Ileal amino acid digestibility, and the endogenous enzyme activities in cannulated early growing pig fed soybean meal diets supplemented with β-mannanase

Objective: This study evaluated the effects of dietary β-mannanase supplementation on apparent and standardized ileal amino acid (AA) digestibility, endogenous digestive enzyme activity, and digesta viscosity in early growing pigs.Methods: Five 49-day-old LYD intact male pigs (20.25 ± 0.33 kg body weight) were surgically fitted with distal ileum T-cannula.Following a 14-day recovery and 4-day adaptation, ileal digesta was collected and stored at -20 ℃ for further analyses.One pig was assigned a nitrogen-free diet; the remaining four pigs were assigned to two dietary treatments in a Latin square design: a control diet without β-mannanase (MS-) and a diet supplemented with 0.05% β-mannanase (MS+; 400 U/kg feed).Results: MS+ significantly increased dry matter (DM) and crude protein (CP) digestibility (p<0.05), with a tendency toward higher organic matter digestibility (p=0.063).The apparent and standardized ileal digestibility (SID) of arginine, lysine, and threonine were significantly higher (p<0.05) in the MS+ group, with tendencies toward greater SID of isoleucine (p=0.066),proline (p=0.076), and tyrosine (p=0.062).Activities of trypsin, protease, and amylase were greater (p<0.05) in MS+ pigs.Additionally, MS+ reduced jejunal digesta viscosity (p<0.05) and tended to reduce fecal viscosity (p=0.074).Correlation analysis indicated that jejunal and fecal viscosities were negatively associated with DM and CP digestibility and the SID of tryptophan and valine.Conversely, trypsin and protease activities exhibited strong positive correlations with CP digestibility and the SID of valine, while amylase activity was positively tied to DM digestibility.Conclusion: Dietary supplementation with 0.05% β-mannanase (400 U/kg) in early growing pigs significantly improves the apparent ileal digestibility of dry matter and crude protein, as well as the standardized ileal digestibility of arginine, lysine, and threonine, by inducing a 25.0% reduction in jejunal viscosity that facilitates enzyme-substrate interactions and stimulates endogenous digestive enzyme secretion.