Bacillus subtilis JATP-3 Improves Nitrogen Metabolism by Regulating Intestinal Flora and AKG in Weaned Piglets

Recently, it has been reported that oral probiotics improve the apparent digestibility of nitrogen in weaned piglets; however, the underlying mechanism is unclear. A total of 12 crossbred piglets (Yorkshire × Landrace; 28 days old) were randomly divided into two groups. The control (Con) group was fed with a basic diet + Luria-Bertani (LB; sterile; 10 mL), whereas the subject (Sub) group was fed with a basic diet + B. subtilis JATP-3 (1 × 10⁹ CFU/mL; 10 mL). The results showed that feeding B. subtilis JATP-3 increased the final body weight and nitrogen deposition rate of weaned piglets (P < 0.05); while the daily weight gain showed an upward trend (P < 0.1). The abundance of Pedicoccus, Collinella, Turiciator, Veillonella, Clostridium, and Escherichia were significantly increased in the jejunum (P < 0.05). The abundance of Olsenella and Pediococcus were significantly increased in the ileum (P < 0.05). The metabolomics analysis showed that the levels of l-lactic acid and Alpha-ketoglutaric acid (AKG) in portal vein plasma were significantly increased (P < 0.05). In addition, the content of AKG in muscle and liver increased significantly (P < 0.01). The metagenomics analysis showed that Veillonella encoded the functional genes of 2-oxoglutarate synthase and promoted AKG production. The protein expression of eIF4E-binding protein 1 (4EBP1) phosphorylated in the skeletal muscle increased (P < 0.05). In summary, B. subtilis JATP-3 promotes dietary nitrogen metabolism and skeletal muscle synthesis by modulating the intestinal microbiota and its metabolites, in which AKG may be one of the main mediators of the therapeutic effects of B. subtilis JATP-3.