Effects of dietary proline on growth,physiology, biochemistry and TOR pathway-related gene expression in juvenile spotted drum Nibea diacanthus

Fisheries Science - Amino acids can act as signaling molecules in protein synthesis and animal growth by regulating several genes in the target of rapamycin (TOR) pathway. An 8-week feeding trial...     

Effect of hydroxyproline supplementation on growth performance,body composition,amino acid profiles,blood‐biochemistry and collagen synthesis of juvenile chu's croaker (Nibea coibor)

Hydroxyproline (Hyp) may play an important role in collagen metabolism, as it is almost exclusively found in collagen. To examine this possibility, a 56‐day feeding trial was conducted to evaluate the effect of graded supplementaries of Hyp (0, 2.5, 5, 7.5, 10 and 12.5 g/kg dry diet weight) on growth performance, feed utilization, biochemical composition and collagen synthesis of chu's croaker, Nibea coibor (13.6 ± 0.28 g). The growth performance and feed utilization were improved with increased levels of dietary Hyp, reaching a maximum at 5 g/kg (diet H2) followed by a slight decrease. Polynomial regression analysis showed that the maximum specific growth rate (SGR) was attained at 7.177 g/kg dietary Hyp. Increasing levels of Hyp did not affect body composition of juvenile Nibea coibor. However, dietary Hyp supplementation significantly affected the levels of Leu, Ile, Met, Lys, Ser, Glu and Pro in muscle and the levels of Met, Lys, Glu, Pro and Gly in swim bladder. The serum calcium (SC) level decreased significantly with increasing levels of dietary Hyp. However, the triglycerides (TG) and total cholesterol (T‐CH) levels in serum and liver were relatively stable. Importantly, the acid‐soluble collagen (ASC) and total collagen (TC) levels in swim bladder increased significantly initially and then decreased after reaching a maximum. Polynomial regression analysis revealed that the maximum TC level in swim bladder was attained at 9.736 g/kg of dietary Hyp. Collectively, these results suggest that the appropriate provision of hydroxyproline is essential for maximal collagen synthesis and growth.     

Formulated diet alters gut microbiota compositions in marine fish Nibea coibor and Nibea diacanthus

Nibea, an economical marine fish, is generally fed on trash fish (the low‐value fish), which can cause high feed costs and waste pollutions in high‐density aquaculture. To assess the effect of formulated diet on the gut microbiota in Nibea coibor and Nibea diacanthus, denaturing gradient gel electrophoresis, clone libraries analysis and Illumina sequencing of the 16S ribosomal RNA gene were used in this study. Two Nibea fishes were both dominated by Gammaproteobacteria (especially Photobacterium) and shared a set of gut microbiota, including Bacilli, Mollicutes, Alphaproteobacteria and Fusobacteriia. Statistical analyses revealed that formulated diet led to lower feed conversion ratio (p < 0.001), lower abundance of Vibrio (p = 0.040) and infectious diseases pathways (p = 0.001), higher abundance of polysaccharide‐degrading bacterium Cellvibrio (p = 0.006) in two Nibea species, with higher weight gain rate (p = 0.023) and microbial diversity (Shannon, p = 0.049 and Simpson, p = 0.044) and more carbohydrate metabolism (p = 0.020) observed in N. coibor. The distribution and correlation network of 17 potential short‐chain fatty acid producing bacteria were obtained and visualized in all treatment groups. The results reveal that formulated diet has beneficial effects on the gut microbial ecology in two Nibea fishes, which suggests the possibility of replacing trash fish diet with formulated diet in Nibea aquaculture.