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 (<i>Micropterus salmoides</i>). 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 <i>zo-1</i> and <i>occ</i> than the control group; the 9.53 mg/kg group showed significantly higher relative expressions of <i>il-10</i>, <i>tgf-β</i>, <i>igm</i>, and <i>cd83</i>, while <i>il-8</i> and <i>tnf-α</i> were notably lower, and <i>nf-κb</i> 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 <i>nrf2</i>, <i>cat</i>, <i>Cu-Zn sod</i>, and <i>gpx</i> 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.