Interpretive Summary: The direct and difference procedures result in similar estimates for amino acid digestibility in feed ingredients fed to growing pigs
By Anne Zinn
A recent study published in the Journal of Animal Science tested the hypothesis that values for standardized ileal digestibility (SID) of amino acids (AA) in corn, wheat, and wheat middlings obtained using the direct procedure in diet formulation for growing pigs are not different from values obtained using the difference procedure. Values for the SID of AA are often used as additives in the mixed diet formulation for pigs. Currently, data that compare the two procedures to calculate SID of AA for the same ingredient have not yet been reported. This comparison is important because there can be negative side effects, such as reduced growth (seen with the direct procedure) and greater standard errors (seen with the difference procedure). Results of this study indicate that the SID of indispensable AA in corn, wheat, and wheat middlings can be determined by either the direct or difference procedure without influencing results. This means there is no reason to be concerned about AA being included below the requirement as is the case when the direct procedure is used to estimate SID of AA in cereal grains and grain co-products. In this experiment, there was no advantage to using the difference procedure, but because of greater standard errors, more replicates are needed to obtain a certain power of the experiment if the difference procedure is used over the direct procedure.
The full paper will be available soon on the Journal of Animal Science website.