Low-temperature two-stage probiotic fermentation enhances nutrition and safety of pig liquid feed.

Antinutritional factors present in complete feeds markedly diminish digestive and absorptive efficiency in animals, thereby affecting growth performance and resulting in economic losses. Liquid fermentation technology has been demonstrated to be an effective method of reducing antinutritional factors and enhancing the nutritional value of complete feeds. However, there is a lack of systematic research on the liquid fermentation and the screening of bacterial strains for use. In the present study, Bacillus subtilis and Lactobacillus plantarum characterized by excellent low-temperature tolerance, great enzyme activity, strong bacteriostatic capacity, and exceptional acid production, were evaluated for their suitability in a two-stage (aerobic followed by anaerobic) liquid fermentation process of complete pig feed. The results demonstrated that soybean antigenic protein and crude fiber underwent significant degradation, while crude protein and acid-soluble protein content exhibited significant increases in the feed following two-stage fermentation. Additionally, the accumulation of biogenic amines was inhibited to ensure the palatability of the feed. Furthermore, two-stage fermentation significantly enhanced the antioxidant and enzymatic activity of the feed. High-throughput 16S rRNA sequencing revealed an increased relative abundance of beneficial bacteria and a decreased abundance of pathogenic bacteria after fermentation. This study corroborated that a two-stage fermentation process could enhance the nutritional value, safety, and probiotic functionality of animal feeds. This finding provides a theoretical foundation for the development of functional fermented feeds and provides the necessary technical support for the practical application of liquid fermentation feeds. KEY POINTS: • Developed a novel low-temperature two-stage liquid fermentation feed strategy using Bacillus subtilis 3-16 and Lactobacillus plantarum E5 • Significantly degraded antinutritional factors and biogenic amines, while increasing the crude protein, acid-soluble protein, enzymatic activity, and antioxidant capacity of complete pig feed • Promoted beneficial microbiota dominance (e.g., Lactobacillus plantarum and Bacillus subtilis, while reducing pathogenic bacteria (e.g., Escherichia coli and Staphylococcus aureus).