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This study investigated the effects of dietary sodium butyrate (NaB) on growth, serum biochemical indices, intestine histology, and gut microbiota of largemouth bass (Micropterus salmoides). A basal diet was formulated and used as the control diet (Con), and five additional diets were prepared by supplementing NaB (50%) in the basal diet at 2.0, 4.0, 8.0, 12.0, and 16.0 g/kg inclusion (NaB-2, NaB-4, NaB-8, NaB-12, and NaB-16 diets). Then, the six diets were fed to triplicate groups of largemouth bass juveniles (2.4 ± 0.1 g) for 8 weeks. NaB supplementation linearly and quadratically affected weight gain (WG) and feed intake (FI) (P < 0.05). The NaB-16 group displayed lower WG (− 6.8%) and FI than the Con group (P < 0.05), while no differences were found in WG and feed conversion ratio between the other NaB groups and Con group (P > 0.05). Serum alkaline phosphatase and lysozyme activities were higher in the NaB groups (P < 0.05), and D-lactate content was lower in the NaB-12 group (P < 0.05) than the control. Intestinal lipase activity in NaB-2, NaB-4 group, and villi width in NaB-8 group were also higher than those in the Con group (P < 0.05). Compared to the Con group, the intestinal abundances of Firmicutes and Mycoplasma were increased and the abundances of Proteobacteria, Achromobacter and Plesiomonas were decreased in NaB-4 and NaB-16 groups (P < 0.05). In conclusion, dietary NaB did not promote the growth of juvenile largemouth bass, but positively modulated the intestinal microbial community. [ABSTRACT FROM AUTHOR]

Grass carp is one of the most important freshwater aquaculture fish in China. Though a few molecular markers had been reported, it was not enough for grass carp germplasm improvement and protection. In order to verify the effectiveness and practicability of insert/deletion mutations reported in grass carp genome, 85 insert/deletion mutations were randomly selected and analyzed. After simple sequence analysis and attempting primer design, 49 markers were removed due to being simple sequence repeats or unable to design primer for them. Finally, 36 insert/deletion mutations were successfully characterized by STR genotyping method in 32 wild grass carp (collected from Pearl River). The mean effective number of alleles (Ne), observed heterozygosity (Ho), expected heterozygosity (He) and polymorphic information content (PIC) were 1.4976, 0.3190, 0.2970 and 0.2349, respectively. Among all the 36 insert/deletion mutations, three deviated significantly from Hardy–Weinberg equilibrium (P < 0.05). In addition, three pairs of loci (ID-13F with ID-24H, ID-20F with ID-21H and ID-39F with ID-64H) had significant linkage disequilibrium (P < 0.05). Those insert/deletion mutations may lay the foundation for germplasm improvement and protection in grass carp. [ABSTRACT FROM AUTHOR]

To compare the flesh quality of large yellow croaker cultured with three different modes, enclosure culture (EC), cage culture with feeding trash fish (CCF) and cage culture with feeding formula diet (CCD), thirty six fish individuals of EC (484.6 ± 79.8 g), CCF (432.7 ± 87.9 g) and CCD (416.9 ± 49.5 g) were sampled to measure body color, flesh water holding capacity, flesh proximate composition, amino acids and fatty acids composition, and collagen and inosinic acid contents. The analysis showed that there was no significant difference in the yellowness of skin and the contents of crude protein and inosinic acid between CCD and EC (P >0.05), and the two modes showed higher values than CCF ( P < 0.05). Most of the amino acids (AA) in flesh were higher in EC than in CCF ( P < 0.05), but CCD showed no difference in AA composition from the other two modes ( P > 0.05). EC and CCD had higher contents of collagen, free AA and lower drip loss than CC ( P < 0.05). In polyunsaturated fatty acids, EC showed significantly higher levels of C20:5n-3 and C22:6n-3 than CCF and CCD ( P < 0.05), but CCD had significantly higher C18:2n-6 than CCF and EC ( P < 0.05). In conclusion, the flesh quality of CCD fish is similar to EC fish, and these two modes have better flesh quality than CCF. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the effects of partially replacing dietary fish meal (FM) with soy protein concentrate (SPC) on growth, body composition, digestive enzyme activities, and nutrient digestibility of white shrimp. Five isonitrogenous diets with SPC inclusion levels of 0.0, 2.5, 5.0, 7.5 and 10.0%, were prepared to replace 0.0, 12.5, 25.0, 37.5, and 50.0% FM in basal diet containing 20.0% FM, respectively, and fed to white shrimp with an initial body weight of 1.80 g. After 49 days feeding, 5.0% SPC diet did not affect the growth of white shrimp ( P > 0.05), but weight gain was decreased ( P < 0.05) and the apparent digestibility of dry matter and protein and hepatopancreas protease activity were decreased ( P < 0.05) by the inclusion of 7.5% or 10.0% SPC. With the increase of dietary SPC level, the whole-body crude protein content, serum triglycerides, and cholesterol contents decreased ( P < 0.05), while the whole-body lipid content increased ( P < 0.05). Muscle amino acids showed no significant differences ( P > 0.05) among treatments except glycine (Gly). The above results indicated that 25% FM could be substituted by SPC, and the SPC inclusion level was 5% without negative effects on the growth of white shrimp. [ABSTRACT FROM AUTHOR]

Extruded and pelleted feeds were fed with different amounts (100, 90, 80, and 70% of satiation) to channel catfish (42 g initial weight) and the effects on growth, nutrient retention, and serum biochemistry were examined. The two feeds were designed with the same formula (containing 308 g kg crude protein and 53 g kg crude lipid), and were fed to eight treatments of fish (pelleted feed with a satiation of 100, 90, 80, 70% and extruded feed with a satiation of 100, 90, 80, 70%) with triplicate cage per treatment (20 fish per cage) for 10 weeks. The results indicated that weight gain (WG) of the eight groups were 371.1, 328.1, 302.1, 281.1 and 370.5, 334.0, 311.0, 285.3%, respectively. The fish fed extruded and pelleted feed at the same feeding rate showed no significant differences in growth performance, whole-body composition, and nutrient retention ( P > 0.05). In both extruded and pelleted feeds, WG, feed conversion ratio (FCR), intraperitoneal fat ratio (IFR), whole-body lipid content, lipid retention (LR), and serum triglyceride (TG) content decreased ( P < 0.05), but protein retention (PR) increased from 35.3 to 39.4% in pelleted feeds and from 35.9 to 39.7% in extruded feeds with the decrease of feeding rate from satiation (100%) to 70% of satiation ( P < 0.05). The above results demonstrated that channel catfish fed extruded feed had the similar growth to that fed pelleted feed with the same formula. The utilization of protein and feed could be improved by the reduced feeding rate from satiation (100%) to 70% of satiation. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the effects of extruded diets and pelleted diets with varying protein levels on growth performance and nutrient utilization of tilapia. Six diets, containing three levels of crude protein (CP) of 250, 280 and 310 g kg, were prepared by pelleting (sinking) or extruding (floating) and were fed to tilapia juveniles (body weight of 8.0 ± 0.1 g). After 8-week feeding, the weight gain (WG) and feed conversion ratio (FCR) of the six groups (pelleted diets with protein of 250, 280, 310 g kg and extruded diets with protein of 250, 280, 310 g kg) were 561.8, 609.4, 686.5, 593.6, 663.7, 683.0 and 1.49, 1.38, 1.22, 1.42, 1.25, 1.23 %, respectively. The WG, protein retention (PRE), lipid retention and energy retention (ERE) of fish fed pelleted diets increased, while FCR decreased as dietary protein increased. In extruded diets, the fish fed 280 g kg CP had a higher WG, PRE, ERE and a lower FCR than fish fed 250 g kg CP and had the similar growth as the fish fed 310 g kg CP. The fish fed 280 g kg CP had the highest apparent digestibility coefficient of dry matter and CP in both pelleted diets and extruded diets. The fish fed extruded diets had better growth and better nutrient utilization than fish fed pelleted diets when dietary protein level was 250 or 280 g kg, but when dietary protein level was 310 g kg, the fish fed extruded diet showed similar growth as the fish fed pelleted diet. In both extruded and pelleted diets, the tilapia fed 280 or 310 g kg CP had lower activity of aspartate aminotransferase than fish fed 250 g kg CP, and the high-density lipoprotein cholesterol levels of groups of 250 and 280 g kg CP were lower than that of 310 g kg CP group. The above results demonstrate that tilapia fed an extruded diet have a better growth than the fish fed a pelleted diet at a low dietary CP level but not at a high dietary CP level. The dietary protein requirement of tilapia could be 310 g kg for a pelleted diet or 280 g kg for an extruded diet. [ABSTRACT FROM AUTHOR]

A 45-day feeding trial was conducted to evaluate the effects of dietary citric acid on growth, digestive enzyme and disease resistance of white shrimp, Litopenaeus vannamei. Shrimp with initial body weight of 5.57 ± 0.21 g were fed with basal diet supplemented with 0.0 g kg (control), 1.0, 2.0, 3.0, 4.0 and 5.0 g kg citric acid. Results showed that weight gain was increased by 15.9 % and feed conversion ratio was decreased by 0.17 by 2.0 g kg dietary citric acid compared with control group ( P < 0.05). Intestinal protease activity of shrimp fed 2.0 g kg citric acid was significantly higher ( P < 0.05) than that of control group. No significant difference was found in intestinal amylase activity among treatments ( P > 0.05). The activities of serum phenoloxidase, superoxide dismutase and lysozyme in 2.0 and 3.0 g kg citric acid group were significantly higher, and accumulative mortalities of the two groups on the fourth day after injection of Vibrio alginolyticus were significantly lower than those of control group ( P < 0.05). Results above demonstrated that dietary citric acid could improve growth performance, immunity and resistance against V. alginolyticus. The supplementation level of citric acid in diet was suggested to be 2.0-3.0 g kg for white shrimp. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the effects of three commercial astaxanthin preparations (100 mg kg diet) with different solubilities in water, from DSM (Dutch State Mines), BASF (Badische Anilin and Soda Fabrik) and Wisdom Company on pigmentation of flesh and antioxidation of flesh, serum and liver in rainbow trout with an initial weight of 52.07 g. After 60 days of feeding, there were no significant differences in growth or flesh proximate composition of rainbow trout among groups ( P > 0.05); the Salmo Fan score, redness and astaxanthin content of flesh in rainbow trout fed diets supplemented with astaxanthins were higher than those of the control group ( P < 0.05). At 0, 12, 24, 48 and 72 h after thawing, the flesh malondialdehyde (MDA) content of the three astaxanthin groups was lower than that of the control group ( P < 0.05). The total antioxidation capacity (T-AOC) of liver in the three astaxanthin groups was significantly higher, but serum catalase (CAT) activities were lower, than that of the control group ( P < 0.05). The results indicate that addition of 100 mg kg astaxanthin from DSM, BASF or Wisdom to the diet could improve flesh redness and liver T-AOC, reduce serum CAT, SOD and flesh MDA and extend the shelf life of flesh, in spite of the different solubilities of the three sources in water. [ABSTRACT FROM AUTHOR]

Growth differentiation factor 9 ( GDF9) is a member of the transforming growth factor β (TGF-β) superfamily with a key role in regulating follicle development. In this study, the GDF9 full-length genomic DNA and cDNA were isolated and characterized from the gibel carp ovary using rapid-amplification of cDNA ends (RACE) and LD-PCR. The full-length genomic DNA and cDNA sequences of GDF9 are 3979 and 2044 bp which code 428 amino acid residues with a specific RKKR protease cleavage site of TGF-β superfamily. Sequence analysis showed that gibel carp was similar to zebrafish and other fish species. Spatio-temporal expression analysis using real-time quantitative PCR revealed that GDF9 mRNA was largely expressed in ovary and testis. GDF9 is mainly present at stage I follicles indicating its important role in early follicles development. The same result was obtained in immunohistochemistry localization of GDF9 protein. Within the follicle, the follicle layer cells were barely expressed whereas GDF9 mRNA was mostly expressed in the oocytes. Supplemented with human chorionic gonadotropin (hCG) in isolated follicles, the expression of GDF9 mRNA was increased firstly and then decreased. The results of this study indicated that GDF9 gene played a role in fish during development of follicles, especially in the early stage follicles. [ABSTRACT FROM AUTHOR]