Optimum feeding frequency of juvenile largemouth bass (Micropterus salmoides) reared in in-pond raceway recirculating culture system

Interactions between feed protein source and feeding frequency on growth performance and health status of largemouth bass (Micropterus salmoides)

In order to evaluate the effects of the interaction between different proteins and feeding frequency on largemouth bass (Micropterus salmoides) and to provide scientific guidance for the application of novel proteins and the corresponding optimal feeding strategy, a two-factorial design (5 × 3) with five protein feeds (fishmeal (FM), Clostridium autoethanogenum protein (CAP), Tenebrio molitor (TM), Chlorella meal (ChM), cottonseed protein concentrate (CPC)), and three feeding frequency (1, 2, and 3 times/d; FF1, FF2, FF3) was designed in culturing largemouth bass (initial weight, 2.98 ± 0.22 g/fish) for 8 weeks. Z-score combined with cluster analysis was used to analyze and compare the effects of different treatments on different indicators, such as growth performance, feed utilization, antioxidant capacity, and immune response to draw a general picture of the relationship among all these massive biomarkers. The results showed that different protein sources and feeding frequencies had significant interactive effects on growth performance, feed utilization efficiency, body lipid, and health status of largemouth bass. Fish fed with ChM feed showed similar performance to that in FM group, implying its potential for complete replacement of fishmeal in largemouth bass. Fish fed with CAP, TM, and CPC feeds showed worse performance compared to FM and ChM groups, characterized by poor growth and feed utilization, enhanced stress, chronic inflammation, and varying symptoms of histological changes in the liver and intestine, which demonstrated the adverse effects of the complete replacement of fishmeal by these three proteins. In terms of feeding frequency, fish fed with FM feed in FF3 group led to liver hypertrophy, fat accumulation, and the risk of fatty liver, while inducing liver inflammation. In addition, the TM and CAP group had the higher expression levels of inflammatory factors at FF3 group, which displayed that the interactions between FM, CAP, TM feeds and feeding frequency at FF3 might aggravate the occurrence of liver inflammation and oxidative damage of hepatocytes. Overall, FF2 had higher feed efficiency, protein efficiency, antioxidant enzyme and lysozyme activities, lower MDA content, and lower gene expression of inflammatory cytokines and could be considered as the optimum feeding frequency for largemouth bass fed with different protein feeds.

Comparative Analysis of Nutritional Quality, Serum Biochemical Indices, and Visceral Peritoneum of Grass Carp (Ctenopharyngodon idellus) Fed with Two Distinct Aquaculture Systems

This study scrutinized the nutritional quality and serum biochemical indices of grass carp (Ctenopharyngodon idellus) cultivated in traditional pond intercropping (TPI) and in-pond raceway system (IPRS) aquaculture setups. The findings showed that the TPI group exhibited a superior water-holding capacity, while the IPRS showcased heightened crude lipid content and levels of textural properties such as springiness. Moreover, significant differences emerged in the fatty acid profiles, with the TPI group manifesting higher total polyunsaturated fatty acids (ΣPUFAs), EPA, DHA, and Σn-3, while the IPRS group exhibited elevated total saturated fatty acids (ΣSFAs). In terms of amino acids, valine and histidine levels were notably higher in the IPRS group, whereas lysine levels were reduced. Volatile compound analysis revealed significant variations, with the IPRS group containing more volatile substances with a better aroma, resulting in a better odor. The IPRS group performed better in serum biochemistry analysis. Additionally, grass carp in the IPRS group displayed an improved structure and greater coverage area of the visceral peritoneum, appearing lighter in color compared to the TPI group. TPI mainly influences nutritional elements; IPRSs primarily affect muscle texture, serum biochemistry, and overall health. This study aims to fill the gap in quality comparison research and provide an important scientific basis.

Interaction of Microbiota between Fish and the Environment of an In-Pond Raceway System in a Lake

Due to its ability to collect and remove aquaculture waste, an in-pond raceway system (IPRS) has been used to decrease the uncontrolled waste discharge in the traditional cage aquaculture method in large water bodies. However, when applied to large water bodies, its environmental performance is still lacking. This study focused on analyzing the microbial characteristics and the interaction between largemouth bass (gill and gut) microbiota and the environment (water and sediment) microbiota of an IPRS. Further, it revealed the primary relationship from the perspective of microbiota in the IPRS. The results show that (1) the alpha diversity of microbiota in the water is significantly lower than that of fish and sediment. The relationship between water microbiota and fish microbiota is limited. (2) The water microbiota inside and outside the tank showed high similarity and were not significantly affected by environmental factors. (3) The SourceTrack analysis showed that fish microbiota is one of the primary sources of sediment microbiota, and more than 15% of the sediment microbiota come from fish. Microbes such as Faecalibacterium, Escherichia-Shigella, and Bacteroides can significantly enrich the sediment. Our study revealed the characteristics and preliminary interaction of fish and environmental microbiota in the IPRS. It provided a reference for evaluating microbial health status in the application of IPRS in large water bodies’ aquaculture.

Comparison of Muscle Quality of the Yellow Catfish Cultured in In-Pond Raceway Systems and Traditional Ponds

In order to understand the difference in muscle nutritional quality between yellow catfish (Pelteobagrus fulvidraco) cultured in in-pond raceway systems (IPR) and traditional ponds (TRP), two modes were used to culture the yellow catfish with the same initial body weight [average body weight (15.69 1 ± 2.28) g] for 60 days. The growth index, muscle texture characteristics, muscle nutritional components, amino acids and fatty acids of the fish were measured after the culture experiment. The results showed that the weight gain rate, specific growth rate and survival rate of IPR were significantly higher than TRP (p < 0.05). The hardness, elasticity, chewiness and resilience of the yellow catfish cultured in IPR were significantly higher than those cultured in TRP (p < 0.05). The crude protein content in the muscle of the yellow catfish cultured in IPR was significantly higher than that cultured in TRP (p < 0.01), while the content of crude fat and water was significantly lower (p < 0.01). The total amount of amino acids, essential amino acids and flavor amino acids of IPR were significantly higher than TRP (p < 0.01). The percentages of saturated fatty acids in muscle of the yellow catfish cultured in IPR and TRP were 3.59% and 3.83%, respectively, and the percentages of unsaturated fatty acids were 96.41% and 96.17%, respectively. It was concluded that the nutritional quality of yellow catfish cultured in IPR was better than that of fish cultured in TRP.

Metabolomics approach to assess the effect of siphonal autotomy on metabolic characteristics of razor clam Solen grandis

Autotomy appendages are fundamental evolutionary adaptations to escape predation. The siphon is an important foraging organ for bivalves. Here, we report the first demonstration of autotomy of the siphon in marine bivalves (razor clam Solen grandis) and the effect of siphonal autotomy in S. grandis on foraging and metabolic characteristics. In this study, the feeding rate and digestive enzyme activities upon siphonal autotomy in razor clams were investigated. Moreover, endogenous metabolites pre/post-autotomy of the siphon were investigated using liquid chromatography tandem-mass spectrometry (LC–MS). The feeding rate and digestive enzyme activities decreased significantly after siphonal autotomy in S. grandis (P < 0.05), suggesting that autotomy of the siphon negatively affected its foraging. These results might be related to the reduction in the foraging radius. Additionally, the effect of autotomy was investigated on a total of 34 differentially abundant metabolites, and pathway analysis indicated that 32 differentially enriched metabolic pathways were worthy of attention. Further integrated key metabolic pathway analysis showed that glycine, serine and threonine metabolism; taurine and hypotaurine metabolism; biotin metabolism; vitamin B6 and thiamine metabolism were significantly relevant pathways in S. grandis pre/post-autotomy of the siphon. The downregulation of glycine, taurine, and hypotaurine is expected to indicate a shortage of intermediate compounds and energy in S. grandis. Therefore, to provide the required energy and materials for siphon regeneration in S. grandis, we anticipated that it would be necessary to supplement these as exogenous metabolites from the daily diet.

Comprehensive transcriptome analysis reveals the effect of feeding rhythm on the immunity and metabolism of Acipenser dabryanus

Acipenser dabryanus is a species endemic to Yangtze River drainage in China and is listed as a critical endangered species on the IUCN Red List. In the present study, the liver and spleen transcriptomes were analyzed by comparing the data of A. dabryanus that experienced nine different feeding rhythms (once a day diurnal, T1; two times a day diurnal, T2; three times a day diurnal, T3; four times a day, T4; five times a day, T5; six times a day, T6; once a day nocturnal, Tn1; two times a day nocturnal, Tn2; and three times a day nocturnal, Tn3). Transcriptome sequencing generated 1,901,236,482 clean reads, encompassing 570.4 Gb of sequence data. The reads were assembled into 287,372 unigenes with an average length of 803 bp and an N50 of 1004 bp. KEGG analysis showed that 1,080, 1,030, and 1216 unigenes were annotated to lipid metabolism, amino acid metabolism and carbohydrate metabolism, respectively, and 2549 unigenes were annotated to the immune system category. Differentially expressed genes (DEGs) between different feeding frequency groups or between nighttime and daytime feeding were obtained and functionally enriched. Importantly, DEGs participating in nutrition metabolism and various immunoregulation pathways and their expression profiles in A. dabryanus were discussed. Interestingly, the majority of key genes related to lipid metabolism or in immunodependent gene families, such as antimicrobial peptides, Toll-like receptors, chemokines, NOD-like receptors, B cell receptors and the major histocompatibility complex, were all significantly upregulated in animals in the T6 group compared to the characteristics of animals in the T2 group that had a normal feeding frequency. In addition, light/dark rhythm also affected the immunity of A. dabryanus, and fish fed at night possessed an improved immune response than fish fed at daytime. Our study suggested that feeding six times a day is optimal for A. dabryanus juvenile growth as it enhances the organism's nutrition metabolism and immune function.