Dietary organic acid salts mitigate plant protein induced inflammatory response and improve humoral immunity, antioxidative status and digestive enzyme activities in yellowfin seabream, Acanthopagrus latus

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 %.

Effects of Dietary Lactic Acid Supplementation on the Activity of Digestive and Antioxidant Enzymes, Gene Expressions, and Bacterial Communities in the Intestine of Common Carp, Cyprinus carpio

The present study investigated the effects of dietary lactic acid (LA) supplementation on the growth performance, intestinal digestive/antioxidant enzymes' activities, gene expression, and bacterial communities in common carp, Cyprinus carpio. Four diets were formulated to contain 0 g/kg LA (control), at 2.5 g/kg LA (2.5LAC), 5 g/kg LA (5LAC), and 10 g/kg LA (10LAC) and offered to the fish over a period of 56 days. The results showed that dietary 5 g/kg LA supplementation improved growth performance and feed efficiency in the fish. All LA treatments exhibited significant elevations in the intestinal trypsin and chymotrypsin activities, whereas the intestinal lipase, amylase, and alkaline phosphatase activities exhibited significant elevations in the 5LAC and 10LAC treatments. All LA treatments exhibited significant elevations in the intestinal heat shock protein 70, tumor necrosis factor-alpha, interleukin-1 beta, and defensin gene expressions, and the highest expression was observed in the 5LAC treatment. Additionally, dietary LA treatment significantly increased the lysozyme expression and Lactobacillus sp. population in the intestine of the fish, and the highest values were observed in the 5LAC and 10LAC treatments. Aeromonas sp. and Vibrio sp. populations decreased in the LA treatments, and the lowest Aeromonas sp. population was observed in the 10LAC treatment. The intestinal mucin2 and mucin5 expressions, and the hepatic reduced glutathione content, significantly increased, whereas hepatic glutathione peroxidase, glutathione reductase, and malondialdehyde significantly decreased in the 5LAC and 10LAC treatments. In conclusion, dietary 5 g/kg LA is recommended for common carp feeding to improve growth rate, antioxidant capacity, and intestinal health.

Effects of Replacing Fish Meal with Enzymatic Cottonseed Protein on the Growth Performance, Immunity, Antioxidation, and Intestinal Health of Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

The dietary effects of replacing fish meal with enzymatic cottonseed protein (ECP) on the growth performance, immunity, antioxidant, and intestinal health of Chinese soft-shelled turtles have not been explored. An eight-week feeding trial was conducted with a quadruplicated group of turtles (3.44 ± 0.01 g) that were randomly assigned to 16 cages (0.6 m × 0.6 m × 0.6 m) with 30 turtles that were stocked in each cage. Four dietary groups were fed with diets supplemented with 0, 2%, 4%, and 6% (ECP0 group (control group), ECP2 group, ECP4 group, ECP6 group) of enzymatic cottonseed protein replacing fishmeal. The present study illustrated that the final weight and WG in the ECP2 and ECP4 groups were significantly increased (P < 0.05) compared with the control group. The ECP2, ECP4, and ECP6 groups significantly reduced the feed coefficient (P < 0.05) and significantly increased the SGR (P < 0.05). The serum TP and ALB of the ECP4 group were significantly increased (P < 0.05). The ECP2, ECP4, and ECP6 groups significantly increased the activity of intestinal pepsin (P < 0.05), and the activity of intestinal lipase of the EPC4 group was significantly increased (P < 0.05). The intestinal villus height of the EPC4 group and EPC6 group, the villus width of the EPC2 group and EPC4 group, and the intestinal muscle thickness of the EPC4 group were significantly increased (P < 0.05). At the same time, replacing fishmeal with enzymatic cottonseed protein also affected the intestinal inflammation-related genes compared with the control group. Besides that, the expression of the IL-10 gene in the experimental group was significantly upregulated (P < 0.05). Nevertheless, the expression of TNF-α and IL-8 genes in the ECP2 group and TNF-α and IL-1β genes in the ECP4 group was significantly downregulated (P < 0.05). In summary, replacing fish meal with enzymatic cottonseed protein positively affects the growth, immunity, and intestinal health of Chinese soft-shelled turtles. The appropriate proportion of enzymatic cottonseed protein to replace fish meal in turtle feed is 4%.

Dietary powder and molecular imprinted polymer nanoencapsulated sodium propionate to enhance growth performance, digestive enzymes activity, antioxidant defense, and mucosal immune response in African cichlid (Labidochromis lividus) fingerlings

This study was conducted to examine the effects of powder sodium propionate (P-SP) and SP-loaded molecular imprinted polymer (MIP) nanoparticles (MIP-SP NPs) on the growth, skin mucosal immune parameters, and digestive and liver enzymes activities of African cichlid (Labidochromis lividus) fingerlings. Fish with an average weight of 500±2 mg were stocked into 12 experimental units and fed on experimental diets prepared by supplementing the basal diet (control) with MIP NPs, P-SP (5 g SP Kg-1 of dry diet), and MIP-SP NPs for 8 weeks. The findings demonstrated that growth indices improved in the MIP-SP NPs followed by the P-SP dietary group compared to the control groups (P<0.05). The activity of digestive enzymes of lipase, trypsin, protease, and alkaline phosphatase was higher in the fish fed SP-supplemented diets than in the controls (P<0.05). The protease and lipase activities in the MIP-SP NPs dietary group increased by 29.33% and 48.81% compared to the control, respectively (P<0.05). In addition, the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels of liver tissue decreased in the SP dietary groups, while the catalase (CAT), superoxide dismutase (SOD), and alkaline phosphatase (ALP) levels increased compared to the control groups (P<0.05). The highest SOD and ALP levels were observed in the fish fed on the MIP-SP NPs-supplemented diet (P<0.05). Furthermore, the skin mucosal immune indices including, alternative haemolytic complement activity (ACH50), lysozyme, and total immunoglobulin (Ig) levels increased in the MIP-SP NPs and P-SP dietary groups compared to the controls (P<0.05). The findings indicated that sodium propionate encapsulated in molecularly imprinted polymer nanoparticles could enhance the efficiency of dietary SP in African cichlid fish.

Proteomics reveals multiple effects of titanium dioxide and silver nanoparticles in the metabolism of turbot, Scophthalmus maximus

Titanium dioxide (TiO₂) and silver (Ag) NPs are among the most used engineered inorganic nanoparticles (NPs); however, their potential effects to marine demersal fish species, are not fully understood. Therefore, this study aimed to assess the proteomic alterations induced by sub-lethal concentrations citrate-coated 25 nm ("P25") TiO₂ or polyvinylpyrrolidone (PVP) coated 15 nm Ag NPs to turbot, Scophthalmus maximus. Juvenile fish were exposed to the NPs through daily feeding for 14 days. The tested concentrations were 0, 0.75 or 1.5 mg of each NPs per kg of fish per day. The determination of NPs, Titanium and Ag levels (sp-ICP-MS/ICP-MS) and histological alterations (Transmission Electron Microscopy) supported proteomic analysis performed in the liver and kidney. Proteomic sample preparation procedure (SP3) was followed by LC-MS/MS. Label-free MS quantification methods were employed to assess differences in protein expression. Functional analysis was performed using STRING web-tool. KEGG Gene Ontology suggested terms were discussed and potential biomarkers of exposure were proposed. Overall, data shows that liver accumulated more elements than kidney, presented more histological alterations (lipid droplets counts and size) and proteomic alterations. The Differentially Expressed Proteins (DEPs) were higher in Ag NPs trial. The functional analysis revealed that both NPs caused enrichment of proteins related to generic processes (metabolic pathways). Ag NPs also affected protein synthesis and nucleic acid transcription, among other processes. Proteins related to thyroid hormone transport (Serpina7) and calcium ion binding (FAT2) were suggested as biomarkers of TiO₂ NPs in liver. For Ag NPs, in kidney (and at a lower degree in liver) proteins related with metabolic activity, metabolism of exogenous substances and oxidative stress (e.g.: NADH dehydrogenase and Cytochrome P450) were suggested as potential biomarkers. Data suggests adverse effects in turbot after medium/long-term exposures and the need for additional studies to validate specific biological applications of these NPs.

Modulation of humoral immunological and antioxidant responses and gut bacterial community and gene expression in rainbow trout, Oncorhynchus mykiss, by dietary lactic acid supplementation

The present study was conducted to find the effects of dietary lactic acid (LA) supplementation on growth performance, hematological characteristics, humoral antioxidant and immunological factors, intestinal gene expression and bacteriological parameters in rainbow trout, Oncorhynchus mykiss. The fish (104 ± 0.90 g) were randomly distributed in twelve tanks (150 L water) as four treatments, receiving diets supplemented with 0, 5, 10, and 20 g/kg LA for 70 days. At the end of the feeding trial, no significant differences were observed in the fish growth performance and survival among the treatments. Blood/plasma red blood cell (5-20 g/kg LA), white blood cell (10 g/kg LA), hematocrit (5 and 10 g/kg LA), hemoglobin (5 and 10 g/kg LA), superoxide dismutase (10 g/kg LA), glutathione peroxidase (10 g/kg LA), total antioxidant capacity (10 g/kg LA), lysozyme (5-20 g/kg LA), and alternative complement activity (10 g/kg LA) significantly increased, as malondialdehyde (10 g/kg LA) significantly decreased in the LA-treated fish. Dietary LA supplementation induced no significant changes in the intestinal defensin gene expression, but significantly up-regulated the expression of toll-like receptor-3 (5-20 g/kg LA), Mx-9 (5-20 g/kg LA), and heat shock protein-70 (5 g/kg LA) genes; the highest expressions were observed at 5 g/kg LA supplementation. Dietary LA supplementation significantly increased total bacterial count (5 and 10 g/kg LA), Lactobacillus sp. (5-20 g/kg LA), and Bacteroides sp. (5-20 g/kg LA), but decreased Streptococcus iniae (5-20 g/kg LA) in the fish intestine; the highest Lactobacillus sp. And Bacteroides sp. Were observed in 10 and 5 g/kg LA supplementation, respectively. Overall, dietary LA supplementation, although has no significant effects on the fish growth performance, is beneficial to improve humoral antioxidant parameters, humoral and intestinal immunological parameters and intestinal microflora. According to the results, dietary 5-10 g/kg LA is recommended for the formulation of rainbow trout feed.

The Combined Effects of Propionic Acid and a Mixture of Bacillus spp. Probiotic in a Plant Protein-Rich Diet on Growth, Digestive Enzyme Activities, Antioxidant Capacity, and Immune-Related Genes mRNA Transcript Abundance in Lates calcarifer Fry

A 7-week feeding trial was conducted to evaluate the combined effects of propionic acid (PA, 5 or 10 g/kg) and a multi-strain Bacillus spp. (Bacillus subtilis IS02 (accession no. JN856456) and B. licheniformis IBRC-M 11,319) (1.7 × 10⁷ CFU/g) probiotic in a plant protein source (PP)-rich diet (∼70% of dietary protein derived from PP sources) on performance of Asian sea bass (Lates calcarifer) fry (initial body weight 2.97 ± 0.11 g). In this regard, six isoproteic (∼48%) diets were formulated as follows: a control (without supplementation of the additives); probiotic (only contained Bacillus spp. mixture); 5 g PA/kg diet; 10 g PA/kg diet; probiotic + 5 g PA/kg diet, and probiotic + 10 g PA/kg diet. Specific growth rate in fish fed with 10 g PA/kg (2.84 ± 0.1%) and diets contained blends of probiotic and PA (2.76 ± 0.19% in probiotic + 5 g PA, and 2.79 ± 0.04% in probiotic + 10 g PA) was better than in the control (2.45 ± 0.1%) (P < 0.05). Feed conversion ratio in fish fed with 10 g PA/kg (0.92 ± 0.12) and diets contained blends of probiotic and PA (0.94 ± 0.06 in probiotic + 5 g PA and 0.91 ± 0.02 in probiotic + 10 g PA) was better than in the control (1.24 ± 0.08) (P < 0.05). Digestive enzymes including α-amylase, total alkaline proteases, and bile salt dependent lipase activities improved in fish fed diets contained additives. The activity of glutathione-S-transferase and glutathione reductase enhanced in the liver of fish fed diets contained additives. The relative abundance of lysozyme, interleukin 1β, and insulin-like growth factor-1 genes mRNA transcript showed multifold increase in the liver of fish fed with the 10 g PA/kg and diets contained blends of probiotic and PA (P < 0.05). By considering the above mentioned results, supplementing a PP-rich diet with 10 g PA/kg diet or combination of PA and a mixture of Bacillus spp. probiotic recommended for L. calcarifer.

Blood Performance: A New Formula for Fish Growth and Health

Simple Summary

The use of haematological and blood biochemistry parameters has proven to be effective and repeatable ways to monitor fish health. Testing these parameters is becoming more common in aquaculture studies. Further, it is widely accepted that fish with better health status are more likely to grow faster as less energy should be consumed for non-growth purposes. Here, a new formula (Blood Performance) is introduced, which contains five common haematological and blood biochemistry parameters: red blood cells, white blood cells, haemoglobin, haematocrit, and total protein. The idea behind this formula is that any single component of this formula cannot be reliable enough as a biomarker of fish health and growth. However, interestingly, Blood Performance can be much more reliable and accurate for monitoring fish health and growth.

Abstract

Monitoring fish health in a repeatable and accurate manner can contribute to the profitability and sustainability of aquaculture. Haematological and blood biochemistry parameters have been powerful tools and becoming increasingly common in aquaculture studies. Fish growth is closely related to its health status. A fish with a higher growth rate is more likely to be a healthy one. Any change in the physiological status of the fish, from pollution to nutritional stress, can cause changes in the blood parameters. Various aquaculture studies have measured the following components: red blood cells, white blood cells, haemoglobin, haematocrit, and total protein. However, because these parameters do not always follow the same trend across experimental fish, it is difficult to draw a firm conclusion about which parameter should be considered. Therefore, Blood Performance (BP) as a new formula is introduced, which is a more reliable indicator. This formula is simple and sums up the natural logarithm of the five above-mentioned parameters. More than 90 published peer-reviewed articles that measured these five parameters in the last six years confirmed the reliability and validity of this formula. Regardless of which supplements were added to the diets, the fish with a higher growth rate had higher BP as well. In addition, in 44 studies out of 53 articles, there was a significant positive correlation between specific growth rate and BP. Under different stressful situations, from pollution to thermal stress, the fish under stress had a lower BP than the control. Fish meal and fish oil replacement studies were further evidence for this formula and showed that adding excessive alternative proteins decreased growth along with BP. In conclusion, BP can be a reliable indicator of fish health and growth when it is compared between groups in the same experiment or farm. Although there was a positive correlation between specific growth rate and BP, comparing BP between experiments is not recommended. Standardising the haematological assays can improve the reliability and accuracy of BP across experiments.