Effects of Bacillus amyloliquefaciens- and Bacillus licheniformis-Fermented Feeds on Performance, Meat Quality and Gut Microbiot of Fattening Pigs

This study aimed to evaluate the nutritional composition and fermentation quality of feed fermented by Bacillus amyloliquefaciens and Bacillus licheniformis as well as their effects on growth performance, meat quality, blood parameters, and gut microbiota in fattening pigs. A total of 72 healthy Duroc × Landrace × Large White crossbred barrows (68.78 ± 1.41 kg, p > 0.05 for initial body weight among groups) were randomly assigned to three dietary treatments, with four replicates pens per treatment and six pigs per pen. The pigs were fed one of three diets: (1) CK: 100% basal diet; (2) YR1: 50% basal diet + 50% feed fermented with Bacillus amyloliquefaciens YR3.2; and (3) YR2: 50% basal diet + 50% feed fermented with Bacillus licheniformis YR3.1. The experiment consisted of a 7-day adaptation period and a 50-day treatment period. The results showed that the crude protein, starch, lactic acid, acetic acid, and propionic acid contents were significantly higher in the treatment groups than in the control group (p < 0.05). The final body weight of fattening pigs, serum superoxide dismutase activity, and redness value of the longissimus dorsi muscle were significantly higher in the treatment groups than in the control group (p < 0.05). The carcass weight of the YR1 group was significantly higher than that of the other groups (p < 0.05). Moreover, the shear force of pork was significantly lower in the treatment groups than in the control group (p < 0.05). Microbial analysis showed that Firmicutes dominated the jejunum and cecum in all groups (>80%). In the YR1 group, the abundance of Clostridium increased in the jejunum, whereas the abundance of Terrisporobacter decreased. In the YR2 group, the abundances of both Clostridium and Terrisporobacter increased in the jejunum and cecum. In conclusion, fermented feed prepared with Bacillus amyloliquefaciens and Bacillus licheniformis has a positive effect on the growth performance of fattening pigs, but fermented feed prepared by Bacillus amyloliquefaciens YR3.2 has a more significant effect on improving growth performance, feed conversion efficiency and some meat quality indicators.