Aquaculture Nutrition

Lipid oxidation and hypoxia can lead to oxidative damage in aquatic animals. This study explored the effects of Scoparia dulcis extracts (SDE) on lipid oxidation, fish growth performance, digestive ability, antioxidant capacity, and hypoxia tolerance ability. The results showed that SDE decreased malonaldehyde (MDA), conjugated diene (CD), and peroxide value (PO) in the linoleic acid and linolenic acid as well as in fish feed. Broken-line analysis revealed that the optimal acetone extract of S. dulcis (AE) supplements was 4.02, 4.01, and 4.01 g kg⁻¹ determined from PO, CD, and MDA, respectively. Dietary AE supplementation increased feed intake and specific growth rate and activities of amylase, trypsin, and lipase as well as alkaline phosphatase in fish hepatopancreas and gut. Polynomial regression analysis showed that optimal dietary AE supplement was 3.61 g kg⁻¹ diet determined from weight gain. Furthermore, dietary AE supplementation decreased MDA content and increased glutathione content and the activities of glutathione peroxidase, catalase, superoxide dismutase, and glutathione reductase in fish digestive organs, gills, erythrocytes, and muscle. Dietary AE supplementation increased durative time (DT) and oxygen consumption rate (OCR) under hypoxia condition. Based on polynomial regression analysis, optimal dietary AE supplements were 4.73 and 4.60 g kg⁻¹ diet determined from DT and OCR for hypoxia tolerance in fish, respectively. According to our current research, SDE’s antioxidant capacity may be attribute to their phenolic chemicals.

A feeding study lasting 30 days was carried out to determine the effects of dietary Oryzanol (Ory) on the survival, growth, antioxidant capacity, peptic enzymes, as well as lipid metabolism of Larimichthys crocea larvae (11.87 ± 0.59 mg) using four different Ory concentrations in microfeed formulations (0, 20, 40, and 80 mg/kg), all preserving isolipidic (18.25% crude lipid) and isonitrogenous (52.08% crude protein) conditions. Results revealed that larvae given 40 and 80 mg/kg Ory revealed markedly higher survival rates; in particular, the 80 mg/kg Ory larvae exhibited a considerably higher specific growth rate than the control. Furthermore, the 80 mg/kg dietary Ory resulted in increased peptic enzyme activity, indicating heightened digestive capabilities of larvae. Meanwhile, Ory supplementation at 20, 40, and 80 mg/kg also increased antioxidant enzyme activities and reduced malondialdehyde levels, indicating an enhanced antioxidant capacity. Moreover, the incorporation of 20 and 40 mg/kg Ory demonstrated efficacy in enhancing the lipid metabolism of the larvae. This was evident in the reduction of triglyceride and total cholesterol levels in the larval visceral mass, attributed to the downregulation of genes that participate in lipid synthesis, and the upregulation of genes associated with lipid catabolism. Overall, the study suggests that the addition of Ory (ranging from 40 to 80 mg/kg) significantly improves both survival and developmental aspects, possibly mediated by enhanced digestion and antioxidative effects, alongside the induction of lipid metabolism in Larimichthys crocea larvae.

Tannin (TA), as a natural phenolic compound with strong antioxidant activity, has been used as a feed additive for various animals. In this study, we fed a diet containing 800 mg/kg of tannin on Litopenaeus vannamei for 56 days and then subjected to acute ammonia stress for 48 hr to investigate the effect of dietary tannin on the ammonia stress response of L. vannamei through transcriptomic and metabolomic analysis. The transcriptome analysis indicated that ammonia stress-induced differential expression of 4,185 genes, while tannin-fed shrimp only had 964 differentially expressed genes. Compared with the TA_0 group, 59 pathways were significantly altered, and the pathways of “starch and sucrose metabolism,” “retinol metabolism,” “arachidonic acid metabolism,” “lysosome,” and “amino sugar and nucleotide sugar metabolism” were highly enriched in the TS_0 group. Compared with the TS_0 group, six pathways were significantly altered, and the pathways of “dilated cardiomyopathy,” “complement and coagulation cascades,” “cardiac muscle contraction,” “fructose and mannose metabolism,” “cGMP-PKG signaling pathway,” and “beta-alanine metabolism” were significantly enriched in the TS_800 group. Metabolomic analysis showed that a total of 107 differential metabolites (DMs) were identified in the TS_0 vs. TA_0 group, while 75 DMs were identified in the TS_800 vs. TS_0 group. Based on KEGG annotation, it was found that a large amount of DM was significantly enriched in amino acid metabolism pathways in the TS_0 group, including “arginine and proline metabolism,” “alanine, aspartic acid, and glutamic acid metabolism,” “β-Alanine metabolism and tyrosine metabolism” indicated that tannins affect the metabolism of amino acids. The integration of DEGs and DMs indicates that dietary tannins highly alter the digestion and absorption functions of proteins, as well as the biosynthesis and metabolism of amino acids. This study provides new insights into the adaptation of Pacific white shrimp to ammonia stress and the addition of tannins to feed to enhance immune function.

This study aimed to examine the effect of various live foods on the fatty acids (FAs) and amino acids (AAs) profiles in Persian sturgeon (Acipenser persicus) larvae. One thousand and two hundred larvae were cultured in circular concrete tanks, and four treatments were administered as: (1) Artemia + Daphnia, (2) Artemia, (3) Artemia + Chironomid, and (4) Chironomid. Each treatment was considered as three replicates over an 11-day period. At the end of the experiment, treatment 1 (Artemia + Daphnia) showed the highest average weight of larvae, and the lowest weight was observed in treatment 4 (Chironomid). Survival rate ranged from 83.84% to 88.86% and no significant difference was observed among the groups (). Among Artemia-fed larvae, the predominant FAs were docosahexaenoic acid (DHA), oleic acid (ω9), and monounsaturated fatty acids (MUFA), while saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) (ω3 + ω6) were present in a lesser proportion (). In larvae fed with Artemia and Daphnia, the predominant proportions were observed in SFAs, eicosapentaenoic acid (EPA), ω3, DHA + EPA, and the n3/n6 ratio, all registering the highest percentages. Conversely, MUFA, ω6, and the DHA/EPA ratio displayed the lowest percentages (). Moreover, larvae fed with Artemia exhibited higher levels of ω6, PUFA (ω3 + ω6), and DHA/EPA ratio. In contrast, larvae fed with Chironomid showed lower levels of EPA, DHA + EPA, and n3/n6 ratio (). Among larvae fed with Chironomid, solely the DHA/EPA ratio exhibited a higher value compared to larvae fed with Artemia and Daphnia (). The amount of leucine in fish fed Artemia + Daphnia was more than the other treatments (). This study revealed a significant difference in amino acids composition among various live foods (), but no significant difference in AAs was observed in the body of Persian sturgeon larvae (). The results of this study suggest that the Persian sturgeon larvae possess the ability to maintain a balanced state of AAs. It is also evident that the FA profile of different live foods can affect the overall FA levels in the body of Persian sturgeon larvae, ultimately contributing to the enhancement of fish survival rate and growth.

Fishmeal is an important protein source in aquafeed. However, due to the limited natural resources, fishmeal is in short supply, resulting in a price surge for fishmeal. Here, we reported a kind of Chinese medicine residue, endothelium corneum gigeriae galli residue (ECGGR), as a fishmeal substitute in the diets of Trachinotus ovatus. Six isonitrogenous and isolipidic diets were formulated, substituting fishmeal at 0%, 6.25%, 12.5%, 18.75%, 25%, and 31.25%. There was no significant difference in the growth performance when the fishmeal substitution level was no more than 25%. The smallest FCR was obtained at the 18.75% substitution level. Furthermore, substituting ECGGR for fishmeal had no effect on whole-body and muscle proximate compositions, except when the replacement level exceeded 25%, which led to a decrease in whole-body moisture and an increase in whole-body crude protein. The contents of Gly, Cys, Ile, Tyr, Pro, and EAAs/TAAs were altered as the substitution level varied. However, dietary replacement of fishmeal with ECGGR did not degrade muscle protein quality, according to a nutritional evaluation of muscle essential amino acid composition. In terms of hepatic antioxidant capacity, neither the overall antioxidant status nor the expression of genes in the Nrf2-ARE pathway was altered by dietary ECGGR. Moreover, the expressions of p65, TNF-α, and IL-8 in the intestine were upregulated at the 31.25% substitution level. Also, more goblet cells were observed in the intestine at substitution levels of 25% and 31.25%. In conclusion, ECGGR can substitute for fishmeal at the optimal level of 18.75% without adversely affecting the growth performance, protein quality, or hepatic and intestinal health of golden pompano.

The spotted seatrout (Cynoscion nebulosus)—an important commercial species—has a high potential for aquaculture in the Gulf of Mexico. To optimize its feeding during larval rearing, this study aims to evaluate the primary gastric (pepsin), intestinal (leucine aminopeptidase and alkaline phosphatase), and pancreatic (alkaline protease, trypsin, chymotrypsin, amylase, and lipase) enzyme activities from hatching to day 30. A multivariate analysis identified three digestive enzyme development stages during the spotted seatrout larval transformation. The first stage occurred between 1 (mean ± standard error (SE) = 1.73 ± 0.14 millimeter (mm) standard length (SL)) and 3 (2.14 ± 0.07 mm SL) days after hatching (DAH); a period of digestive stability showed the highest activity in amylase and bile salt-dependent lipase. The second stage (from 4 (2.53 ± 0.09 mm SL) to 20 (10.92 ± 0.51 mm SL) DAH) was a period of digestive transition, during which leucine aminopeptidase, chymotrypsin, and alkaline proteases were identified as the predominant enzymes from 4 to 5 DAH. In the third stage—a period of digestive stability—pepsin was the major enzyme that occurred between 25 (16.51 ± 0.81 mm SL) and 30 (25.91 ± 0.82 mm SL) DAH. These results indicate that the spotted seatrout larvae have a digestive system adapted to lipids and carbohydrates at the onset of feeding, with an immediate transition to protein digestion when exogenous feeding begins. Additionally, the digestive system of the spotted seatrout may be considered mature at 25 DAH. Further research is needed to elucidate the mechanisms of digestive tract development in the spotted seatrout larvae.