Studies were conducted to demonstrate the effects of L L-alanyl-L L-glutamine (L-AG) on the growth performance and physiological function of hybrid sturgeon Acipenser schrenckii $ · Acipenser baerii # larvae. Five isonitrogenous experimental diets contained five different L-AG levels: 0.0, 0.25, 0.5, 0.75 and 1.0%. Triplicate groups of 1500 fish (mean weight 0.42 ± 0.05 g) were stocked in each aquarium (220 L), which were connected to a recycling system and fed to apparent satiation for 56 days. When the culture experiment was terminated, weight gain, specific growth, survival and condition factor were determined and served as indices for assessing growth performance. Na + -K + ATPase, glutamine, superoxide dismutase (SOD), malondialdehyde (MDA), protease, lipase and amylase of the whole fish or intestine were also determined. The results showed that the growth performance improved significantly with increasing dietary L-AG supplementation levels from 0.0 to 1.0%. Fish fed diets containing higher L-AG level had greater Na + -K + ATPase, glutamine, SOD and lower MDA when the supplementation level increased. Compared to the control group, however, there were no significant differences in protease, lipase or amylase of the intestine. In conclusion, dietary L-AG supplementation could help improving growth performance and physiological function of larval hybrid sturgeon.

In this study, the effects of arginine on growth, serum antioxidant levels, intestinal digestion physiology, intestinal protein synthesis, and expression of inflammatory-related genes of triploid juvenile rainbow trout (Oncorhynchus mykiss) were investigated. Five diets containing 0.86%, 1.65%, 2.10%, 2.85%, and 3.50% arginine were fed to satiation to triplicate groups of 30 fish per tank for 8 weeks. The results showed that the weight gain rate, specific growth rate, and protein efficiency ratio significantly increased. The optimal dietary arginine requirement was 2.48% (5.97% of dietary protein) based on quadratic regression analysis between specific growth rate and dietary arginine content. There were no significant differences in crude lipid and ash content. Moisture significantly decreased, and crude protein content significantly increased ( P < 0.05 ). Superoxide dismutase, catalase, and lysozyme levels in serum and the liver first significantly increased and then decreased with the level of arginine compared to the control group ( P < 0.05 ), while the malondialdehyde level significantly decreased. Intestinal lipase and amylase levels significantly increased, but there was no significant difference in trypsin level ( P > 0.05 ). The muscular layer thickness and villus width foregut in the 2.85% group were significantly increased. TOR at 2.86% and IGF-1 and S6K1 at 2.11% reached the maximum level, and IL-1β, IL-6, and IL-8 showed a decreasing trend with their lowest levels in the 3.50% and 2.85% groups. The expression of TNF-α first decreased and then increased with the arginine level. Both TGF-β and IL-10 expression first decreased and then increased with the level of arginine and reached the maximum value in the 2.85% group. NF-κB showed an opposite trend and reached the lowest value in the 3.50% group. In conclusion, dietary arginine has a significant effect on growth, serum antioxidant capability, digestion physiology, immunity, digestion, and absorption of nutrients in triploid O. mykiss, and the optimum requirement is 2.48% fed a low-fishmeal diet.

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A study was conducted to compare growth and nutrients in the muscle of diploid and triploid masu salmon (Oncorhynchus masou B., 1856). Triploidy was induced by providing a heat shock treatment to the fertilized eggs. When fish grew up to 100 g around, triploids were prepared after triploidy determination prior to the trial. Initial mean weights of diploids and triploids were 103.67 ± 9.66 g and 109.95 ± 8.45 g, respectively. Quadruplicate groups of 30 fish were randomly assigned in each tank fed by water with a flow-through system and were fed to apparent satiation for 140 days. Survival, specific growth rate, feed conversion rate, condition factor, relative growth rate and absolute growth rate were determined in both groups. The contents of moisture, crude protein, lipid, ash, amino acids and fatty acids in muscle were analyzed. It has been determined that the triploid fish showed a higher weight gain than diploid fish despite the difference was not significant (P>0.05). There were no significant differences in crude protein, crude lipid, ash, amino acids and fatty acids between diploids and triploids (P>0.05). In conclusion, growth performances and nutritional composition in muscle were similar between diploids and triploids, and triploids had no negative effects on muscle nutrients under fish farming practices especially for the production of Oncorhynchus masou on-growing stages.

This study estimated the effect of substituting fishmeal completely with cottonseed protein concentrate (CPC) in the diet of sturgeon (Acipenser schrenckii) on growth, digestive physiology, and hepatic gene expression. A control diet containing fishmeal and an experimental diet based on CPC was designed. The study was conducted for 56 days in indoor recirculating aquaculture systems. The results showed that weight gain, feed efficiency, and whole-body essential amino acids (EAAs) all decreased significantly in the experimental group, while whole-body non-essential amino acids (NEAAs) and serum transaminase activity increased (p < 0.05). The activity of digestive enzymes in the mid-intestine was significantly reduced (p < 0.05), and liver histology revealed fatty infiltration of hepatocytes. The hepatic transcriptome revealed an upregulation of genes linked to metabolism, including steroid biosynthesis, pyruvate metabolism, fatty acid metabolism, and amino acid biosynthesis. These findings indicate that fully replacing fishmeal with CPC harms A. schrenckii growth and physiology. This study provides valuable data for the development of improved aquafeeds and the use of molecular methods to evaluate the diet performance of sturgeon.

A study was conducted to compare growth and survival of Hucho taimen larvae from 21 to 76 days after hatch (DAH) fed one of three diets: formulated feed alone (group F); a co-feeding diet of water fleas, tubifex and formulated feed (group C); or live food of water fleas and tubifex (group L), and to investigate the potential use of dietary L-alanyl-L-glutamine (L-AG) in larval taimen for a more nutritious starter diet. Triplicate groups of 5000 fish were randomly assigned to each aquarium provided with water from a flow-through system, and fed to apparent satiation. The results show that larvae can feed efficiently on floating crumbled particles of formulated feed. Weight gain of larvae fed only formulated feed was significantly lower than other groups at 34 DAH (P < 0.05). At the end of the experiment, weight gain reached the highest value in group F and was lowest in group L (P < 0.05). Condition factor reached the highest values in group F and lowest in group C (P < 0.05). Specific growth rate was in accordance with weight gain at 76 DAH. Survival showed no differences among the groups (P > 0.05). In conclusion, H. taimen larvae can be fed formulated feed alone and L-AG may be used as a feeding attractant during the weaning process, which should lead to a better understanding in the rearing improvement in the feeding of larvae.

To investigate the effect of dietary L-Alanyl-L-glutamine (Ala-Gln) supplementation on Amur sturgeon, Acipenser schrenckii, 180 healthy fish (initial body weight 21.23 ± 0.17 g) were divided into two groups (30 fish per tank, each treatment in triplicate) and treated with 0.0% (control) and 1.0% Ala-Gln for 56 days. The growth performance improved significantly with dietary Ala-Gln supplementation. Transcriptome profiles of dietary Ala-Gln supplementation in sturgeon were generated using second-generation Illumina sequencing technology. A total of 2891 differentially expressed genes (DEGs) were obtained, including 901, which were upregulated, and 1990, which were downregulated, in the treatment group relative to the control group. These genes are mainly involved in the general function, regulation of replication, recombination and repair, signal transduction mechanisms, amino acids and lipid transport

This study aimed to determine the effects of dietary sodium butyrate (NaB) on the growth and gut health of triploid Oncorhynchus mykiss juveniles (8.86 ± 0.36 g) fed a low fish meal diet for 8 weeks, including the inflammatory response, histomorphology, and the composition and functional prediction of microbiota. Five isonitrogenous and isoenergetic practical diets (15.00% fish meal and 21.60% soybean meal) were supplemented with 0.00% (G1), 0.10% (G2), 0.20% (G3), 0.30% (G4), and 0.40% NaB (G5), respectively. After the feeding trial, the mortality for G3 challenged with Aeromonas salmonicida for 7 days was lower than that for G1 and G5. The optimal NaB requirement for triploid O. mykiss based on weight gain rate (WGR) and the specific growth rate (SGR) was estimated to be 0.22% and 0.20%, respectively. The activities of intestinal digestive enzymes increased in fish fed a NaB diet compared to G1 (p < 0.05). G1 also showed obvious signs of inflammation, but this inflammation was significantly alleviated with dietary NaB supplementation. In comparison, G3 exhibited a more complete intestinal mucosal morphology. Dietary 0.20% NaB may play an anti-inflammatory role by inhibiting the NF-κB-P65 inflammatory signaling pathway. Additionally, the relative abundance of probiotics was altered by dietary NaB. In conclusion, dietary 0.20% NaB improved the intestinal health of triploid O. mykiss fed a low fish meal diet.