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That's the conclusion of Agricultural Research Service scientists who participated in a collaborative study, with 24 universities from north-central and southern regions of the United States, to evaluate the consistency of feed mixtures fed to swine.

The ARS Roman L. Hruska U.S. Meat Animal Research Center in Clay Center, Neb., along with university researchers, prepared the same corn-soybean meal diet, fortified with vitamins and minerals, at each location. Samples of each station's feed mixture were later analyzed for crude protein, calcium, phosphorus and zinc concentrations.

Laboratory analysis showed that although the diets were mixed uniformly, there was considerable variation in the nutrient concentrations at the 25 test locations. In other words, the diets mixed at some locations had higher levels of crude protein, calcium, phosphorus and zinc than those mixed at others.

Part of the variation in crude protein came from the corn and/or soybean meal that each location used. Differences in calcium and phosphorus contents could have been caused by various sources of supplemental dicalcium phosphate. Variation in zinc concentration was probably due to erroneous amounts of trace mineral premix added to the diet. Another reason for different results in calcium, phosphorus and zinc concentrations may have been that some laboratories do not routinely conduct mineral assays.

As a result of this study, published in the Journal of Animal Science, scientists and technicians should be careful when mixing test diets and should guard against drawing incorrect conclusions regarding dietary treatment effects. Accuracy in diet mixing is important when conducting animal nutrition research at multiple locations.

The mixed diets were not fed to pigs. The researchers mixed the diet only to test their hypothesis about the importance of accuracy of diet mixing

Source: USDA Agricultural Research Service, Agricultural Research Magazine - 18th July 2003