Background: The current study was conducted to prepare an efficient super-paramagnetic iron oxide nanoparticle (SPIONs) to remove Aeromonas hydrophila from water. Methods: The nanoparticles were synthesized by the co-precipitation method and characterized by DLS, UV-Vis spectrophotometer, FT-IR, XRD, FEG-TEM, and VSM analysis. Results and Discussion: The results showed that the synthesized SPIONs were having a size range of 8-12nm with magnetic property. Bacteria removal efficiency and antibacterial activity of SPIONs were assessed in sterile distilled water by adding different concentrations of SPIONs viz. 0, 6.25, 12.5, 25, 50, 100, 200, 500, and 1000µM with different initial bacterial loads viz. 1×103, 1×104, 1×105, 1×106, and 1×107 CFU mL−1 at different time intervals 15, 30, 45, and 60 min. At low bacterial load (1×103 to 1×105 CFU mL−1), 95 to 99.99% of bacteria were removed by low SPIONs concentration (6.25-100µM) by 15min which was increased up to 100% by 30min. However, at high bacterial load (1×106 to 1×107 CFU mL−1), more than 87 to 95% of bacteria were removed by the highest SPIONs concentration (1000µM) by 15min, which was increased above 93 to 99.99% by increasing the exposure time to 60min. At low bacterial load (1×103 to1×105 CFU mL−1), the effective concentration was 3.21 to 6.42µM at 15-60 min intervals. Meanwhile, the effective concentration at high bacterial load was 267.81 µM at 15min, which was decreased to 104.09 µM with increasing exposure time to 60min. Conclusion: Based on the results, it is concluded that the antibacterial effect against A. hydrophila depends on the concentration as well as the exposure time of SPIONs. A low concentration of SPIONs is sufficient to remove 100% of bacterial load in lower exposure time and increasing concentration of SPIONs increases the antibacterial effect. However, further research requires to find the safe concentration of SPIONs for using it as a novel antibacterial agent for the treatment of aeromonads disease in aquaculture.

A 60‐day feeding trial was conducted to evaluate the effect of dietary protein level on growth, digestive enzymes and haemato‐biochemical responses of Penaeus vannamei juveniles in inland ground saline water (IGSW) of 15 ppt salinity. The acclimated shrimp (avge. wt., 4.03 ± 0.05 g) were randomly distributed into seven groups, viz. TCP20, TCP25, TCP30, TCP35, TCP40, TCP45 and TCP50, in triplicate with the stocking density of 15 shrimp per tank (275 L). Seven semi‐purified hetero‐nitrogenous (200–500 g crude protein/kg), iso‐caloric (396 Kcal DE/100 g) and iso‐lipidic (60 g/kg) diets were prepared for feeding the shrimp of respective group four times daily on satiation basis. Results indicated that the highest (p < 0.05) WG and SGR, and the lowest FCR were observed in TCP40 group. But PER and ANPU values decreased significantly (p < 0.05) with increasing dietary protein. Whole‐body protein and ash contents varied significantly (p < 0.05) with an inverse relationship. Shrimps of TCP40 group had the highest (p < 0.05) haemocyanin and serum total protein, while TCP20 group showed the highest (p < 0.05) serum glucose. Serum cholesterol and triglyceride increased significantly (p < 0.05) with increasing dietary protein level up to 400 g protein/kg and beyond that these decreased gradually. Protease activity increased with increasing dietary protein level, but amylase activity showed an inverse trend. Second‐order polynomial regression analysis in relation to WG, SGR and FCR indicated that 393.0–397.90 g protein/kg diet could be optimum for culture of P. vannamei juveniles in IGSW of 15 ppt salinity.

The study was conducted to investigate the efficacy and physio-metabolic responses of single and multiple doses of fenbendazole (FBZ) in Labeo rohita against gill parasite (Dacylogyrus sp.). Two Isoenergetic (395 Kcal DE/100 g) and isonitrogenous (35% CP) purified diets viz. control (without FBZ) and treatment (0.2% FBZ) were prepared. The efficacy of FBZ was measured after administration of single dose (20 mg/kg b. wt.) on 0th day and multiple doses of FBZ, that is, 20 mg/kg b. wt. on 0th, 3rd and 7th day through diet. Although oral administration of FBZ at single dose could significantly reduce the parasite in fish in comparison with the control group, 100% efficacy of the drug was not achieved up to 15th day of treatment. On the other hand, multiple doses of FBZ could show almost 100% efficacy on 15th day in terms of elimination of parasites from gill. The drug induced oxidative stress in examined fish. There was no significant change in activities of hepatic and muscle aspartate aminotransferase and alanine aminotransferase of L. rohita up to 15th day after oral administration of FBZ at single dose. But both single and multiple doses of FBZ could significantly enhance the hepatic superoxide dismutase, catalase and glutathione-S-transferase activities in fish up to 7th day of drug administration and significantly decreased thereafter up to 15th and/or 30th day. It is concluded that oral administration of FBZ at multiple doses (20 mg/kg b. wt.) on 1st, 3rd and 7th day could be effective against Dactylogyrus sp. infection in L. rohita. K E Y W O R D S Dactylogyrus, efficacy, fenbendazole, Labeo rohita, parasite | 1191 GUPTA eT Al.

A feeding trial was conducted with inclusion levels of Cajanus cajan leafmeal (CCLM) in the diet of Labeo rohita to study the growth, haematological indices, digestive enzyme, physio‐metabolic changes and molecular expression of insulin‐like growth factor‐1 (IGF‐1), insulin‐like growth factor‐binding protein‐1 (IGFBP‐1), insulin‐like growth factor‐1 receptor (IGF‐1R) genes. Four practical diets with CCLM, control, T20 (20%), T30 (30%) and T40 (40%) were prepared. Weight gain%, SGR, FER and PER were significantly (p < 0.05) higher when 30% de‐oiled rice bran (DORB) was replaced by CCLM whereas the treatment group 40% registered with lower FCR value. The protease and amylase activities were higher in the T30 group. T20 showed significantly higher (p < 0.05) hepatic and muscular lactate dehydrogenase and serum glucose was also higher, whereas, WBC content was found significantly (p < 0.05) higher in control. The hepatic IGF‐1 gene expression was significantly higher (p < 0.05) in T40 followed by the T30 group but the weight gain was not significantly (p > 0.05) higher in T30 from the T40 group. Results reveal that the response of IGF‐1, IGF‐1R and IGFBP‐1 genes was complementary to the biological growth parameters and hence were used as an indicator to evaluating growth. The study also demonstrates that CCLM can replace 100% DORB in the diet of L. rohita without any antinutritional or adverse growth effects.

The availability of zinc has been correlated with reproductive performance. To validate the hypothesis, a 60‐day feeding trial was conducted to evaluate the effect of dietary zinc on reproductive performance and gonadotropin gene (FSH and LH) expression in threatened Clarias magur brooder. Four isonitrogenous (35%) and iso‐energetic (372.18 ± 1.73 k cal/100 g) diets were prepared with zinc acetate as control (100 mg/kg diet normal requirement), T1 (50 mg/kg diet, low zinc), T2 (200 mg/kg diet, medium zinc) and T3 (300 mg/kg diet, high zinc). The weight gain % and specific growth rate were significantly (p < 0.05) decreased with the increased dietary zinc level. The pituitary mRNA levels of FSH were assessed during the reproductive cycle of female C. magur, and the FSH expression was increased which was significantly (p < 0.05) highest in T1 group. Similarly, LH expression was revealed to be highest. In all treatment groups except T1, GTH expression reduced significantly by increasing zinc inclusion in the diet. GSI and fecundity were lowest during initial sampling and start to increase was observed. The highest GSI and fecundity were recorded in the T1; however, GSI and fecundity significantly (p < 0.05) reduced with increasing the zinc level. Reproductive parameters like spawning fecundity, fertilization rate, hatching rate and larval survival were found to be dose‐dependent of zinc. This revealed that 50 mg/kg zinc was optimum for enhanced reproductive performance; therefore, the present study proposed that 50 mg/kg of zinc could be supplemented for flexible enhanced reproductive performance in threatened Asian catfish, C. magur.