Digestibility of crude protein and amino acids in corn grains from different origins for pigs

• We determined ileal digestibility of amino acids in various corn sources for pigs.
• The amino acid contents varied among corn sources from different origins.
• The standardized digestibility of most amino acids was similar among corn sources.
• The digestibility of lysine was variable among corn sources.

This experiment was conducted to determine the coefficients of ileal apparent (CIAD) and standardized digestibility (CISD) of crude protein (CP) and amino acids (AA) in corn sources from different origins for pigs. The corn sources included yellow corn from the United States (n = 5; USY), yellow corn from South Africa (n = 2; SAY), and white corn from South Africa (n = 2; SAW). Nine diets were prepared to contain each corn source at 947 g/kg as the sole source of CP and AA. A nitrogen-free diet was also prepared and used to measure basal endogenous losses of CP and AA. Ten boars with an initial body weight of 52.2 ± 9.0 kg were surgically fitted with a T-cannula in the distal ileum and were allotted to a 10×10 Latin square design with 10 diets and 10 periods. Each period consisted of 3-day adaptation and 2-day sample collection periods. Results indicated that the concentrations of CP and AA varied among corn sources from different origins, and those of lysine and tryptophan had coefficient of variation of 16.3 and 24.0%, respectively. Significant differences were observed (P<0.05) for the CIAD of CP and AA (arginine, histidine, lysine, tryptophan, aspartic acid, cysteine, glycine, and proline) among the nine corn sources. The CIAD values of most AA except for six AA (isoleucine, leucine, phenylalanine, tryptophan, proline, and tyrosine) were greater (P<0.05) for SAY than those for USY. The CISD values of CP and most AA were similar among corn sources. However, the CISD of lysine was different (P=0.017) among the nine corn sources in the range of 0.611–0.765. The CISD of lysine for SAY (0.747) was greater (P<0.001) than that for USY (0.655). In conclusion, the CIAD values of CP and most AA in corn varied among corn sources from different origins, but the CISD values of AA except lysine were relatively similar among corn sources with varying concentrations of CP and AA. Further research is required to identify the reasons for the variability in the CISD of lysine among corn sources from different origins and to search for a method to reduce variability.