The objective was to evaluate in vitro prediction of ileal digestibility of protein and amino acids (AA) for current nursery pig diets (n = 10) by using pepsin and pancreatin incubations. To compare in vivo ileal digestibility, forty nursery pigs (4 pigs per diet) with an initial BW of
kg were surgically equipped with T-cannula in the distal ileum. In all cases, the values of in vitro digestibility were higher than those of in vivo digestibility (p<0.05). With regard to the relationships of essential and non essential AA (CP), the
value was 0.76. With regard to AA, high relationships were observed in Ile, Thr, and Gly (0.85, 0.83, and 0.89, respectively). Also, there was a lower relationship for Arg, Met, Ala, Asp, Glu, Pro, Ser, and Tyr with
values of 0.56, 0.54, 0.40, 0.54, 0.45, 0.24, 0.49, and 0.35, respectively between in vitro and in vivo digestibility. The EAA relationship (
= 0.71) was generally higher than that of NEAA (
= 0.50) numerically. In conclusion, there were strong linear relationships between in vivo and in vitro ileal digestibility (CP, Ile, Thr, and Gly). In vitro prediction of ileal digestibility (CP, Ile, Thr, and Gly) seems to have significant potential for practical application.