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Soybean Meal-Swinel Researchers at the University of Nebraska conducted two
experiments to determine the crude protein (CP) level below which nitrogen
retention and growth performance were reduced when low-protein, amino
acid (AA) supplemented, corn-soybean meal diets are fed growing swine.
The first experiment was a nitrogen balance study with gilts initially
weighing 41 kg and fed diets containing: 1) 18% CP; 2) 16% CP; 3) 14%
CP; 4) 14% CP plus AA; 5) 12% CP plus AA and 6) 10% CP plus AA. Lysine,
threonine, tryptophan and methionine were supplemented to equal the
levels in the diets containing four percent more protein. Nitrogen retention
was reduced (P>0.01) as the crude protein level of the diet was reduced
in both the standard and low-protein diets, but values were lower (P>0.01)
in the lower protein diets. In a growth study with gilts initially weighing
19.5 kg; the treatments were a 16% crude protein standard diet and low-protein
diets formulated to contain 15, 14, 13, 12 and 11% crude protein supplemented
with crystalline lysine tryptophan, threonine and methinione to equal
the total levels in the standard diet. The results showed minor differences
in performance of the pigs fed 12-16% crude protein diets. The pigs
fed the 11% crude protein diet had poor performance. Based on these
two studies, the researchers concluded that nitrogen balance is more
sensitive than growth to amino acid adequacy, and that other amino acids
(isoleucine and valine) may limit growth performance when protein levels
in rations are reduced by more than four percentage units. (Note-these
results support the concept that amino acid balance is important in
diets where crude protein levels are reduced). |
