture grain. We test for water soluble protein in the silage of our clients to help determine the amount of NPN that can be added. A large amount of the crude protein in silages is soluble and some of the crude protein (NPN like material) may not be available to the rumen bugs or digested in the small intestine. The new metabolizable protein method helps address this problem. Many nutritionist still supply only a portion of the protein in the ration from NPN because it is believed cattle performance factors are maximized. Yet, because of economics, urea is substituted for as much as possible of the supplemental protein in most feedlot programs. But all natural protein supplemental programs, with no urea, are still successfully used by some feeders. There is enough rumen degradable protein from soybean meal, cottonseed meal and other plant protein sources to feed the rumen bugs. © |
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