Effect of inclusion of animal proteins to plant protein-based diet on physiological condition of red seabream Pagrus major.

This study investigated the physiological effects of incorporating animal protein into a plant protein-based diet for red seabream, Pagrus major. Four diets with different levels of protein ingredients were formulated and fed to the fish (initial body weight: 11.3 ± 0.1 g) over a 4-week trial: a fishmeal (FM)-based diet (FM diet); an FM-free high-plant/low-animal protein diet (HPLA diet); an FM-free medium-plant/medium-animal protein diet (MPMA diet); and an FM-free plant protein-based diet (P diet). Fish fed the P diet showed an inferior growth performance, abnormal hindgut morphology, increased cholesterol biosynthesis, suppressed bile acid synthesis, and stimulated glycine and glutathione metabolism. These unfavorable effects on cholesterol metabolism were also confirmed by comprehensive transcriptome analysis. In addition, fish fed the P diet showed an upregulated expression of the haptoglobin precursor, an indicator of red blood cell damage. All of these negative physiological effects were either partially or totally improved by supplementation of the diet with animal proteins. Expression levels of insulin-like growth factor binding protein 1, a negative indicator of growth, were higher in fish fed the HPLA and P diets compared to fish in the FM group, whereas those of fish fed the MPMA diet were comparable to those of fish in the FM group. These results suggest that an optimal combination of plant- and animal-protein sources could improve the physiological condition of red seabream. Optimization of the dietary levels of plant and animal protein ingredients would contribute to the development of a low fishmeal diet that is well suited to improving the physiological condition of aquaculture target species. [ABSTRACT FROM AUTHOR]