Dual-Function Analysis of Astaxanthin on Golden Pompano (Trachinotus ovatus) and Its Role in the Regulation of Gastrointestinal Immunity and Retinal Mitochondrial Dysfunction Under Hypoxia Conditions

Effect of Hypoxia on the Gut Microflora of a Facultative Air-Breathing Loach Lepidocephalichthys guntea

One of the main risks to fish health in an aquatic environment is hypoxia, which can either lead to respiratory failure or the emergence of various diseases in a fish population. This investigation examined the impact of hypoxia on the gut bacteria of a loach, Lepidocephalichthys guntea, which under the dissolve oxygen stress can gulp air from surface and breathe using its posterior intestine. High-throughput sequencing was used to examine the anterior and posterior parts of the gut of L. guntea during both normoxia and hypoxia. According to the community profiling of the gut bacteria, prolonged exposure to hypoxia increased the diversity and abundance of bacteria in the posterior part while decreasing both in the anterior part of the gut. Additionally, for both parts of the gut, the core microbiota showed a significant alteration during hypoxia. In correlation network analysis, a more interactive and intricate network was developed at normoxia. According to the comparative analyses of the gut bacteria, hypoxia causes more pronounced alterations in the posterior gut than the anterior gut at various taxonomic levels. As a consequence of hypoxia, several genera like Aeromonas, Pseudomonas, Plesiomonas, Acinetobacter, and Enterobacter were replaced by Streptococcus, Escherichia-Shigella, Janthinobacterium, and Clostridia. A surge in probiotic genera, including Bifidobacterium, Lactobacillus, Blautia, and Cetobacterium, was also seen. The fatty acid biosynthesis pathway was induced only in hypoxia, although all other metabolic pathways were present in both situations, albeit with fewer hits in hypoxia.

Effects of dietary astaxanthin supplementation on growth performance, antioxidant status, immune response, and intestinal health of rainbow trout (Oncorhynchus mykiss)

A feeding trial was conducted to assess the impacts of dietary astaxanthin from wall-broken Haematococcus pluvialis (WBHPA) on the growth performance, antioxidant status, immune response, and intestinal health of rainbow trout (Oncorhynchus mykiss). Six experimental diets were formulated with various concentrations of WBHPA, ranging from 0 to 8.4 g/kg (containing 0 to 125 mg/kg astaxanthin). Each diet was fed to triplicate groups of rainbow trout (mean initial weight of 561 g) twice daily for 9 consecutive weeks. The survival rate and feed intake of fish exhibited no significant differences among the dietary groups (P > 0.05). Similarly, dietary inclusion of 25 to 100 mg/kg astaxanthin did not significantly affect the weight gain and daily growth coefficient (P > 0.05), but excessive inclusion of astaxanthin (125 mg/kg) slightly depressed these parameters (P < 0.05). Dietary inclusion of 25 to 50 mg/kg astaxanthin increased the activities of intestinal digestion and absorption enzymes (lipase, creatine kinase, and alkaline phosphatase), while the inclusion of 25 to 75 mg/kg astaxanthin improved the immune response of fish. Furthermore, regardless of inclusion level (25 to 125 mg/kg), dietary astaxanthin supplementation strengthened the intestinal mucosal barrier function and improved antioxidant activity, thereby promoting intestinal development. Conclusively, 25 to 75 mg/kg astaxanthin from WBHPA was recommended to be included in diets for rainbow trout.

Different reoxygenation rates induce different metabolic, apoptotic and immune responses in Golden Pompano (Trachinotus blochii) after hypoxic stress

Dissolved oxygen (DO) is essential for teleosts, and fluctuating environmental factors can result in hypoxic stress in the golden pompano (Trachinotus blochii). However, it is unknown whether different recovery speeds of DO concentration after hypoxia induce stress in T. blochii. In this study, T. blochii was subjected to hypoxic conditions (1.9 ± 0.2 mg/L) for 12 h followed by 12 h of reoxygenation at two different speeds (30 mg/L per hour and 1.7 mg/L per hour increasing). The gradual reoxygenation group (GRG), experienced DO recovery (1.9 ± 0.2 to 6.8 ± 0.2 mg/L) within 3 h, and the rapid reoxygenation group (RRG), experienced DO recovery (1.9 ± 0.2 to 6.8 ± 0.2 mg/L) within 10 min. Physiological and biochemical parameters of metabolism (glucose, glycegon, lactic acid (LD), lactate dehydrogenase (LDH), pyruvic acid (PA), phosphofructokinase (PFKA), and hexokinase (HK), triglyceride (TG), lipoprotein lipase (LPL), carnitine palmitoyltransferase 1 (CPT-1)) and transcriptome sequencing (RNA-seq of liver) were monitored to identify the effects of the two reoxygenation speeds. Increased LD content and increased activity of LDH, PA, PFKA, and HK suggested enhanced anaerobic glycolysis under hypoxic stress. LD and LDH levels remained significantly elevated during reoxygenation, indicating that the effects of hypoxia were not immediately alleviated during reoxygenation. The expressions of PGM2, PFKA, GAPDH, and PK were increased in the RRG, which suggests that glycolysis was enhanced. The same pattern was not observed in the GRG. Additionally, In the RRG, reoxygenation may promote glycolysis to guarantee energy supply. However, the GRG may through the lipid metabolism such as steroid biosynthesis at the later stage of reoxygenation. In the aspect of apoptosis, differentially expressed genes (DEGs) in the RRG were enriched in the p53 signaling pathway, which promoted cell apoptosis, while DEGs in the GRG seem to activate cell apoptosis at early stage of reoxygenation but was restrained latterly. DEGs in both the RRG and the GRG were enriched in the NF-kappa B and JAK-STAT signaling pathways, the RRG may induce cell survival by regulating the expression of IL-12B, COX2, and Bcl-XL, while in the GRG it may induce by regulating the expression of IL-8. Moreover, DEGs in the RRG were also enriched in the Toll-like receptor signaling pathway. This research revealed that at different velocity of reoxygenation after hypoxic stress, T. blochii would represent different metabolic, apoptotic and immune strategies, and this conclusion would provide new insight into the response to hypoxia and reoxygenation in teleosts.

Effects of anti-stress agents on the growth performance and immune function in broiler chickens with vaccination-induced stress

The aim of this study was to evaluate the effects of anti-stress agents on the growth performance and immune function of broilers under immune stress conditions induced by vaccination. A total of 128, 1-day-old Arbor Acres broilers were randomly divided into four groups. Group normal control (NC) was the control group. Group vaccination control (VC), T 0.5%, and T 1% were the treatment groups, which were nasally vaccinated with two doses of the Newcastle disease virus (NDV) vaccine. The chicks in groups T 0.5% and T 1% were fed conventional diets containing 0.5% and 1% anti-stress agents. Thereafter, these broilers were slaughtered on 1, 7, 14, and 21 days post-vaccination. The results indicated that anti-stress agents could significantly reduce serum adrenocorticotropic hormone (ACTH) (P < 0.01) and cortisol (CORT) (P < 0.05) levels, and improve the growth performance (P < 0.05) and immune function of broilers (P < 0.05); However, the levels of malondialdehyde (MDA) (P < 0.05) were decreased, and the decreased total antioxidant capacity (T-AOC) (P < 0.01) levels mediated by vaccination were markedly improved. In addition, anti-stress agents could attenuate apoptosis in spleen lymphocytes (P < 0.01) by upregulating the ratio of Bcl-2 to BAX (P < 0.01) and downregulating the expression of caspase-3 and -9 (P < 0.01), which might be attributed to the inhibition of the enzymatic activities of caspase-3 and -9 (P < 0.05). In conclusion, anti-stress agents may improve growth performance and immune function in broilers under immune-stress conditions.RESEARCH HIGHLIGHTS Investigation of effects and mechanism of immune stress induced by vaccination.Beneficial effect of anti-stress agents on growth performance, immune function, oxidative stress, and regulation of lymphocyte apoptosis.Demonstration of the effects of apoptosis on immune function in the organism.

Growth promoter, immune response, and histopathological change of prebiotic, probiotic and synbiotic bacteria on Nile tilapia

This study aimed at determining the influence of prebiotic, probiotic, and synbiotic supplemented diets on Oreochromis niloticus. Fish with initial body weight (25.8 ± 1.2) g and length range from (13.5 ± 1.5) cm were collected and randomized to four dietary treatments for 60 days. Furthermore, fish were divided into three groups in triplicate; A0 control (-ve), A1 control (+ve) infected with V.anguillarium, and a third non-treated group. Moreover, the third group further separated into two groups, A and B. Group (A) was treated with prebiotic, probiotic, and symbiotic (A2, A3, and A4), while group (B) was infected with V.anguillarium then treated with prebiotic, probiotic and symbiotic (A5, A6, and A7). The results revealed that all treatments supplemented with synbiotics represented highly significant increase (p ≤ 0.05) in (SGR), BWG percentage, relative growth rate (%), lysozyme activity, IMG, SOD, and CAT. At the same time, they exhibited a significant decrease in MAD and FCR. Besides, fish that feed dietary supplementation with prebiotics, probiotics, and synbiotics revealed a significant increase in RBCs, WBCs, and Hb. In contrast, they showed a significant decrease in ALT, AST, albumin, total protein, globulin, creatinine, and urea compared with control. Additionally, high survival rates were recorded in groups that received a diet supplemented with probiotics, followed by prebiotics and synbiotics.