Juvenile Nile Tilapia Research Articles

Different levels of organic trace minerals in diets for Nile tilapia juveniles alter gut characteristics and body composition, but not growth

Different levels of organic trace minerals in diets for Nile tilapia juveniles alter gut characteristics and body composition, but not growth

Combined effects of dietary starch:Protein ratios and short cycles of fasting/refeeding on Nile tilapia growth and liver health

This study evaluated the combined effects of different dietary starch:protein ratios (SPR) and short cycles of fasting/refeeding (FR) on Nile tilapia juveniles on growth, feed and nutrient use, whole-body composition and liver health. Three diets with SPR classified as high (S30:P32; 0.96 g:g), intermediate (S25:P36; 0.69 g:g) and low (S21:P39; 0.53 g:g) were fed to fish over 60 days on three feeding regimes: 0FR—fish fed daily (control treatment); 1 FR—fish fasted for one day and refed for three days and 2 FR—fish fasted for two days and refed for three days. Fish (2.25 ± 0.01 g) were allotted to a completely randomized factorial design (3 × 3; n = 3). Fish growth and feed conversion ratio decreased (p < .05) with increasing FR. There was no significant difference in daily feed intake between regular-fed and fasted tilapia as a consequence of hyperphagia in fasted fish. Protein and energy productive values increased (p < .05) with increasing SPR. The occurrence of hepatic steatosis was similar (p > .05) among daily-fed fish regardless of SPR but increased (p < .05) with increasing SPR in fasted fish. Regardless of dietary SPR, short cycles of fasting/refeeding do not promote compensatory growth. Therefore, Nile tilapia around 2g should be fed daily with low-SPR diet.

Poultry byproducts and swine liver used in diets for Nile tilapia juveniles

This study aimed at evaluating diets containing protein hydrolysate from poultry byproducts and swine liver (PHPPL), at different inclusion levels, for Nile tilapia (Oreochromis niloticus) juveniles. Seven diets were evaluated, being a negative control (free of both hydrolysate and fishmeal) and positive control (free of hydrolysate but containing fishmeal), besides five diets with 1, 2, 3, 4, or 5% inclusion of the mixed protein hydrolysate. Significant effects were observed regarding the animals' final length, with higher values with the 1% inclusion level than the negative control. The liver's quantitative evaluation revealed that inclusions above 3% might lead to severe alterations in the organ's morphology. The use of PHPPL in the diets that did not contain fishmeal has shown to be effective in maintaining the performance parameters of Nile tilapia. Thus, its use is recommended considering an inclusion level of 3%.

Growth Performance, Nutrient Digestibility, Hematological Parameters, and Hepatic Oxidative Stress Response in Juvenile Nile Tilapia, Oreochromis niloticus, Fed Carbohydrates of Different Complexities.

Simple SummaryProteins are the highest-cost nutrients of aquafeed and are the essential components in diets and, thus, are acknowledged as the most critical input in aquafeed. The utilization of alternative sources to prepare cheaper feed is requisite to ensure the sustainability of the aquaculture sector. Carbohydrates are the least-expensive form of energy source in practical diet ingredients, more available than proteins, and efficiently used by omnivorous warm-water fishes. The use of carbohydrate-based diets has the advantage of being economically efficient, owing that fish would efficiency utilize the low-cost carbohydrate. Factors that affect the carbohydrate utilization efficiency are carbohydrate origin, dietary level, physical state, technological treatments, and molecular complexity. Also, they can adversely affect fish health through metabolic disorder and physio-clinical signs such as hyperglycemia, increment of glycogen deposition, liver hypertrophy, and histopathological development. Physiological and biochemical characteristics are recognized as a useful tool in the evaluation of the metabolic functions, health status and welfare of farmed species. With reference to our study, knowledge of the physiological and health implication of dietary carbohydrate helps fish nutritionists to tailor and improve the nutritional profile of the diet and hence to provide more adequate and healthy diets for fish.A 45-day feeding trial was conducted to assess the capacity of juvenile Nile tilapia (2.12 ± 0.02 g) to utilize different sources of carbohydrate in their diets. Growth performance, nutrient digestibility, hematological parameters, and hepatic oxidative stress were evaluated. Four experimental diets were formulated to be isonitrogenous (25% crude protein) and isolipidic (10% crude lipid), each containing 20% glucose (GLU-diet), maltose (MAL-diet), dextrin (DEX-diet), and corn starch (CST-diet), respectively. At the end of feeding trial, survival in all groups was above 90% and was not significantly different among groups. The results indicated that fish fed the DEX-diet and CSTA-diet showed significantly (p < 0.05) better specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) compared with those fed the other diets. The dry matter and carbohydrate digestibility were significantly higher (p < 0.05) in groups fed on dextrin and corn starch diets. However, the digestibility of crude protein and energy in diets did not differ significantly (p > 0.05) among groups fed on experimental diets. The activities of analyzed antioxidant enzymes in the liver were significantly (p < 0.01) higher in groups fed on glucose and maltose diets when compared to other groups. Hematological parameters were affected by the dietary carbohydrate sources; there was a significant increase in hematocrit (Ht), hemoglobin (Hb), and mean corpuscular volume (CMV) in the blood of fish fed on dextrin and cornstarch diets compared to other experimental diets. These results indicated that low complexity carbohydrate sources induced oxidative stress and depressed growth performance. Overall, these results indicate that dietary dextrin and starch were more efficiently utilized than glucose as an energy source by juvenile Nile tilapia. This information is of increasing interest in fish nutrition to provide healthy and economically feed formulations.

The effects of açaí oil addition in tilapia diets on performance, hepatic energy metabolism enzymes and antioxidant responses

The aim of the present study was to determine whether açai oil (Euterpe oleraceae) addition in the diets of juvenile Nile tilapia (Oreochromis niloticus) in biofloc system would stimulate hepatic energy metabolism and antioxidant responses. Treatments are as follows: T0 (6%-soybean oil), T1 (1%-AÇAI; 5%-SOY), T3 (3% AÇAI; 3%-SOY) and T6 (6%-AÇAI). In the liver, reactive oxygen species levels were significantly lower in T1, T3 and T6 than in T0, lipid peroxidation levels were significantly lower in T3 and T6, and nitric oxide levels were significantly lower in the T6 than in T0. Glutathione peroxidase activity was significantly higher in the T3 and T6 than in T0, while superoxide dismutase activity and total antioxidant capacity levels were significantly higher in the T6 than in T0. Adenylate kinase activity was significantly lower in the T6 than in T0. These results suggest that the açai oil addition in Nile tilapia diets stimulated antioxidant responses.

Effects of dietary Nannochloropsis oculata on growth performance, serum biochemical parameters, immune responses, and resistance against Aeromonas veronii challenge in Nile tilapia (Oreochromis niloticus)

The current work was planned to assess the effects of dietary microalga, Nannochloropsis oculata (NP) on the growth indices, serum biochemistry, non-specific immunity, and resistance of Nile tilapia (Oreochromis niloticus) juveniles against challenge with pathogenic Aeromonas veronii. Fish (10.21 ± 0.28 g) were randomly divided into four treatments in triplicates and were fed on diets supplemented with different levels of NP (0, 5, 10, and 15%) for eight weeks. The results showed that the dietary 5% NP significantly improved the growth parameters (final body weight, weight gain, specific growth rate, and total feed intake) (P < 0.05). Meanwhile, the feed conversion ratio was significantly decreased in NP-supplemented groups with respect to the control group. The serum protein profile (total protein, albumin, globulin, and albumin/globulin ratio) was significantly decreased by 15% NP supplemented group. Meanwhile, liver enzymes (alanine transaminase, and aspartate transaminase) activities were not significantly affected by NP dietary supplementation (P < 0.05). Serum lysozyme activity, nitric oxide (NO), and nitroblue tetrazolium (NBT) levels were significantly enhanced only in 5% NP supplemented group (P < 0.05). Interestingly, the hepatopancreatic and intestinal tissues had apparently normal histomorphology of Nile tilapia fed at 5% NP-supplemented diets. Significant upregulation of cytokines [interleukin 1beta (IL-1β), interleukin 8 (IL-8), interferon-gamma (IFN-γ), transforming growth factor-beta (TGF- β), and tumor necrosis factor-alpha (TNF-α)], with significant downregulation of the antioxidant gene [superoxide dismutase (SOD)] in 10% and 15% NP supplemented groups. Attractively, the relative level of protection (RLP) against challenge with pathogenic A. veronii was significantly elevated in 10% and 15% NP supplemented groups. Conclusively, the obtained results reflect the beneficial roles of dietary NP to improve growth and boost the immune responses of Nile tilapia.

The effects of four plant extracts on growth, sex reversal, immunological and haemato‐biochemical parameters in Nile tilapia,Oreochmomis niloticus(Linnaeus, 1758)

Growth and immune status of monosex Nile tilapia produced through dietary treatment with solvent extracts of four plant materials were analysed. Nile tilapia juveniles (mean weight 0.025 ± 0.009g) were fed diet containing 17α-methyltestosterone (10 mg/kg feed, MT), Basella alba leaf ethanol extract (1.0 g/kg feed, EB), Tribulus terrestris seed ethanol extract (2.0 g/kg feed, ET), Mucuna pruriens seed methanol extract (0.2 g/kg feed, MM), Asparagus racemosus root methanol extract (0.2 g/kg feed, MA) for 30 days followed by basal diet for 90 days. The control group was fed basal diet for 120 days. MT, EB, ET and MA showed significantly (p < .05) higher male (%), final weight (g), final length (mm), weight gain (g), specific growth rate (%) compared with control and MM. EB and MA showed significantly (p < .05) better immunostimulatory (phagocytic, lysozyme activities, respiratory burst), haematological, antioxidant and hepatoprotective activity compared with other treatment groups. MT, EB, ET and MA showed significantly (p < .05) higher level of GH, IGF-1 and 11-KT compared with control and MM. The growth and health promoting, and immunostimulating efficacy of plant extracts may be attributed to the presence of steroidal saponins and polyphenols in them. EB and MA were more potent in growth promotion, immunostimulation and adaptogenic potential compared with other two plant materials. These two plant materials may be used as an environment friendly safe alternative to MT for production and culture of monosex Nile tilapia.

Integrated production of Nile tilapia juveniles and lettuce using biofloc technology

The aim of the present study was to evaluate the use of the technology we have named for the first time as FLOCponics (biofloc + hydroponic) (FP) and conventional aquaponics (AP) systems in producing Nile tilapia (Oreochromis niloticus) juveniles and lettuce (Lactuca sativa). The experiment was carried out for 46 days and consisted of two cycles of lettuce production (23 days each) and one cycle of juvenile production. The physical–chemical variables of the water, zootechnical performance of the fish, growth performance and visual characteristics of the plants, nutrient dynamics, and characterization of the planktonic community were evaluated in both systems. The results showed better fish productive performance in FP, with a mean final weight of 36.7 g compared with 34.9 g in AP. For plants, the Cycle 2 in the AP system showed the best plant growth and visual results (98% of the plants received the highest scores—grades A (excellent) and B (good)—on the plant quality index), whereas in FP only 37% achieved these grades in the same cycle. The results suggest that the integrated production of tilapia juveniles and lettuce using FP might be technically feasible if specific fertilization management or mechanisms are developed to refine the critical points of the system (e.g., nutrient imbalance and solids accumulation in the plant roots) to improve plant production.

Chronic effects of a binary insecticide Acer 35 EC on Nile tilapia Oreochromis niloticus through a multi-biomarker approach

Acer 35 EC is a widely used insecticide (a binary mixture of lambda-cyhalothrin and acetamiprid) in pest control in many West African countries, particularly in the cotton culture in north Benin. The aim of this study was to investigate the chronic effects of Acer 35 EC on Nile tilapia Oreochromis niloticus juveniles using a multi-biomarker approach under laboratory conditions. For this purpose, fish were exposed to sublethal concentrations of Acer 35 EC (0, 1 and 10% of LC50- 96 h value). After 28 and 56 days of exposure, several biomarkers were measured in males and females including enzymatic activities related to detoxification and oxidative stress, neurotoxicity and immune responses, sex steroid hormones (testosterone, 17β-estradiol and 11-keto-testosterone) and histological alterations of liver, kidney and gonads. An Integrated Biomarker Response (IBR) was then calculated. The results showed a reduction of cholinesterase activity in muscles, and intercellular superoxide anion production in both sexes. Female steroidogenesis and gametogenesis were affected, especially testosterone levels and oocyte growth. More alterations were observed in liver after exposure to Acer 35 EC. In both sexes, IBR values were higher after 56 days than after 28 days of exposure. In conclusion, based on a large set of biomarkers and IBR values, the chronic exposure to low doses of insecticide Acer 35 EC seems to impair different physiological functions in Nile tilapia juveniles on a time-dependent manner, with a stronger impact on females than on males.

Mannanoligosaccharides as a Carbon Source in Biofloc Boost Dietary Plant Protein and Water Quality, Growth, Immunity and Aeromonas hydrophila Resistance in Nile Tilapia (Oreochromis niloticus).

The aim of the present study was to evaluate mannan oligosaccharides (MOS) or glycerol (GLY) as a carbon source on biofloc systems of Nile tilapia (O. niloticus) juveniles. Fish (n = 750) were reared in open flow (Controls) or biofloc systems (B-GLY and B-MOS) fed with a plant or fish protein source over a period of twelve weeks. Total ammonia nitrogen and nitrate decreased in the biofloc groups, while biofloc volume increased in B-MOS. Compared to the controls, B-MOS and B-GLY exhibited higher weight gain and improved feed conversion, irrespectively of the diet. Serum level of C-reactive protein was reduced, while IgM and lysozyme activity was higher in the B-MOS fish, compared to other groups. Intestinal Bacillus spp. count was increased, whereas Vibrio, Aeromonas and Pseudomonas spp. counts decreased in B-MOS reared groups, compared to the other groups. The proinflammatory cytokine (IL-8 and IFN-γ) transcript expression was upregulated in B-MOS more than B-GLY reared groups. Compared to the controls, the virulence of Aeromonas hydrophila was decreased in the B-MOS and B-GLY groups. The results indicate several benefits of using MOS as a carbon source in a biofloc Nile tilapia system; a cost benefit analysis is required to assess the economic viability of this.

Oregano (Origanum vulgare), St John's-wort (Hypericum perforatum), and lemon balm (Melissa officinalis) extracts improved the growth rate, antioxidative, and immunological responses in Nile tilapia (Oreochromis niloticus) infected with Aeromonas hydrophila

The present study was designed to evaluate the effects of ethanolic extracts of Hypericum perforatum (HP), Origanum vulgare (ORG), and Melissa officinalis (MOF) on Nile tilapia (Oreochromis niloticus) juveniles. Fish (16.92 ± 0.28 g) were randomly divided into seven groups fed on diets with 0 % (CTR), and two levels (0.2 % and 0.5 %) from each plant extract for 60 days. Final body weight, weight gain %, specific growth rate, and feed conversion ratio were significantly improved in the groups fed with ORG and MOF at 0.5 % (P < 0.05). Moreover, ORG 0.5 % and MOF 0.5 % groups showed a significant increase in RBCs and WBCs counts as well as the hematocrit and hemoglobin values (P < 0.05). Besides, significant enhancement was noticed in the levels of intestinal digestive enzymes in the MOF 0.5 % group (P < 0.05). Activities of hepatic superoxide dismutase, glutathione peroxidase, catalase were significantly improved, meanwhile, the hepatic malondialdehyde levels were significantly decreased in all groups fed on phytogenic diets compared to the CTR group (P < 0.05). Furthermore, ORG 0.5 % and MOF 0.5 % groups showed a significant increase in serum total protein, and alternative complement activity (ACH50) (P < 0.05). Attractively, serum lysozyme levels were significantly increased while serum endotoxin values decreased in all groups fed on phytogenic diets. Furthermore, the MOF 0.5 % group showed the highest activities of skin mucus lysozyme, ACH50, and protease (P < 0.05), meanwhile mucosal total immunoglobulins were the highest in ORG 0.5 % and both levels of MOF. ORG 0.5 % and MOF 0.5 % groups showed the highest protection levels of fish following challenge with pathogenic Aeromonas hydrophila. Conclusively, this comparative study showed that both ORG and MOF extract at a 0.5 % level can effectively improve the growth, health, and immune status of Nile tilapia juveniles.

The Efficacy of Geraniol and ß-Citronellol against Freshwater and Marine Monogeneans.

Monogeneans are parasitic flatworms that may be a threat for finfish aquaculture. In this study, the anthelmintic activity of two terpenes, geraniol and β-citronellol, was tested in vitro against ancyrocephalin and diplectanid monogeneans. Experiments were performed in both water and a culture medium. We observed that monogeneans in culture medium may be more tolerant to treatments compared with bioassays performed only in water. Concentrations of 300mg/L of both compounds were required to kill 100% of monogeneans at 1h postexposure. The toxicity of β-citronellol to fish was not evaluated. However, geraniol at 300mg/L and 150mg/L killed juvenile Nile Tilapia Oreochromis niloticus and White Snook Centropomus viridis, respectively, after a few minutes. Therefore, the present work suggests that other alternatives should be studied for use against monogeneans in aquaculture.

Effects of different stocking densities on Nile tilapia performance and profitability of a biofloc system with a minimum water exchange

The determination of an optimum stocking density should be obtained according to a complex assessment, in which growth performance, water quality, animal welfare, and production costs need to be considered. In this context, the objective of this work was to evaluate different stocking densities of Nile tilapias in biofloc technology (BFT) with minimal water renewal. Six hundred masculinized Nile tilapia juveniles with an initial average weight of 133.91 g were evaluated at four different stocking densities (18.75, 37.50, 56.25, and 75.00 fish‧m−3) and four replications, during 260 days of trial. The increase in stocking density resulted in a reduction of DO and pH. The minimum water renewal at a rate of 5%‧day−1 promoted an average reduction of settleable solids in the system of 23.75% at each discharge. The final biomass followed a quadratic regression on the stocking density, with a maximum at 72.27 fish‧m−3 or 36.86 kg‧m−3. However, the greatest daily weight gain (2.84 g‧day−1) that resulted in the highest average final body weight (842.26 g) was obtained at the lowest stocking density. We did not obtain any significant differences in body composition. The biofloc, on the other hand, had lower ash content and higher gross energy in the high stocking densities. Regarding gill morphometry, we found a greater number of branchial lesions in the highest and lowest stocking density evaluated. By an economical assessment, if the sales price is influenced by the final body weight, the reduced average harvest weight in higher stocking densities could lead to low profitability or even financial loss. Therefore, it is concluded that the use of intermediate stocking density, around 33 fish‧m−3, has higher profitability since it produces a large proportion of harvested fish that reach high body weights, and possible high selling prices, combined with desirable biomass.

Apparent digestibility of protein hydrolysates from chicken and swine slaughter residues for Nile tilapia

The objective of the study was to determine the physical-chemical composition of protein hydrolysates from meat by-products from poultry and swine processing, as well as to evaluate the apparent digestibility coefficients (ADC) of crude protein (ADCCB), crude energy (ADCCE), essential (ADCEAA), and non-essential (ADCNEAA) amino acids for juvenile Nile tilapia. The physicochemical composition (dry matter, crude protein, crude energy, essential and non-essential amino acids) of the hydrolyzed swine liver proteins (HSLP), porcine mucosa (HSMP), feathers (HFP) and chicken (HPP) was analyzed. Five diets were formulated, with one reference diet and four tests diets composed of 80% of the reference diet and 20% of hydrolyzed protein (HSLP, HSMP, HFP and HPP). For the apparent digestibility test, 500 juvenile Nile tilapia (69.08 ±0.69 g) were randomly distributed, 25 fish per tank adapted with a fecal collection cup. The animals were fed at a rate of 4% of live weight per day divided into five daily feedings, for a total of 30 days. The indirect method of feces collection was followed using 0.1% chromium oxide III (Cr2O3) as an inert marker. Significant differences were found between the ADCs of the different protein hydrolysates evaluated (p<0.05) for practically all nutritional fractions analyzed, except arginine, tryptophan, cystine and taurine. The mean values of the experimental groups HSLP (87.53 and 79.53%), HFP (89.05 and 83.37%) and HPP (90.84 and 87.29%) referring to ADCCP and ADCCE respectively were lower (p>0.05) to the ADCCP (97.12%) and ADCCE (96.62%) averages obtained for HSMP. In general, the averages of the ADCEAA; ADCNEAA for HSMP (98.59%) were higher than that observed in the HSLP group (90.54%; p<0.05), but not differing from the HFP (95.45%) and HPP (93.85%) groups. It is concluded that the hydrolysates evaluated showed high values of the nutritional fractions of interest for aquaculture, in addition to high apparent digestibility rates for Nile tilapia.

Effects of Artemisia annua alcohol extract on physiological and innate immunity of Nile tilapia (Oreochromis niloticus) to improve health status

Plants are a potential source of active molecules and are environmentally safer and cheaper than synthetic antibiotics. Bioactive compounds of Artemisia annua have shown pharmacological activities and are used globally as a supplement. The present study tested whether dietary supplementation with alcohol extract of the plant A. annua (ae-Aa; patent BR10201902707) improves the health status of juvenile Nile tilapia and increases resistance to diseases when fish are challenged with the bacteria Aeromonas hydrophila. The experimental design was completely randomized with four experimental groups (0.0, 0.1, 0.25, and 0.5% ae-Aa in the diets) with five repetitions (12 fish per repetition/experimental unit). We assessed serum glucose and cortisol levels in plasma, leukocyte respiratory activity, total plasma protein, serum lysozyme levels, as well as the number of circulating red blood cells and fish leukocytes at the end of the 30 days of feeding (phase I) and 24h after exposure to bacteria (phase II). The levels of lipid peroxidation, catalase activity and glutathione S-transferase of fish were also analyzed. The supplementation of 0.5% of ae-Aa was sufficient to increase the respiratory burst of leukocyte and lysozyme activity, total plasma protein, blood thrombocytes, neutrophils and monocytes after bacterial challenge (P < 0.05), and minimized stress response with decreases in plasmatic glucose and cortisol, and reduction in lipid peroxidation levels (P < 0.05). Results of the present study suggest that ae-Aa as a dietary supplement has benefits, including supplementation with 0.5% A. annua extract for 30 days to minimize the stress response and modulate innate immunity in Nile tilapia, providing fish with greater resistance and disease protection.

A short pulse of dietary algae boosts immune response and modulates fatty acid composition in juvenileOreochromis niloticus

Considering algae as novel dietary ingredient for aquafeeds, this study evaluates the effects of three algae, Ulva rigida, Crassiphycus corneus (formerly Hydropuntia cornea) and Scenedesmus almeriensis, on non-specific immune response and fatty acid profile in juvenile Nile tilapia (Oreochromis niloticus) after a short dietary administration period (30 days). U. rigida, C. corneus and S. almeriensis diets (UL-25, CC-25 and SC-25 respectively) included 25% dry algae biomass, whereas an algae-free diet was used as control. Biological samples were taken at 7, 15 and 30 days. Diet SC-25 significantly improved respiratory burst, alternative complement (ACH50) and lysozyme activity (p < .05). Regarding tissue fatty acid composition, SC-25 diet reduced the levels of saturated fatty acid in liver and muscle, while increased levels of C20:3n6 and eicosapentaenoic acid (EPA) in liver, and total n-3 content, arachidonic acid (ARA), EPA and docosahexaenoic acid (DHA) in muscle (p < .05). UL-25 and CC-25 groups showed the lowest levels of ARA in liver but increased levels of monounsaturated fatty acids. In conclusion, the results obtained lead us to consider the use of a short pulse of dietary algae is suited for improving the immune response and modulating the tissue fatty acid composition in this fish species.

Modeling the Effects of Water Temperature on Growth Rates, Gastric Evacuation and the Return of Appetite in Juvenile Nile Tilapia, Oreochromis niloticus L.

Optimized aquafeeds have long been a major concern of the sustainable aquaculture development. Not only should the feed composition meet the nutritional requirements of the fish, it should also be reasonably managed (feed ration and feeding frequency) to enhance the feed utilisation efficiency, growth performance and decrease the amount of wastes. At present there is no detailed information on how rearing temperature impacts gastric evacuation rate, return of appetite (RA) and daily feed ration among tilapias, considered as one of the leading fish species for worldwide aquaculture production. The objective of this study was to develope mathematical models to estimate maximum daily feed intake for Nile tilapia in relation to feeding frequency and water temperature. Growth was measured in 480 fish (initial body mass 4.30&amp;plusmn;0.02 g) fed in slight excess, following their exposure to four thermal treatment (22, 26, 30 and 34 &amp;deg;C) (four replications per treatment, 21-days rearing period, growth monitoring at 5-days intervals). Gastric evacuation and return of appetite measurement were made by radiographic technique. &#x0D; &#x0D; A growth model was developed using a stepwise multiple-regression analysis against fish body mass and water temperature (r2 = 0.939, df = 15) as follow: SGR (%M/day) = -70.606 + 98.433 Log T&amp;deg; &amp;ndash; 33.762 (Log T&amp;deg;)2 - 0.153 Log M (Log T&amp;deg;)2. The gastric emptying was described by an exponential function, which was found to be inversely related to the RA. The instantaneous evacuation rates (Re) determined by linearizing the data were strongly affected by rearing temperature (Q10 = 0.047) in Nile tilapia. The RA following a satiation meal was also significantly dependent on rearing temperature. Based on these data, the maximum daily feed consumption was estimated in relation to feeding schedule for juvenile tilapia reared at different temperatures. &#x0D; &#x0D; Considering that unsuitable use of feed adversely impacts on the farm revenue and profit, these results contribute to improve feed management strategies.

Acute-lethal toxicity test on juvenile Oreochromis niloticus exposed to Piper betle extract under static exposure

Purpose This study aims to evaluate the effect of Piper betle leaf extract towards the acute-lethal toxicity, LC50 of red Nile tilapia juveniles (Oreochromis niloticus). Design/methodology/approach Ten red Nile tilapia juveniles per tank (in triplicate) were used as an experimental fish for the LC50 bioassay. Five different concentrations of P. betle extract; 80 ppm, 90 ppm, 100 ppm, 110 ppm and 120 ppm, were tested on the red Nile tilapia juveniles and one tank was acting as a control. The progress of the LC50 and lethal time of fish mortality were observed and recorded within the random interval of 96 h. The value for LC50 was determined as 100 ppm of P. betle leaf extract. Higher number of fish mortalities was observed when concentration higher than 100 ppm was tested on to the red Nile tilapia juveniles. Findings Data obtained shows that the P. betle concentration of 120 ppm accelerated the fish mortality period. Originality/value However, adaption of P. betle extract occurred after 50 h, as there was no fish mortality observed within the time.

Compensatory growth in Nile tilapia Oreochromis niloticus: feed conversion ratio, size heterogeneity, and proximal composition

A feeding test was performed to evaluate compensatory growth in the Nile tilapia (Oreochromis niloticus) and to assess changes in feed conversion ratio (FCR), body condition, and carcass composition associated with the imposed feeding strategy. The experiment was carried out under two different stages, restricted (RS) and compensated (CS), with six weeks long each other. Three hundred juveniles of Nile tilapia (average weight of 16.4 ± 0.2 g) were divided into three treatments and one control. The control group was fed to apparent satiation four times a day in both stages. The RS treatments were based on 100% (RS100), 80% (RS80), and 60% (RS60) of a feeding chart, respectively. In the next six weeks, fishes from the CS treatments (CS100, CS80, and CS60) were then fed to apparent satiation four times a day. In the RS, the control group displayed the most considerable weight gained, but with a significant FCR. Nevertheless, in the CS, the previous restricted treatments (RC80 and RC100) showed a compensatory growth, with a smaller FCR than the control group. The restricted-compensated rations did not have a significant effect on the size heterogeneity; when the food is restricted, fish use to moisturize their tissue to compensate for the muscle loss until they receive more food. However, when the food restriction levels are too high, the weight gain, lipid, and protein levels do not recover as they were before. Thus, restricted (marginally) and compensatory feeding strategies provide evidence that growth rates of fishes can be regulated.

Effects of different levels of vitamin B6 in tank water on the Nile tilapia (Oreochromis niloticus): growth performance, blood biochemical parameters, intestine and liver histology, and intestinal enzyme activity.

According to the importance of vitamin B6 (pyridoxine) as a water-soluble vitamin on the physiological conditions of aquatic animals, the present study aimed to investigate effects of different concentrations of this vitamin in recycle system culture water on the Nile tilapia (Oreochromis niloticus). Treatments including 0 (control), 10, 20, 30, and 40mgL-1 vitamin B6 were adjusted in triplicate recirculating systems. Each of the experimental tanks (100L) was stocked 15 fingerling Nile tilapia during 60-day experimental period. According to the findings, weight gain in treatments of 30 and 40mgL-1 pyridoxine was significantly higher than the other treatments while blood cortisol hormone in the treatment of 40mgL-1 was significantly highest among the treatments. In addition, mid-intestine trypsin activity in the treatment of 40mgL-1 was significantly higher than the other treatments. The histological analysis of the intestine showed that the number of mucus-secreting cells significantly decreased in treatments of 30 and 40mgL-1. Our findings here suggest that pyridoxine can possibly be absorbed by the Nile tilapia's body through culture water and it seems 20-30mgL-1 pyridoxine in the culture water is the optimal concentration for the Nile tilapia juveniles in recycle system culture.