Dietary supplementation with Lactobacillus reuteri XY227 and its impact on carcass traits, meat quality, and muscle fiber composition in finishing pigs

Probiotics are considered an important strategy for improving pork quality, although the mechanisms by which they influence muscle fiber type conversion and meat quality are not yet fully clarified.

Objective: This study evaluated the effects of Lactobacillus reuteri isolated from Ningxiang pigs on meat quality, amino acid composition, fatty acid profile, and muscle fiber type transition in finishing pigs.

Methods: Sixteen healthy castrated finishing pigs (Duroc × Landrace × Yorkshire, 63.36 ± 1.28 kg) were randomly assigned to two groups: a control group receiving a standard diet and a treatment group receiving the same diet supplemented with 0.4% (w/w) L. reuteri XY227 (1 × 10¹¹ CFU/kg) for 50 days. Carcass characteristics, meat quality parameters, muscle composition, gene expression, and muscle fiber distribution were evaluated.

Results: Supplementation with L. reuteri XY227 increased the Longissimus thoracis muscle area and lean meat yield. Improvements in meat quality were also observed, including higher meat redness and reduced lightness and shear force, indicating enhanced visual quality and tenderness. In terms of lipid composition, L. reuteri XY227 supplementation increased the concentrations of saturated, monounsaturated, and unsaturated fatty acids compared with the control group. In addition, higher levels of free amino acids, including isoleucine, leucine, and glycine, were detected in the Longissimus thoracis muscle. At the molecular level, dietary supplementation with L. reuteri XY227 increased the expression of genes involved in lipid metabolism and amino acid transport, including FABP4, SLC1A5, and SLC7A5. It also upregulated the expression of muscle fiber–related genes such as MyHCI and MyHCIIa, suggesting a modulation of muscle fiber type composition.

Conclusion: Lactobacillus reuteri XY227 enhances pork quality by modifying muscle fatty acid profiles and influencing muscle fiber type distribution in finishing pigs.