Abstract Diet supplementation with essential oil from sweet basil Ocimum basilicum (EOOB) can increase fish growth. So, this study aimed to evaluate the effect of EOOB in the diet on growth ...performance and plasmatic variables of pirarucu juveniles (Arapaima gigas) submitted to stressful condition (stocking density of 7.56 kg m-3per tank and limited space). Four diets (in triplicates) were evaluated with increasing levels of EOOB (0.0 control; 0.5; 1.0; and 2.0 mL kg diet-1) over 48 days. Linalool was the major constituent of EOOB (54.19%). The addition of 2.0 mL EOOB kg diet-1 improved final weight, weight gain, specific growth rate, condition factor and feed conversion ratio; it also decreased plasma urea levels and increased plasma albumin and total proteins levels. Plasma glucose, cortisol, and acid uric levels were not influenced by the addition of EOOB to the fish diet. In conclusion, the addition of 2.0 mL EOOBkg diet-1 is recommended for pirarucu juveniles, due to improved growth performance, and this supplementation did not compromise the homeostasis of fish rearing in a high stocking density.
Abstract The objective of this study was to evaluate the effect of pure glucose, glucose plus fructose, and fructose on the blood glucose of omnivorous fish tambaqui (Colossoma macropomum), Nile ...tilapia (Oreochromis niloticus), piau (Leporinus elongatus), and carnivorous fish hybrid Amazon catfish (Pseudoplatystoma fasciatum × Leiarius marmoratus), pacamã (Lophiosilurus alexandri), and traíra (Hoplias malabaricus). In each species, the dose 1 mL per fish with 1,000 mg kg of body weight-1 of glucose, fructose or glucose plus fructose were tested intraperitoneally. Blood glucose was measured at times 0 (control), 0.5, 1, 2, 4, 8, 16, and 24 h. The administration of 1,000 mg of glucose or glucose plus fructose per kg of live weight causes hyperglycemia in the omnivorous and carnivorous species studied. In the omnivorous species, glycemic levels were reduced from 2 to 4 h, and the regulation to baseline occurred from 4 to 8 h. In the carnivores fish, blood glucose levels declined between 1 and 8 h, and return to baseline was observed from 8 to 16 h. Tambaqui was also intolerant to high concentrations of fructose. Blood glucose levels are regulated in a shorter time in Nile tilapia (mainly), piau and pacamã.
Aims
Aeromonas hydrophila is an opportunistic bacterium, with a high capacity for biofilm production, which can cause severe damage in aquaculture. The objective of this study was to identify the ...chemical compounds of the essential oils of Lippia sidoides (EOLS) and Cymbopogon citratus (EOCC), and to evaluate the biocidal, antibiofilm and synergistic action with the antimicrobial florfenicol of these essential oils (EOs) against A. hydrophila.
Methods and Results
The antibacterial activity of EOLS and EOCC was verified by the minimum bactericidal concentration and by the action of these EOs against both forming and consolidated biofilms. The synergistic activity of EOs with florfenicol was performed using the checkerboard technique. The main component of EOLS and EOCC was carvacrol (44.50%) and α‐citral (73.56%), respectively. Both EOs showed weak inhibitory activity (≥3125.00 µg ml−1). Two bacterial isolates were able to produce biofilm, and EOLS and EOCC acted upon the bacterial isolates to prevent biofilm formation. A bactericidal effect was verified for EOLS in the previously consolidated biofilm for both isolates and for EOCC in only one of the isolates. In general, EOLS had a synergistic effect with florfenicol, while EOCF had an additive effect.
Conclusions
Both EOs were able to interfere with biofilm formation and did not have an antagonistic effect in combination with florfenicol. The best results were found for EOLS, which showed a synergistic effect with florfenicol and the ability to interfere in the formation of consolidated biofilm.
Significance and Impact of the Study
This study highlights the potential of EOLS and EOCC to interfere in biofilm and act in synergy with florfenicol to reduce the occurrence of A. hydrophila. Development of these compounds may contribute to the development of herbal medicines in aquaculture.
Abstract The objective of the present study was to evaluate growth, biochemical, hematological and intestinal enzymes responses and survival of Nile tilapia juveniles fed a diet containing the ...essential oil of lemongrass Cymbopogum flexuosus (EOCF) and infected by Aeromonas hydrophila. Five diets were evaluated (in quadruplicate) with increasing levels of EOCF (0.0 - control; 0.25; 0.50; 1.0 and 2.0 mL kg diet-1). On day 45, eight fish per treatment were sampled and blood, liver and intestine samples were taken. Others eight fish per treatment were infected with A. hydrophila followed by a 15-day period of observation. Citral is the main constituent of EOCF. The inclusion of 2.0 mL EOCF kg diet-1 increased specific growth rate and survival after A. hydrophila infection and decreased feed conversion ratio of Nile tilapia. In general, higher concentrations of EOCF in the diet reduced plasma glucose and triglycerides levels, and increased plasma amino acids, alanine aminotransferase (ALT) and hepatic ALT levels, hematological parameters, and the activity of intestinal enzymes. It was concluded that the inclusion of 2.0 mL EOCF kg diet-1 improved growth performance, biochemical and physiological responses and decreased mortality of Nile tilapia after A. hydrophila infection.
This study aimed to verify the effects of interaction between different temperatures (~18, ~23 and ~ 28°C) with different dissolved oxygen levels (~2.0, ~4.5 and ~ 7.0 mg O2 L‐1) and different ...re‐oxygenation rates (0.5 and 5 hr) after hypoxia in pacu (Piaractus mesopotamicus). In experiment 1, fish were exposed to hypoxia, mild hypoxia or normoxia at low, medium or high temperature for 12 hr. In experiment 2, fish were exposed to hypoxia or normoxia at low, medium or high temperature for 12 hr and, after hypoxia, rapid or gradual re‐oxygenation was performed with a return to normoxia achieved in 0.5 or 5 hr. In experiment 1, blood glucose and pH levels were higher in the hypoxic treatment. The haematocrit and erythrocyte values were lower in mild hypoxia at low and high temperatures respectively. In experiment 2, blood lactate and glucose levels in rapid re‐oxygenation increased after 1 and 12 hr respectively. Twelve hours after rapid re‐oxygenation, haematological values were similar or lower than in the normoxia or gradual re‐oxygenation. In conclusion, exposure of pacu to hypoxic conditions increased blood glucose and pH levels (experiment 1). Additionally, 12 hr after gradual re‐oxygenation, blood variables returned to homeostatic levels (experiment 2).
This study aimed to evaluate the effects of nitrate (NO3–N) in juvenile mullet in freshwater. Experiment 1 evaluated the LC50‐96h of fish at five different NO3–N concentrations (0.01, 85.32, 462.12, ...851.25 and 955.25 mg L−1). Experiment 2 evaluated haematological and oxidative stress variables in fish exposed to four NO3–N concentrations (0.01, 8.16, 33.83 and 52.66 mg L−1) for 5 days. The safe concentration for 96 h was 60.61 mg NO3–N L−1. In experiment 2, blood glucose and haematological values were lower in fish subjected to 52.66 mg NO3–N L−1 compared with the other treatments on day 1. On day 5, fish subjected to the two highest NO3–N concentrations had blood glucose and erythrocytes levels as well as gills and liver ACAP values significantly higher than the control group. Fish exposed to 52.66 mg NO3–N L−1 showed reduced GST activity in gills, liver and muscle on day 5 compared with day 1. In general, exposure to nitrate did not induce an increase in the TBARS levels in the tissues evaluated. In conclusion, acute exposure to 52.66 mg NO3–N L−1 impacted the physiological homeostasis of mullets, but it did not cause lipid peroxidation.
This study evaluated the effect of dietary addition of essential oil from lemongrass (Cymbopogon citratus) (EOCC) on growth, intestinal enzymes, biochemical and haematological variables, and survival ...after Aeromonas hydrophila infection in tambaqui (Colossoma macropomum) juveniles. Five diets with different levels of EOCC—0.0 (control), 0.25, 0.50, 1.00 and 1.50 ml kg diet−1—were evaluated for 60 days, followed by 15 days of bacterial infection. The major chemical compound of EOCC was α‐citral (73.55%). There were no differences in fish survival. Supplementation of 0.25 or 0.50 ml EOCC kg diet−1 increased weight gain (p = 0.034). In general, haematological variables were increased in the treatment 0.25 ml EOCC kg diet−1 (p < 0.05). As the EOCC concentration in the diet increased, plasma glucose, albumin, total cholesterol levels and hepatic somatic index were decreased, and plasma total proteins and muscle glycogen levels were increased (p < 0.05). In tambaqui fed 0.50 ml EOCC kg diet−1, there were increased hepatic glycogen levels (p < 0.016) and intestinal alkaline protease activity (p = 0.049). In conclusion, up to 0.50 ml EOCC kg diet−1 could improve growth performance, haematological variables, muscle glycogen levels and intestinal alkaline protease activity in tambaqui but did not affect fish survival after A. hydrophila infection.
Threonine (Thr) is one of the most limiting amino acids in functional ingredients used for diet preparation, and its deficiency can reduce fish growth. This study aimed to estimate the digestible Thr ...requirement in tambaqui (Colossoma macropomum) diets in the fattening stage for 60 days. Diets containing different digestible Thr concentrations (9.40, 10.30, 11.20, 12.10 and 13.00 g/kg) were analysed. The best results for growth performance, body crude protein content and body deposition occurred in fish fed with 10.30 and 11.20 g Thr kg diet−1 (p < 0.05). The dietary Thr requirement estimated based on weight gain, the feed conversion ratio and the specific growth rate was 10.64, 10.71 and 10.80 g Thr kg diet−1 respectively (p < 0.05). For body deposition, the best values of dietary Thr were between 10.40 and 10.70 g/kg (p < 0.05). Diets with higher levels of digestible Thr caused an increase in plasma cholesterol, liver glycogen levels and erythrocytes, and a decrease in hepatic aspartate aminotransferase levels and mean corpuscular volume (p < 0.05). In conclusion, tambaqui require between 10.40 and 10.80 g Thr kg diet−1 to provide better fish growth performance, body deposition and health.
Abstract This study evaluated the anesthetic activity of essential oil from Lippia alba (EOLA), linalool chemotype in a euryhaline fish (fat snook Centropomus parallelus). In the first experiment, ...fish were exposed to 30, 80, 130, 180, 200, and 230 µL EOLA L−1. The second experiment evaluated smaller and larger fish with 180 µL EOLA L-1. In the third experiment, ventilatory rates (VR) for up to 120 min in animals during exposure to 5 and 10 µL EOLA L−1 were evaluated. In the fourth experiment, fish anesthetized with 30 and 180 µL EOLA L-1 were assessed at 0, 30, and 60 min after anesthesia recovery to evaluate biochemical and antioxidant parameters. The best mild and deep anesthesia times were obtained with 30 and 180 µL EOLA L-1, and larger fish had the highest times. The VR increased in fish exposed to EOLA. Blood glucose and whole-body cortisol levels were higher in fish anesthetized with 180 µL EOLA L-1. Fish exposed to EOLA had higher liver glutathione S-transferase and superoxide dismutase activities without affecting catalase and lipid peroxidation levels. The 180 µL EOLA L-1 is recommended for fat snook anesthesia because it increases VR, blood glucose, and whole-body cortisol levels and prevents oxidative stress.
Resumo Este estudo avaliou a atividade anestésica do óleo essencial de Lippia alba (OELA), quimiotipo linalool, em um peixe eurialino (robalo-peva Centropomus parallelus). No primeiro experimento, peixes foram expostos a 30, 80, 130, 180, 200 e 230 µL OELA L−1. O segundo experimento avaliou peixes pequenos e grandes com 180 µL OELA L-1. No terceiro experimento, avaliou-se taxa ventilatória por até 120 min em animais expostos a 5 e 10 µL OELA L−1. No quarto experimento, peixes anestesiados com 30 e 180 µL OELA L-1 foram avaliados nos tempos 0, 30 e 60 min após a recuperação anestésica para verificação de parâmetros bioquímicos e antioxidantes. Os melhores tempos de anestesia leve e profunda foram obtidos com 30 e 180 µL OELA L-1. Peixes maiores apresentaram anestesia e tempos de recuperação mais elevados. A taxa ventilatória aumentou em peixes expostos para OELA comparados ao grupo controle. Os níveis de glicose sanguínea e cortisol corporal foram maiores em peixes anestesiados com 180 µL OELA L-1. Robalos-peva expostos para OELA tiveram maior atividade de glutationa S-transferase e superóxido dismutase no fígado, sem afetar os níveis de catalase e peroxidação lipídica. O uso de 180 µL OELA L-1 é recomendado para anestesia de robalo-peva, pois aumentou taxa ventilatória e níveis de glicose sanguínea, cortisol corporal, e preveniu estresse oxidativo.
This study assessed the effectiveness of double thermal shock to induce triploidy in tambaqui (Colossoma macropomum) and compared the fertilization, survival, and growth performance of diploid and ...triploid fish. Freshly fertilized eggs were subjected to heat shock (40 or 42°C) for 2 min and, after that, a cold shock (4°C) for 25 min. Eggs that were not exposed to the heat/cold shock were used as control. Ploidy was assessed by flow cytometry. Larvae (21 days after hatching) treated with thermal shocks displayed reduced fertilization and survival rates. The larvae in the 40/4°C and 42/4°C groups displayed higher growth than the control group. The juveniles (135 days after hatching) in the 42/4°C group showed higher growth than the other groups. The 42/4°C shock induced triploidy in 17.5% of nuclei. The double thermal shock 42/4°C did not induce a high rate of triploidization in tambaqui but produced fish with better growth performance.
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