Winter 2003
Producers may benefit from testing manure following a change in feed ingredients
by Wendy Powers, Department of Animal Science
As soybean meal costs continue to creep up, there is greater interest in incorporating crystalline amino acids into feed rations. While lysine use has expanded considerably in the last few years, incorporation of methionine has been much less wide spread. Economically, methionine is more attractive now than it has ever been, because of the rising cost of soybeans. Environmentally, there’s additional incentive to add both lysine and methionine into the feeding program.
Lysine and methionine are the first and second most limiting amino acids in corn-soy diets, meaning that they are the most deficient in the diet, relative to what the animal needs. By using crystalline amino acids, the animal’s requirements for lysine and methionine are met without overfeeding the remaining amino acids that are contained in the feed. The result is that less crude protein is fed to the animal. Much of the diet crude protein is from soybean meal so less soybean meal can be fed. Furthermore, if less excess protein is fed, then less excess nitrogen is consumed and therefore, less nitrogen is excreted in manure that has to be managed.
In recent research at Iowa State University, including lysine, alone, in swine diets resulted in a reduction of dietary crude protein from 17.4 percent to 17.0 percent. Adding lysine, methionine, threonine and tryptophan to the diet reduced crude protein content even further, to 14.5 percent.
Incorporation of lysine and methionine, though not tested in this study, would have resulted in a dietary crude protein content of approximately 16.2 percent. The reduced diet content does translate into less manure excretion. Urine nitrogen, where most of the nitrogen is excreted, decreased by 15 percent by adding the four amino acids. In addition, ammonia emissions were reduced by half. Others have demonstrated similar results. Similar results would be expected following feeding to poultry. However, data that addresses the combined use of lysine and methionine for poultry or swine is somewhat limited.
Nutrient excretion reductions will be site-specific based on how the amino acids are formulated in the diet and which amino acids are used. Producers who want to see how such practices affect their manure values should plan to test their manure before and after implementing such a change. If the change in diet formulation has already taken place, producers should still test their manure to see how composition in their manure storage facility compares to values used by a producer in his/her manure management plan. The change in nitrogen content may have a positive effect on manure management planning.
Information regarding manure sampling is available from Iowa State University Extension. Contact your ISU Extension county office for more information and ask about publication How to Sample Manure for Nutrient Analysis (PM 1558.) This publication can also be ordered from ISU Extension Distribution Center by calling (515) 294-5247 or downloaded from the Web at http://www.extension.iastate.edu/pubs/. The next issue of the Odor and Nutrient Management newsletter will feature information on manure sampling methods.
