This study was conducted to determine and compare the apparent ileal digestibility and standardized ileal digestibility (
SID) of crude
protein (CP) and
amino acids (AA) in extruded full-fat soybean (EFSB) fed to nongestating, midgestating, late-gestating, and lactating sows. Six EFSB samples were collected from different sources. Fourteen nongestating sows (Landrace × Yorkshire; parity 3 to 5) were fitted with a T-
cannula at the distal ileum. After recovery, sows were assigned to a replicated 7 × 3 incomplete Latin square design. The diets included a
nitrogen-free (NF) diet and six experimental diets (EFSB 1 to 6). Eight midgestating sows (Landrace × Yorkshire; parity 3; day 48 of gestation), eight late-gestating sows (Landrace × Yorkshire; parity 3; day 90 of gestation), and eight lactating sows (Landrace × Yorkshire; parity 3; day 6 of lactation) were all assigned to four dietary treatments in a repeated 4 × 3 incomplete Latin square design. The diets included a NF diet and three experimental diets (EFSB 4 to 6). Results showed that there were significant differences in the AID and
SID of CP and other AA in nongestating sows (P < 0.05), the AID and
SID values of EFSB 1 to 3 were higher than those of EFSB 4 to 6, and the value of EFSB 5 was the lowest. For midgestating sows, there were differences in the AID of
methionine (EFSB 5 had a lower value than EFSB 4 and 6) (P < 0.01). For late-gestating sows, only the AID of
methionine (EFSB 5 had a lower value than EFSB 4 and 6),
tryptophan (EFSB 5 had a higher value than EFSB 4 and 6), and
proline (EFSB 5 had a higher value than EFSB 4) was different (P < 0.05), and the
SID of
methionine (EFSB 4 had a higher value than EFSB 5) and
tryptophan (EFSB 5 had a higher value than EFSB 4 and 6) was different (P < 0.05). The
SID of
histidine and
valine was greater in lactation than in nongestation (P = 0.045 and P = 0.02, respectively). The
SID of
isoleucine was greater in lactation than in nongestation and gestation (P < 0.01). The
SID of
methionine in nongestation was lower than in gestation and lactation (P < 0.01). The
SID of
cysteine was the lowest in midgestation (P = 0.045), and the
SID of
proline was greater in midgestation than in lactation and nongestation (P < 0.01). In conclusion, the AA ileal digestibility of six EFSB samples from different sources was different, and the ileal digestibility of CP and most AA was not affected by the physiological stage of sows.