Determination of Digestible Indispensable Amino Acid Scores for Plant Proteins and Skim Milk Powder Measured in Pigs

The objective was to determine the digestible indispensable amino acid score (DIAAS) of food sources using the pig model and in vitro procedures. The standardized ileal digestibility (SID) of amino acids (AA) in white rice, wheat, pea protein concentrate (PPC), soy protein isolate (SPI), and skim milk powder (SMP) were determined in pigs. Twelve barrows with an initial body weight of 28.4 kg (standard deviation = 4.0) equipped with a T-cannula at the distal ileum were allotted to a replicated 6 x 5 incomplete Latin square design with six diets and five periods. Five experimental diets contained each ingredient as the only source of AA. Additionally, a nitrogen-free diet was prepared to measure the basal endogenous losses of AA for the calculation of the SID of AA. The in vitro ileal disappearance (IVID) of crude protein (CP) in the five food sources was also determined using the conventional flask procedure and the multi-sample simultaneous in vitro procedure employing the Daisy(II) incubator. The DIAAS values for white rice were 42, 50, and 60 for infants, children, and adults, respectively. For wheat, the DIAAS values were 46, 56, and 66, respectively. The DIAAS values for PPC were 47, 58, and 69 for infants, children, and adults, respectively. For SPI, the values were 61, 74, and 87, respectively. The DIAAS for SMP were 82, 112, and 131 for infants, children, and adults respectively. The IVID of CP in SMP was greater (p < 0.05) than that in other sources. The DIAAS calculated based on IVID of CP were similar to those determined based on the SID of AA in pigs. In conclusion, white rice, wheat, pea protein concentrate, and soy protein isolate were observed to have DIAAS values less than 100, indicating that these ingredients need to be combined with other protein sources to meet the indispensable AA requirements. Skim milk powder had a DIAAS greater than 100 for children and adults.