The Significant Enhancing Effect of Vitamin B6-Fortified Feed on the Intestinal Digestive Efficiency, Immunity, and Antioxidant Defense Mechanisms of Juvenile Largemouth Bass (Micropterus salmoides)

A 12-week aquaculture trial was conducted to evaluate the effects of vitamin B6 on the intestinal health of largemouth bass (Micropterus salmoides). Six feeds with a vitamin B6 content of 2.03 (control group), 2.91, 3.30, 6.03, 9.53, and 21.79 mg/kg were prepared. The results were as follows. Regarding digestive efficiency, the 9.53 mg/kg group showed significantly higher activities of AMY, LPS, and TRY compared to the control group; the 6.03 mg/kg group exhibited increased AKP and Na+/K+ ATPase activities. Regarding immunity, the 6.03 mg/kg group had markedly higher relative expressions of zo-1 and occ than the control group; the 9.53 mg/kg group showed significantly higher relative expressions of il-10, tgf-β, igm, and cd83, while il-8 and tnf-α were notably lower, and nf-κb was noticeably decreased in 21.79 mg/kg group. For antioxidant capacity, the 6.03 mg/kg group had markedly higher activities of CAT, SOD, GSH-Px, and T-AOC levels, compared to the control group; the MDA level in the control group was markedly higher than in the other groups. The relative expressions of nrf2, cat, Cu-Zn sod, and gpx were highest in 9.53 mg/kg group and significantly higher than in the control group. In conclusion, an appropriate level of vitamin B6 in the feed is vital for protecting the intestinal health of largemouth bass.