A Comparative Study on Growth Performance, Body Composition, and Liver Tissue Metabolism Rearing on Soybean Lecithin-Enriched Artemia Nauplii and Microdiet in Rock Bream (Oplegnathus fasciatus) Larvae

This study is aimed at establishing optimal soybean lecithin (SL) enrichment protocols in Artemia nauplii and at comparing the growth performance, body composition, and liver tissue metabolism in rock bream (Oplegnathus fasciatus) larvae reared on SL-enriched Artemia nauplii or SL-enriched microdiet (MD). The enrichment protocol experiment results indicated 12 h enrichment, and 10 g SL/m(3) seawater could obtain desirable results. Rock bream larvae (25 days posthatching (dph)) were fed Artemia nauplii or MD for 30 days with three replicates. At stage 1 (larval 25-40 dph), significantly higher growth performance was observed in larvae fed the live prey (P<0.05). Conversely, at stage 2 (41-55 dph), feeding with MD significantly increased larval standard length, and specific growth rate compared with those of larvae fed live prey. Larvae fed a MD showed decreased lipolysis-related lipase activity as well as decreased amino acid catabolism-related alanine aminotransferase and aspartate aminotransferase enzyme activities in liver tissue. RNA sequencing revealed that feeding with the MD primarily increased the expression of lipogenesis-related genes and protein translation-related gene expression in the liver tissue. Notably, feeding with MD significantly increased ribosome biogenesis-related genes as well as mitochondria synthesis-related gene expression, indicating a high protein anabolism rate and high energy production in liver tissue. In conclusion, 10 g SL/m(3) seawater and 12 h could effectively enrich SL in Artemia nauplii. Retard weaning onto MD led to lower growth performance, which was likely due to the diversity of lipid and protein metabolism.

Automated summary

This study aimed to optimize the enrichment of soybean lecithin (SL) in Artemia nauplii and compare the growth, body composition, and liver metabolism of rock bream larvae fed SL-enriched Artemia nauplii or SL-enriched microdiet (MD). The results showed that 12-hour enrichment with 10 g SL/m(3) seawater yielded desirable results. At stage 1 (25-40 dph), larvae fed live prey exhibited significantly higher growth performance, while at stage 2 (41-55 dph), MD-fed larvae had increased length and growth rate. MD-fed larvae showed decreased lipolysis-related enzyme activity and liver amino acid catabolism-related enzyme activities. RNA sequencing revealed increased expression of lipogenesis and protein translation-related genes in the liver tissue of MD-fed larvae. The findings suggest that SL enrichment protocols and feeding strategies have significant effects on the growth and metabolism of rock bream larvae.