Repeatability of Pig True Ileal Amino Acid Digestibility Coefficients: Among and Within Laboratories

When determining true ileal amino acid (AA) digestibility values in the growing pig to calculate digestible indispensable AA score, there are aspects of the protocol, both genetic and environmental, that vary between laboratories.

This study aimed to determine true ileal AA digestibility in 9 foods in each of 3 laboratories (Australasia, Europe, and North America) to determine interlaboratory variability. In each laboratory, 3 foods were also evaluated twice to determine intralaboratory variation.

Each laboratory followed a standardized protocol to determine true ileal AA digestibility for each food. Growing pigs received each food for 7 d and digesta were collected via a cannula at the terminal ileum on days 6 and 7. True ileal AA digestibility coefficients were determined for each food at each laboratory to evaluate interlaboratory variability. Three foods were evaluated twice in different cohorts of pigs at each laboratory (intralaboratory variation).

There was no statistically significant effect (P > 0.05) of the laboratory on the true ileal AA digestibility coefficients for 8 of the foods. Differences in AA digestibility were found for wheat bread. The mean coefficient of variation (CV) between laboratories for digestibility of the indispensable AAs was 5.0% with an overall mean for all AAs of 5.5%. For intralaboratory variability, there were no statistically significant differences (P > 0.05) in AA digestibility for any food with mean CVs for each AA within each of the 3 laboratories for the indispensable AAs of 1.3%, 1.1%, and 0.9%.

True ileal AA digestibility values determined in the growing pig for the same foods in different laboratories (interlaboratory variation) do not vary greatly. When a single food was evaluated a second time in the same laboratory, little variation among digestibility values was found.