Effect of bovine lactoferricin on the growth performance, digestive capacity, immune responses and disease resistance in Pacific white shrimp, Penaeus vannamei

Protective effects of butyric acid during heat stress on the survival, immune response, histopathology, and gene expression in the hepatopancreas of juvenile pacific shrimp (L. Vannamei)

This study looked at the effects of adding butyric acid (BA) to the diets of juvenile Pacific shrimp and how it affected their response to survival, immunity, histopathological, and gene expression profiles under heat stress. The shrimp were divided into groups: a control group with no BA supplementation and groups with BA inclusion levels of 0.5 %, 1 %, 1.5 %, 2 %, and 2.5 %. Following the 8-week feeding trial period, the shrimp endured a heat stress test lasting 1 h at a temperature of 38 °C. The results showed that the control group had a lower survival rate than those given BA. Interestingly, no mortality was observed in the group receiving 1.5 % BA supplementation. Heat stress had a negative impact on the activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in the control group. Still, these activities were increased in shrimp fed the BA diet. Similar variations were observed in AST and ALT fluctuations among the different groups. The levels of triglycerides (TG) and cholesterol (CHO) increased with high temperatures but were reduced in shrimp-supplemented BA. The activity of an antioxidant enzyme superoxide dismutase (SOD) increased with higher BA levels (P < 0.05). Moreover, the groups supplemented with 1.5 % BA exhibited a significant reduction in malondialdehyde (MDA) content (P < 0.05), suggesting the potential antioxidant properties of BA. The histology of the shrimp's hepatopancreas showed improvements in the groups given BA. Conversely, the BA significantly down-regulated the HSPs and up-regulated MnSOD transcript level in response to heat stress. The measured parameters determine the essential dietary requirement of BA for shrimp. Based on the results, the optimal level of BA for survival, antioxidant function, and immunity for shrimp under heat stress is 1.5 %.

Responses of growth performance, immunity, disease resistance of shrimp and microbiota in Penaeus vannamei culture system to Bacillus subtilis BSXE-1601 administration: Dietary supplementation versus water addition

This study evaluated the effects of Bacillus subtilis BSXE-1601, applied either as dietary supplementation or water addition, on growth performance, immune responses, disease resistance of Penaeus vannamei, and microbiota in shrimp gut and rearing water. During the 42-day feeding experiment, shrimp were fed with basal diet (CO and BW group), basal diet supplemented with live strain BSXE-1601 at the dose of 1 × 109 CFU kg-1 feed (BD group) and 15 mg kg-1 florfenicol (FL group), and basal diet with strain BSXE-1601 added to water at the concentration of 1 × 107 CFU L-1 every five days (BW group). Results showed that dietary supplementation of strain BSXE-1601 significantly promoted growth performance of shrimp, both in the diet and water, enhanced disease resistance against Vibrio parahaemolyticus (P < 0.05). The BD and BW groups exhibited significant increases in acid phosphatase, alkaline phosphatase, lysozyme, peroxidase, superoxide dismutase activities, phenonoloxidase content in the serum of shrimp compared to the control (P < 0.05). Meanwhile, the expression of immune-related genes proPO, LZM, SOD, LGBP, HSP70, Imd, Toll, Relish, TOR, 4E-BP, eIF4E1α, eIF4E2 were significantly up-regulated compared to the control (P < 0.05). When added in rearing water, strain BSXE-1601 induced greater immune responses in shrimp than the dietary supplement (P < 0.05). Chao1 and Shannon indices of microbiota in rearing water were significantly lower in BD group than in the control. The microbiota in rearing water were significantly altered in BD, BW and FL groups compared to the control, while no significant impacts were observed on the microbiota of shrimp gut. When supplemented into the feed, strain BSXE-1601 obviously reduced the number of nodes, edges, modules in the ecological network of rearing water. The results suggested that dietary supplementation of BSXE-1601 could be more suitable than water addition in the practice of shrimp rearing when growth performance, non-specific immunity, disease resistance against V. parahaemolyticus in shrimp were collectively considered.

Feeding rhythm of the zoea larvae of Scylla paramamosain: The dynamic feeding rhythm is not completely synchronized with photoperiod

The feeding rhythm is one of the key factors determining the success of artificial breeding of S. paramamosain. To understand the feeding rhythm of the different zoea larva developmental stages of S. paramamosain, the feeding rate, digestive enzyme activity, and expression of metabolism-related genes were investigated in the present study. The results showed that the S. paramamosain feeding rate has strong diurnal feeding rhythm, being significantly higher at 10:00-14:00 from stages ZI to ZIV. While the feeding rate peaked at 14:00 on Days 10 and 11, the peak shifted to 18:00 on Day 12. The activity of digestive enzymes amylase, pepsin and lipase decreased at night but increased in the daytime, showing a single-phase rhythm similar to that of the feeding rate, suggesting that the digestive enzyme activity was closely associated with the feeding rate during the larval development. Compared to pepsin and lipase, the activity of amylase was the most consistent with feeding rate. In particular, amylase activity peaked at 18:00 on Day 12. Due to its synchronicity with feeding activity, the activity of amylase could provide a potential reference for determining the best feeding time during zoea stages in S. paramamosain breeding. Moreover, the relative mRNA expression of metabolism-related genes SpCHH and SpFAS at most tested points was lower from 10:00 to 14:00, but higher at 18:00 to 6:00 of the next day. On the other hand, the expression patterns of SpHSL and SpTryp were converse to those of SpCHH and SpFAS. Our findings revealed that the S. paramamosain zoea has an obvious feeding rhythm, and the most suitable feeding time was 10:00-18:00 depending on different stages. The feeding rhythm is a critical aspect in aquaculture, influencing a series of physiological functions in aquatic animals. This study provides insights into the feeding rhythm during the zoea development of S. paramamosain, making a significant contribution to optimizing feeding strategy, improving aquafeed utilization, and reducing the impact of residual feed on water environment.

Effects of Brown Fishmeal on Growth Performance, Digestibility, and Lipid Metabolism of the Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

The aim of this study was to evaluate the effect of brown fishmeal in replacement of white fishmeal in the diet of Chinese soft-shelled turtles and to find the optimal amount of brown fishmeal to add. Five experimental groups were set up and fed to animals, and they were composed by different proportions of white and brown fishmeal: G1 (30% white and 25% brown fishmeal), G2 (25% white and 30% brown fishmeal), G3 (20% white and 35% brown fishmeal), G4 (15% white and 40% brown fishmeal), G5 (10% white and 45% brown fishmeal). G1 is regarded as the control group. Turtles were randomly divided into five experimental groups with four replicates each. The experiment lasted 72 days. The results showed that the WGR, SGR, FCR, and HSI of the G3 group were not significantly different from those of the control group (P > 0.05). In addition, brown fishmeal can increase the crude protein content in the muscles of them. Among the serum biochemical indices, there was no significant difference between the G3 group and the G1 group, except for the level of TG (P > 0.05). Meanwhile, the activities of AST, ALT, and CAT in the liver of the G3 group did not differ significantly from those of the G1 group (P > 0.05). However, the activities of ACP, AKP, and T-AOC were significantly decreased in the G3 group (P < 0.05). In addition, the alteration of fishmeal did not affect the digestive enzyme activities in the stomach, liver, and intestine, and there is no significant difference (P > 0.05). Importantly, with increasing brown fishmeal addition, the expression of Fas, Pparγ, Scd, and Stat3 showed a significant increase, while the expression of Bmp4 decreased significantly (P < 0.05). In this study, the addition of 20% white fishmeal and 35% brown fishmeal to the diet of Chinese soft-shelled turtles did not adversely affect growth performance. Therefore, 20% white fishmeal and 35% brown fishmeal are the most practical feed formulations for Chinese soft-shelled turtles in this study.

Bovine Lactoferrin and Hen Ovotransferrin Affect Virulence Factors of Acute Hepatopancreatic Necrosis Disease (AHPND)-Inducing Vibrio parahaemolyticus Strains

Acute Hepatopancreatic Necrosis Disease (AHPND), a highly destructive shrimp disease, has inflicted severe setbacks on the shrimp farming industry worldwide. As the use of antibiotics is discouraged due to emerging antibiotic-resistant bacteria and the pollution of ecosystems, there is a pressing demand for novel, sustainable alternatives. Hence, the influence of bovine lactoferrin (bLF) and hen ovotransferrin (OT), two natural antimicrobial proteins, on the growth of three AHPND-causing Vibrio parahaemolyticus (Vp) strains (M0904, TW01 and PV1) was examined. Additionally, we explored their potential to affect selected Vp virulence factors such as biofilm formation, swimming and swarming, cell surface hydrophobicity, and activity of released lipases and caseinases. Lag phases of all bacterial growth curves were significantly prolonged in the presence of bLF or OT (1, 5 and 10 mg/mL), and bLF (5 and 10 mg/mL) completely inhibited growth of all strains. In addition, bLF or OT significantly reduced biofilm formation (all tested bLF and OT concentrations for Vp M0904 and Vp PV1), bacterial swimming motility (0.5 mg/mL bLF and OT for Vp M0904 and Vp TW01; 1 mg/mL bLF and OT for all strains), cell surface hydrophobicity (for all strains, all bLF and OT concentrations tested except for 0.125 mg/mL OT for Vp PV1) and lipase activity (1 mg/mL bLF and OT for all strains and 0.5 mg/mL bLF and OT for Vp PV1). These promising in vitro results suggest that bLF and/or OT might be used as novel agents for combating AHPND and warrant further research to elucidate the underlying mechanisms of action to fully unlock their potential for AHPND disease management.

Histological, Physiological and Transcriptomic Analysis Reveal the Acute Alkalinity Stress of the Gill and Hepatopancreas of Litopenaeus vannamei

The pacific white shrimp (Litopenaeus vannamei) has gradually become a promising economic species in the development of saline-alkali water fishery. The study related to the stress reaction of pacific white shrimp under alkalinity stress is still limited, which is also a critical limiting factor for its saline-alkaline aquaculture. In this study, we aim to analyse the stress reaction of pacific white shrimp under acute alkalinity stress between control group (alkalinity:40 mg/L) and treatment group (alkalinity:350 mg/L) through histological observation, physiological determination and transcriptome. In the present study, during the process of acute alkalinity stress, the activities of Na+-K+-ATPase, carbonic anhydrase, sodium/hydrogen exchanger in gill related to homeostasis were significantly changed, the activities of superoxide dismutase and catalase related to antioxidant were decreased in both gill and hepatopancreas, and the activities of protease, lipase and amylase in hepatopancreas were decreased. At the same time, different degrees of histological damages were occured in the gill and hepatopancreas under acute alkalinity stress. There were 194 and 236 different expressed genes identified in gill and hepatopancreas respectively. Functional enrichment assessment indicated that the alkalinity stress-related genes in both gill and hepatopancreas were primarily involved in fatty acid metabolism, glycolysis/gluconeogenesis, glycerophospholipid metabolism. The results indicated that the functions of homeostasis regulation, antioxidation and digestion of pacific white shrimp were decreased under acute alkalinity stress, at the same time, the energy metabolism in gill and hepatopancreas were modified to cope with alkalinity stress. This work provides important clues for understanding the response mechanism of pacific white shrimp under acute alkalinity stress.

Bovine lactoferricin on non-specific immunity of giant freshwater prawns, Macrobrachium rosenbergii

This study aimed to investigate the effects of dietary Bovine lactoferricin (LFcinB) on the growth performance and non-specific immunity in Macrobrachium rosenbergii. Five experimental diets were 1.0‰ Bovine lactoferricin (LCB1); 1.5‰ Bovine lactoferricin (LCB1.5); 2.0‰ Bovine lactoferricin (LCB2); 2.5‰ Bovine lactoferricin (LCB2.5); the control group, basal diet without Bovine lactoferricin. A total of 600 prawns were randomly assigned to 5 groups in triplicate in 15 tanks for an 8-week feeding trial. The results showed the final weight, weight gain rate, specific growth rate and survival rate of prawns in the treatment groups were significantly improved versus the control (P < 0.05). The feed conversion ratio was reduced significantly in treatment groups compared to the control (P < 0.05). Compared with the control, alkaline phosphatase (AKP), acid phosphatase (ACP), lysozyme (LZM), catalase (CAT), superoxide dismutase (SOD) activities in the hepatopancreas of the treatment groups were significantly enhanced, and malondialdehyde (MDA) content was reduced significantly (P < 0.05). Compared with the control, the relative expression levels of AKP, ACP, LZM, CAT, SOD, Hsp70, peroxiredoxin-5, Toll, dorsal and relish genes were significantly higher among treatment groups, except for the AKP gene in the LCB1 group and the Hsp70 gene in the LCB1.5 group (P < 0.05). Compared with the control, the relative expression levels of TOR, 4E-BP, eIF4E1α and eIF4E2 genes were significantly enhanced in the LCB1.5 group (P < 0.05). When resistance against Vibrio parahaemolyticus in prawn is considered, higher doses of Bovine lactoferricin show better antibacterial ability. The present study indicated that dietary Bovine lactoferricin could significantly improve the growth performance and improve the antioxidative status of M. rosenbergii. The suitable addition level is 1.5 g/kg. LFcinB has great potential as a new feed additive without the threat of drug resistance.

Effects of recombinant anti-lipopolysaccharide factor expressed by Pichia pastoris on the growth performance, immune response and disease resistance of Litopenaeusvannamei

The codon-optimized anti-lipopolysaccharide factor (ALF) sequence was introduced into pPICZαA vector and transformed into Pichia pastoris GS115. The recombinant ALF yeast supernatant (rALF-mix) was freeze-dried and evaluated as a feed additive for Litopenaeus vannamei. It was found by antibacterial activity test in vitro that the rALF-mix had antibacterial activity under different pH and temperature conditions. The 0, 0.00375%, 0.0075%, 0.015%, 0.03% and 0.06% of rALF-mix were added respectively to make the six experimental diets. After a 10-week feeding trial with shrimps (2.36 ± 0.02 g), it was found that the weight gain rate (WGR) and protein efficiency ratio (PER) of shrimp in the groups with 0.0075%, 0.015% and 0.03% of dietary rALF-mix supplementation were significantly higher than those in the control group (P < 0.05). Dietary rALF-mix supplementation significantly increased the total haemocyte count, respiratory burst, phagocytic activity, total anti-oxidative capacity (T-AOC), phenol oxidase activity, nitric oxide synthase activity, lysozyme (LYZ) activity, serum antibacterial capacity in the hemolymph and the T-AOC, LYZ in the hepatopancreas of shrimps (P < 0.05). The malondialdehyde contents in hemolymph and hepatopancreas were significantly decreased (P < 0.05). Meanwhile, the expression levels of toll, immune deficiency, heat shock protein 70, crustin and lipopolysaccharide-β-glucan binding protein in the gill of shrimps were significantly increased (P < 0.05). After the challenge test, it was showed that dietary rALF-mix supplementation significantly improved the resistance of L. vannamei to Vibrio parahaemolyticus (P < 0.05). In conclusion, the rALF-mix can be used as a functional feed additive to improve the growth, immunity and disease resistance of shrimp. Based on the quadratic regression analysis for WGR, the optimal supplemental level of rALF-mix in diet for shrimp was estimated to be 0.02813%.

Dietary Lactoferrin Supplementation Improves Growth Performance and Intestinal Health of Juvenile Orange-Spotted Groupers (Epinephelus coioides)

A 56-day feeding trial was conducted to investigate the effects of dietary lactoferrin (LF) supplementation on the growth performance and intestinal health of juvenile orange-spotted groupers fed high-soybean-meal (SBM) diets. The control diet (FM) and high-soybean-meal diet (SBM60) were prepared to contain 480 g/kg protein and 110 g/kg fat. Three inclusion levels of 2, 6, and 10 g/kg LF were added into the SBM60 to prepare three diets (recorded as LF2, LF6, and LF10, respectively). The results showed that the supplementation of LF in SBM60 increased the growth rate in a dose-dependent manner. However, the feed utilization, hepatosomatic index, whole-body proximate composition, and the abundance and diversity of intestinal microbiota did not vary across the dietary treatments (p > 0.05). After the dietary intervention with LF, the contents of the intestinal malondialdehyde, endotoxin, and d-lactic acid, as well as the plasma low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and total cholesterol were lower, and the intestinal activities of the glutathione peroxidase, lipase, trypsin, and protease were higher in the LF2-LF10 groups than that in the SBM60 group (p < 0.05). The supplementation of LF in SBM60 increased the muscle layer thickness of the middle and distal intestine and the mucosal fold length of the middle intestine vs. the SBM60 diet (p < 0.05). Furthermore, the supplementation of LF in SBM60 resulted in an up-regulation of the mRNA levels for the IL-10 and TGF-β1 genes and a down-regulation of the mRNA levels of the IL-1β, IL-12, IL-8, and TNF-α genes vs. the SBM60 diet (p < 0.05). The above results showed that a dietary LF intervention improves the growth and alleviates soybean meal-induced enteritis in juvenile orange-spotted groupers. The dietary appropriate level of LF was at 5.8 g/kg, through the regression analysis of the percent weight gain against the dietary LF inclusion levels.