Diets May Actually Be Different
July 18, 2003
Swine that are fed the same diet in
different locations don't always get the same level of nutrients. 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
ARS is the U.S. Department of
Agriculture's chief scientific research agency.