No abstract

Nile tilapia Juveniles (19.50 ± 0.5 g) were fed on a basal diet (control group (CTR)) and a diet supplemented with 1 g Aspergillus oryzae (ASP) per kg diet for 12 weeks. Fish were then subjected to different salinity levels (0, 10, 15, and 20 practical salinity units (psu)) for another 15 days. Two-way ANOVA analysis revealed that the individual effects of ASP in Nile tilapia exposed to salinity levels presented a significant decrease (p < 0.05) in values of haemato-biochemical indices (such as glucose, cortisol, alanine transaminase, aspartate transaminase, and malondialdehyde) compared to those in the CTR group exposed to the same salinity levels. Moreover, significant increases (p < 0.05) of blood protein profile (albumin, globulin, and total protein), non-specific immune responses (lysozyme activity, phagocytic activity, and phagocytic index), and antioxidant enzymes activities (glutathione peroxidase, catalase, and superoxide dismutase) were observed in ASP-supplemented groups. Interestingly, there was significant (p < 0.05) downregulation of the mRNA expression values of heat shock protein 70 and interferon-gamma genes, alongside upregulation of the mRNA expression values of interleukin 1 beta and interleukin 8 genes, in the hepatic tissues of Nile tilapia in ASP-supplemented groups exposed to different salinities compared to those in the CTR group exposed to the same salinity levels. Taken together, these findings supported the potential efficacy of dietary supplementation with ASP in alleviating salinity stress-induced haemato-biochemical alterations, immune suppression, and oxidative stress in the exposed Nile tilapia.

No abstract

Background Fish farming is one of the most productive economies in the world. One of the essential goals in fish production is to minimize processing costs while maintaining and increasing the vital functions, weight and immunity of fish. Objective We conducted this study to explore nanoselenium (Nano‐Se) particles in various feeding schemes. Material and Method Nano‐Se particles incorporated in the basal diet at (0.5 mg/kg diet), and the fish was divided into six groups after adaptation as the follows: The first group was feed daily with a diet containing Nano‐Se (0.5 mg/kg diet); the second group was exposed to a feeding programme in which it has day feeding followed by day of starvation with a diet containing Nano‐Se (0.5 mg/kg diet); the third group was day feeding followed by 2 days of starvation; the fourth group served as a negative control group in which this group was continuous feeding with a basal diet without Nano‐Se; the fifth group was day feeding with the basal diet followed by a day of starvation; and the sixth group was day feeding with basal diet followed by 2 days of starvation. Result Our result revealed that Group 2 showed significant improvement in haematological parameters, red blood cells and haemoglobin with a substantial increase in total protein (p < 0.05) as well as lysosomal and phagocytic activity with considerable upregulation of growth hormone and insulin growth factor 1 in addition to markedly increase in the pro‐inflammatory cytokines. Finally, this study offers the first‐time dietary regime with Nano‐Se supplementation that saves the feeding cost and increases fish welfare and growth.

In the last years, there were some bacterial outbreaks occurred during the summer season of farm-raised Oreochromis niloticus at Kafr El-Sheikh and Dakahlia Governorates resulting in high fish mortalities and severe economic losses in these farms. So, this study aimed to detect the causes of the summer fish mortalities in these governorates to facilitate the diagnosis methods of study pathogens. Thirty fish farms were surveyed (20 in Kafr El-Sheikh and 10 in Dakahlia). 150 examined diseased fish (five from each farm) were succumbed for bacteriological isolation and biochemical and molecular identification. LD 50 experiments were done to detect the infectivity and pathogenicity of some strains of bacterial isolates. The obtained results cleared that O. niloticus summer mortalities were caused by mixed infections with different bacterial species. The isolated bacterial species were 9 types of bacteria; 7 gram negative bacteria; 78 (30.5%) Aeromonas hydrophila, 52 (20.3%) Pseudomonas aeruginosa, 40 (15.6%) Vibrio anguillarum, 20 (7.8%) Edwardsiella tarda, 12 (4.7%) Edwardsiella ictulari, 10 (3.9%) Pseudomonas fluorescens, 7 (2.7%) Flavobacterium columnare and 2 gram positive bacteria; 30 (11.7%) Streptococcus agalactia and 7 (2.8) Enterococcus feacalis which were the most prevalent bacteria affecting fish farms and implicated in the O. niloticus seasonal summer mortalities and LD 50 experiments confirmed the pathogenicity of some isolated bacteria. From the obtained results, it could be concluded that, the main cause of summer fish mortalities in studied farms was 81.82% gram negative bacteria and 18.18% was gram positive bacteria.

Key words:Aeromonas hydrophila, Fingerlings, Oreochromis niloticus, Refeeding, Starvation Knowledge of how fish respond to starvation periods could provide a basis for improved nutrition, rearing, disease control and thereby help to optimize Oreochromis niloticus culture. In the current study, the effect of alternative starvation-refeeding regime was monitored on some growth, hematological and serum biochemical parameters in Nile tilapia fingerlings; followed by checking the role of these feeding schedules in combating the disease challenge. The study was performed in glass aquariums at the aquaculture research unit, Sakha, Kafr El-Sheikh governorate, Egypt using 375 Oreochromis niloticus fingerlings weighing 29±0.5 gram. Fingerlings were subjected to different starvation periods (7, 10, 14, 21 days), followed by 30 days of refeeding on a commercial fish ration (25% protein). Fish growth parameters, hematological and serum biochemical parameters were recorded before starvation, before refeeding and after 30 days of refeeding. The experimental challenge was carried out to determine the effect of different starvation intervals followed by refeeding regimes on the immunity of O. niloticus fingerlings; against bacterial infection with Aeromonas hydrophila through recording mortality rates and the histopathological finding.The collected results revealed that fingerlings can recover all the hematological and serum biochemical parameter values of all food deprived groups close to the normal level of full-fed control fish; concluding that O. niloticus can easily be cultured on suitable economic short-time feeding regime with subsequent refeeding in alternate days without any significant differences in fish size and final production (reducing the food amount and cost required for production cycle). Besides, short-term starvation prior to a bacterial infection followed by subsequent refeeding could promote the defense mechanism of the fish to fight against Aeromonas hydrophila.

The concept of probiotics is widely applied in the field of aquaculture for their beneficial and friendly influences. In this sense, the role of Saccharomyces cerevisiae on the growth, immune and antioxidative responses of European seabass was tested in this study. Fish were distributed in 3 groups (triplicates) with ten fish in each replicate and fed 0, 1, and 2 g/kg of S. cerevisiae (15×109 CFU/g) for 90 days. Fish fed S. cerevisiae showed higher final body, weight gain, and specific growth rate as well as lower FCR than fish fed the basal diet (P<0.05). The RBCs, WBCs, Hb, and PCV values were increased in fish fed dietary S. cerevisiae when compared to the control (P<0.05). The blood total protein, albumin, and globulin were higher in fish fed S. cerevisiae than the control (P<0.05). Fish fed dietary S. cerevisiae had enhanced phagocytic index, phagocytic, and lysozyme activity comparing the control. In a similar sense, the antioxidative enzymes (SOD, GPx, and CAT) were higher in fish fed S. cerevisiae than the control (P<0.05). However, the level of MDA was lowered (P<0.05) by S. cerevisiae in European seabass. Gene expression of IL-8, IL-1β, GH, and IGF-1 was upregulated and HSP70 was downregulated by S. cerevisiae (P<0.05). It can be concluded that European seabass fed S. cerevisiae at 1-2 g/kg (15×109 CFU/g) diet had markedly enhanced growth, haemato-biochemical, and immune performances.

The marine environment is a rich source of bioactive compounds. Therefore, the sea cucumber was isolated from the Red Sea at the Al-Ain Al-Sokhna coast and it was identified as surf redfish (Actinopyga mauritiana). The aqueous extract of the surf redfish was utilized as an ecofriendly, novel and sustainable approach to fabricate zinc oxide nanoparticles (ZnO-NPs). The biosynthesized ZnO-NPs were physico-chemically characterized and evaluated for their possible antibacterial and insecticidal activities. Additionally, their safety in the non-target organism model (Nile tilapia fish) was also investigated. ZnO-NPs were spherical with an average size of 24.69 ± 11.61 nm and had a peak at 350 nm as shown by TEM and UV-Vis, respectively. XRD analysis indicated a crystalline phase of ZnO-NPs with an average size of 21.7 nm. The FTIR pattern showed biological residues from the surf redfish extract, highlighting their potential role in the biosynthesis process. DLS indicated a negative zeta potential (−19.2 mV) of the ZnO-NPs which is a good preliminary indicator for their stability. ZnO-NPs showed larvicidal activity against mosquito Culex pipiens (LC50 = 15.412 ppm and LC90 = 52.745 ppm) and a potent adulticidal effect to the housefly Musca domestica (LD50 = 21.132 ppm and LD90 = 84.930 ppm). Tested concentrations of ZnO-NPs showed strong activity against the 3rd larval instar. Topical assays revealed dose-dependent adulticidal activity against M. domestica after 24 h of treatment with ZnO-NPs. ZnO-NPs presented a wide antibacterial activity against two fish-pathogen bacteria, Pseudomonas aeruginosa and Aeromonas hydrophila. Histopathological and hematological investigations of the non-target organism, Nile tilapia fish exposed to 75–600 ppm ZnO-NPs provide dose-dependent impacts. Overall, data highlighted the potential applications of surf redfish-mediated ZnO-NPs as an effective and safe way to control mosquitoes, houseflies and fish pathogenic bacteria.