Amino acid and phosphorus digestibility of fermented corn-soybean meal mixed feed with and fed to pigs

In the present study, a 2-stage solid-state fermentation process using followed by was performed with the purpose of improving the nutritional quality of corn and soybean meal (SBM) mixed feed (MF). The matrix of native MF and fermented MF (FMF) was analyzed using scanning electron microscopy to determine external structures after solid-state fermentation. Results of the present study indicated that the FMF had a greater concentration of CP and total P compared with the unfermented feed, whereas the contents of β-conglycinin, glycinin, phytate P, raffinose, stachyose, and NDF in FMF declined by 77.6, 86.7, 41.2, 47.2, 36.6, and 38.9%, respectively. The content of trichloroacetic acid-soluble protein, particularly those of small peptides and free AA, increased more than 3 times after fermentation. Scanning electron microscopy revealed that irregular shapes and a lot of porous structures were observed in the SBM of FMF, the cell wall of corn in FMF was destroyed, and the number of starch granules was decreased after 2-stage fermentation. Two animal experiments were conducted to evaluate the digestibility of CP and P in FMF when fed to pigs. In Exp. 1, 6 barrows (15.20 ± 1.27 kg initial BW) fitted with a T-cannula in the distal ileum were allotted to a replicated 3 × 3 Latin square with 3 diets and 3 periods per square. Two diets containing unfermented MF or FMF as the only source of protein and a N-free diet were formulated. Results indicated that the apparent ileal digestibility (AID) of total AA and Lys in FMF (74.98 and 75.34%) were greater ( < 0.05) than in untreated MF (69.66 and 68.56%). The standard ileal digestibility (SID) of Lys in FMF (82.17%) was also greater ( < 0.05) than in MF (75.91%). In Exp. 2, 16 barrows (17.57 ± 1.08 kg initial BW) were allotted to 2 diets formulated to contain MF or FMF as the sole source of P to determine the digestibility of P. The apparent total tract digestibility and standardized total tract digestibility of P in FMF were 58.14 and 64.72%, respectively. These values were greater ( < 0.01) than in untreated MF (37.11 and 44.89%, respectively). Our results indicate that a solid-state fermentation process using followed by offers an effective approach to improving the quality of corn and SBM MF.