Novel Combination of Indicator Amino Acid Oxidation and Ileal Digestibility Methods in Growing Pigs to Assess Protein Quality of Cooked Millet

Abstract

Background

Millet is an important cereal grain, consumed by one-third of the world’s population. Hence, protein quality of millet needs urgent evaluation. The indicator amino acid oxidation (IAAO) method was combined with ileal digestibility for this purpose.

Objective

The objectives of this study were to determine the ileal digestibility of amino acids (AAs) in millet and to include the novel combination of the IAAO method to compare the metabolic availability (MA) of lysine in millet in growing pigs.

Methods

1) Standardized ileal digestibility (SID) of AAs were determined in cooked millet, in 6 ileal cannulated pigs assigned to 1 of 2 diets: hydrolyzed casein to establish endogenous losses, and a millet diet where the test ingredient was included at 65% as the sole protein source, in a replicated 3 × 3 Latin square design, 2) MA of lysine in cooked millet, was estimated in 8 pigs randomly allotted in a replicated balanced 4 × 4 Latin square design (4 diets and 4 collection periods). The MA of lysine was estimated by comparing the IAAO response to varying intakes of lysine in cooked millet, compared with IAAO response to L-lysine in the reference protein (crystalline AA) using slope-ratio analysis.

Results

The SID and MA of lysine in cooked millet were 83% and 96%, respectively.

Conclusions

To our knowledge, this is the first study to provide SID and IAAO estimates of MA in the same food assessed in the same pigs. The SID estimates are within ranges published by the National Research Council, and the IAAO-derived BA estimate for lysine is the same as previously published in humans. Thus, the IAAO method can be combined with SID in pigs to generate equations for correcting the dietary indispensable AA score.