Dietary soybean lecithin inclusion promotes growth, development, and intestinal morphology of yellow drum (Nibea albiflora) larvae

Abstract

This study aimed to investigate the potential molecular mechanisms through which dietary soybean lecithin inclusion affects the growth, development, and intestinal morphology of yellow drum (Nibea albiflora) larvae. Four types of equal-protein and equal-lipid content microdiets (MDs) were formulated with graded levels of phospholipids (%, dry matter): 3.84 (SL0), 6.71 (SL4), 9.38 (SL8), and 12.21 (SL12). Larvae (25 days post-hatching; initial body weight 5.0 mg) were fed four replicates of MDs or Artemia nauplii (live prey) daily for 28 days. We found that dietary soybean lecithin inclusion promoted the growth performance, dorsal fin appearance rate, and body-color transition to juvenile-type in yellow drum larvae. Intestinal histological analysis confirmed that dietary supplementation with soybean lecithin prevented the appearance of vacuoles in enterocytes and increased the goblet cells as well as the perimeter ratio, muscular thickness, and mucosal fold height of the mid-intestinal tissue. Transmission and scanning electron microscopic analyses of the mid-intestine revealed that insufficient soybean lecithin inclusion decreased microvillus density and length and secretory vesicle production. Unique molecular identifier-RNA sequencing revealed that the improvement in intestinal morphology caused by dietary optimal soybean lecithin inclusion could be attributed to increased fatty acid β-oxidation and subsequent energy production in the intestinal tissue. Compared with the larvae fed with MDs, those fed with live prey experienced body-color transition retardation and a considerable fecal adhesion rate. The significantly decreased expression of genes encoding chemokines could attribute to the high fecal adhesion rate. Collectively, the findings of this study demonstrated the necessity of dietary soybean lecithin for the growth, development, and promotion of mid-intestinal morphology during the N. albiflora larval stage. The promotion of mid-intestinal morphology was likely caused by the resulting increased energy supply to enterocytes. Weaning larvae from live prey to MDs promoted intestinal health and development performance.