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Title: VARIABILITY AMONG SOURCES AND LABORATORIES IN NUTRIENT ANALYSES OF CORN AND SOYBEAN MEAL

Author
item CROMWELL, G
item CALVERT, C
item CLINE, T
item CRENSHAW, J
item CRENSHAW, T
item EASTER, R
item EWAN, R
item HAMILTON, C
item Yen, Jong Tseng

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/1999
Publication Date: N/A
Citation: Cromwell, G.L., Calvert, C.C., Cline, T.R., Crenshaw, J.D., Crenshaw, T.D., Easter, R.A., Ewan, R.C., Hamilton, C.R., Hill, G.M., Lewis, A.J., Mahan, D.C., Miller, E.R., Nelssen, J.L., Pettigrew, J.E., Tribble, L.F., Veum, T.L., Yen, J.T. 1999. Variability among sources and laboratories in nutrient analyses of corn andsoybean meal. Journal of Animal Science. 77:3262-3273.

Interpretive Summary: Having a better understanding of, and a larger data base for, the nutrient composition of feedstuffs is important in order for nutritionists to formulate diets that will more precisely meet the nutrient requirements of pigs without having overages of nutrients (especially N and P), which are excreted in the manure and can become potential environmental pollutants. Accurate chemical analysis of feed ingredients is imperative for accurate and precise formulation of diets for swine and other food-producing animals. Unfortunately, some assays are difficult to perform and the results may vary from laboratory to laboratory as well as from assay to assay within the same laboratory. A cooperative research study involving members of a regional committee was conducted to assess the variability in nutrients composition (DM, CP, Ca, P, Se, amino acids) of corn and soybean meal from 16 sources and to assess the analytical variability in nutrient assays among 22 laboratories. The results of this study produces more accurate analytical information on corn and soybean meal, the two most commonly used feedstuffs in the swine industry. These new data have contributed to a major revision in many of the amino acid values for corn and soybean meal that are now currently listed in the 10th edition of the National Research Council's Nutrient Requirements of Swine. The study also shows that analytical variability can be quite large, and may be, for some assays, greater among labs than among sources of feedstuffs available for swine feeding. Finally, the data indicate that some labs perform chemical analyses more precisely (i.e., low within-lab variability) and accurately than other labs.

Technical Abstract: A cooperative research study involving members of a regional committee (North Central Regional Committee on Swine Nutrition [NCR-42]) was conducted to assess the variability in nutrient composition (DM, CP, Ca, P, Se, amino acids) of corn and soybean meal from 16 sources (15 states, mostly in the midwest [corn belt]) and to assess the analytical variability yin nutrient assays among 22 laboratories (labs; 16 experiment station labs and six commercial labs). Corn samples were obtained from the participating station's feed mill during 3 years (1989, 1990, 1992), as were soybean meal samples during 2 yeats (1989, 1990). Samples were analyzed for DM and CP by all labs, for Ca and P by 15 labs, for amino acids by 10 labs and for Se by six labs. Each lab used their own analytical procedures. Samples of corn and soybean meal varied in their nutrient composition depending on the area of origin. The greatest variation, as expected, was in Se concentration, ranging from .02 to .29 mg/kg in corn and .08 to .95 mg/kg in soybean meal. Crude protein and lysine in corn were positively correlated, but the regression coefficient was low. The relationship between CP and lysine for the two soybean meals combined was considerably stronger. Lysine in corn increased by .018 percentage point and lysine in soybean meal (regular and dehulled combined) increased by .063 percentage points for each 1 point increase in CP. Except for CP and Se, the analytical variability among labs was as great as, and in some cases greater than, the variability in nutrient composition among sources of corn and soybean meal. Within-lab analytical variability tended to be less than among-lab variability. Some labs performed analyses with considerably less variability and more accuracy than others.