Pig True Ileal Digestible Amino Acid Contents of Individual Ingredients are Additive in Mixed Meals and Allow Accurate Predictions of Digestible Indispensable Amino Acid Score Values

Background

Although not every food protein contributes sufficient quantities of all of the indispensable amino acids (AAs) required for human health, the human diet is a mixture of foods. It is therefore important to evaluate protein quality in mixed meals.

Objectives

The hypothesis was that the true ileal digestible AA content of mixed meals can be predicted from the amounts of digestible AA determined for individual food ingredients, allowing further prediction of the digestible indispensable amino acid score (DIAAS) for meals.

Methods

Four diets contained either pea protein isolate (PPI), whey protein concentrate (WPC), or mixtures of PPI:WPC at a ratio of 25:75 (PP25) or 75:25 (PP75). Six ileal cannulated pigs were allocated to a 4 × 6 Latin Square design. Experimental diets at 10% protein and a protein-free diet were fed for 7 d with ileal digesta collection on days 6 and 7. True ileal digestibility (TID) of AA, amount of digestible AA, and DIAAS were calculated for each diet and predicted for the 2 mixed meals.

Results

Predicted and determined digestible AA contents of the mixed diets were not different. The predicted values fell within the confidence interval (95%) of the determined values. DIAAS for PPI was 61% and for WPC it was 96%. DIAAS calculated based on the predicted amounts of digestible AA for PP25 was 104% and for PP75 83%. These values were nearly identical to the determined values of 104% and 84% for PP25 and PP75, respectively.

Conclusions

The amount of digestible AA and DIAAS can be accurately predicted in mixtures of PP and WPC from the AA digestibility values for the individual ingredients.