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Reducing Protein in Swine Diets Two studies were conducted at Michigan State University
to determine the effect of reducing dietary protein on nitrogen utilization,
nitrogen excretion and amino acid digestibility in growing pigs. In
each study six barrows were allotted to one of six treatments in a Latin
Square design. The treatments consisted of four corn-soybean meal-based
diets containing 15, 12, 9, or 6% crude protein, a casein-based control
diet containing 15% crude protein and a protein-free diet. Crystalline
amino acids were added to the 12, 9, and 6% crude protein diets. The
indispensable to dispensable amino acid ratio was maintained at 45:55
with the addition of glutamic acid to the 9 and 6% crude protein diets.
The casein-based and protein-free diets were used to determine endogenous
total tract nitrogen and ileal amino acid losses. In the first study,
total nitrogen losses and nitrogen absorbed decreased linearly (P<0.001)
as the crude protein in the diet was reduced. Nitrogen retained as a
percentage of nitrogen intake and absorbed increased (P<0.001) as
the dietary crude protein was reduced from 15 to 6%. In the second study,
six barrows were fitted with a T-cannula at the terminal ileum to measure
amino acid digestibilities. For all dispensable and most indispensable
amino acids, the apparent and standardized ileal digestibility was increased
linearly (P<0.01) as the dietary crude protein level of the diet
was decreased. These results indicate that crude protein levels in growing
pig diets can be reduced from 15 to 12% with crystalline amino acid
supplementation without adversely affecting nitrogen retention. The
pig seems to compensate for the reduced crude protein by increases in
amino acid digestibilities. |
