Dietary bee pollen affects hepatic–intestinal histomorphometry of Nile tilapia fingerlings

The bee pollen is considered an excellent source of flavonoids, carotenoids, phenolic compounds, sterols and minerals; and possesses the ability to boost the immune system, antioxidant action and other interesting therapeutic effects. This study was carried out aiming to evaluate the inclusion of bee pollen in extruded commercial diets of Nile tilapia fingerlings and its effects on the hepatic‐intestinal histomorphometry and zootechnical performance. A total of 225 tilapia fingerlings (1.25 ± 0.05 g) were distributed in a completely randomized design in 15 tanks (30 L) maintained in a recirculation water system with three treatments (0% or control, 1.5% and 2.5% of bee pollen inclusion) and five replicates. Feeding rates were defined from the weekly biometrics and periodic monitoring of the physical–chemical water quality parameters. The water quality variables remained within the appropriate range for the species throughout the experiment. There was no significant difference for the somatic indexes and zootechnical parameters in this experiment. However, the inclusion of bee pollen in Nile tilapia fingerlings diets showed a linear increase in hepatocyte morphology (p = .0098). For the intestinal variables of villus height a significant linear increase was observed (p < .05) as the pollen inclusion increased. In fish that received 2.5%, the number of goblet cells was significantly higher (p < .001) than control group and 1.5%. In this sense, the inclusion up to 2.5% bee pollen in extruded commercial diets of Nile tilapia fingerlings had a positive impact on hepato‐intestinal histomorphometry without causing negative effects on the zootechnical performance.     

Total and available tryptophan requirement of Nile tilapia,Oreochromis niloticus,fingerlings

The dietary total and available requirement of tryptophan of Nile tilapia fingerlings was determined using linear regression analysis. Six hundred fish (3.4 ± 0.0 g) were fed diets containing 296.4 g/kg of crude protein and 14.1 MJ/kg of digestible energy. Five extruded diets containing 2.5, 3.0, 3.4, 3.8 and 4.2 g/kg of total tryptophan were evaluated. Fish were fed four times a day during 45 days. Final body weight, weight gain, feed intake, feed conversion ratio and net protein utilization of fish fed Trp 3.4 and Trp 3.8 diets were improved compared to fish fed Trp 2.5 and Trp 4.2 diets. No significant differences in survival rate, whole‐body moisture and ash were observed. Whole‐body amino acid profile of fish fed different diets did not differ statistically (p > .05). Fish fed Trp 3.0 and Trp 3.4 diets showed higher tryptophan retention compared to fish fed Trp 2.5 and Trp 4.2 diets. Excepting blood glucose, no effects of dietary tryptophan on haematological parameters were observed. The dietary total tryptophan requirement of Nile tilapia fingerlings based on weight gain was estimated to be 3.4 g/kg (11.0 g/kg of dietary crude protein) or 3.0 g/kg of available tryptophan (11.0 g/kg of dietary digestible protein).     

Dietary lipid sources affect the performance of Nile tilapia at optimal and cold,suboptimal temperatures

Five sources of dietary fatty acids (fish, linseed, sunflower, olive and coconut oils) were evaluated in juvenile Nile tilapia in two trials: at optimal (28°C) and suboptimal (22°C) temperatures lasting 9 and 12 weeks, respectively. At 28°C, there was no clear effect of dietary source on fish growth, but at 22°C, the highest daily weight gain occurred in fish fed sunflower, linseed and fish oil. Feed efficiency and apparent net protein utilization increased as the amount of unsaturated fatty acids, especially n‐3 polyunsaturated fatty acids (PUFA), in the diet increased. Coconut oil, which is rich in saturated fatty acids (SFA), led to the worst growth results, especially at 22°C, with the lowest weight gain, feed intake and feed utilization by tilapia. The body fatty acid profile, in % of total fatty acids, was dependent on diet composition. However, for all treatments, PUFA body content increased with the decrease in temperature, but SFA and monounsaturated fatty acids remained the primary contributors to the body profile. Either fish oil or vegetable oil may be used as sources of dietary fatty acids for Nile tilapia, but at suboptimal temperatures, a dietary source containing more PUFA and less SFA improves performance.     

Dietary astaxanthin modulated the performance,gastrointestinal histology,and antioxidant and immune responses and enhanced the resistance of Litopenaeus vannamei against Vibrio harveyi infection

Aquaculture International - Astaxanthin (AX) is one of the commonly used feed supplements to enhance the growth performance and provide antioxidant and immune functions of several aquatic animals....     

Moderate salinities enhance growth performance of Nile tilapia (Oreochromis niloticus) fingerlings in the biofloc system

The biofloc technology (BFT) has recently gained attention as an economic and environmentally sustainable system for aquaculture. The use of BFT with salinized water could be used to minimize the negative effects of nitrogenous waste and improve the growth performance of Nile tilapia. This work evaluated the growth performance, survival, gill lesions, and fillet composition of tilapia fingerlings (Oreochromis niloticus) reared during 70 days with different salinities (0, 4, 8, 12, and 16 g/L) in a biofloc previously developed. The results indicated that the use of mature bioflocs alone was sufficient to avoid fingerling mortality due to nitrite peaks. Moreover, the salinized water, especially between 4 and 8 g/L (maximum points around 6 g/L), can be recommended in BFT to improve the growth performance of tilapia in the initial culture phase. The salinity level that was evaluated did not affect fillet composition nor the occurrence of gill lesions. The total ammonia nitrogen concentration was lower in freshwater than in salinized water (p < 0.05). Nitrite peaks in salinities of 12 and 16 g/L appeared later and were higher in comparison to other treatments. Considering minimal water exchange in BFT, the use of salinized water in this system may be environmentally viable.     

Dietary Aspilia mossambicensis and Azadirachta indica supplementation alter gonadal characteristics and histology of juvenile Nile tilapia (Oreochromis niloticus)

The use of medicinal plants to control reproduction in aquaculture have recently received considerable attention because they are biodegradable, safe, effective and locally available. However, information on their effects on gonadal characteristics and histological features in fish is currently limited. The present study evaluated the gonadal characteristics and histological changes of Nile tilapia, Oreochromis niloticus gonads fed on Aspilia plant, Aspilia mossambicensis and Neem tree, Azadirachta indica. Juvenile fish were fed diets supplemented with four doses (1.0, 2.0, 4.0 and 8.0 g/kg diet) of A. mossambicensis or A. indica leaf powders at 3% of their body weight daily for 90 days to examine absolute fecundity (AF), relative fecundity, gonadosomatic index (GSI) and histology of gonads. The antifertility phytocompounds in the two plants were quantified by using standard methods. Results indicated that, all doses of A. indica and A. mossambicensis used reduced significantly AF and GSI values (p < 0.05). Dose‐dependent histological alterations of gonads were noticed in both plants starting from doses of 2.0 g/kg in males and 4.0 g/kg in females. The highest percentages of total flavonoids (23.7%) and alkaloids (14.2%) were obtained from A. indica ethanol extract (p < 0.05). Taken together, dietary supplementation with A. mossambicensis and A. indica leaf powders alter gonadal characteristics of O. niloticus and histology triggered by alkaloids and flavonoids. Farmers interested in using the two plants to control prolific breeding should limit the dose inclusion to 2 g/kg to avoid severe effects on fish testis and ovaries.     

Growth performance and feed utilization of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) and tilapia galilae Sarotherodon galilaeus (Linnaeus, 1758) fingerlings fed plant protein-based diets

This study was designed to determine the effect of complete substitution of fish meal (FM) by three plant protein sources including extruded soybean meal (SBM), extruded full‐fat soybean (FFSB) and corn gluten meal (CGM) on growth and feed utilization of Nile tilapia Oreochromis niloticus and tilapia galilae Sarothrodon galilaeus. Four isonitrogenous of crude protein (ca. 28.0%) and isocaloric (ca. 19 MJ kg⁻¹) experimental diets were formulated. The control diet (diet 1) was prepared with FM as the main protein sources. Diets 2–4, each FM control diet, were completely substituted with SBM (diet 2), FFSB (diet 3) and CGM (diet 4). l ‐lysine and dl ‐methionine were added to plant protein diets to cover the nutritional requirements of tilapia. Each treatment was allocated to three net pens and fed for 17 weeks. Nile tilapia fed the control diet showed significantly higher (P≤0.05) values for final body weight (FBW), feed intake (FI), weight gain (WG) and specific growth rate (SGR), whereas fish fed the diet with CGM achieved the lowest values. Tilapia galilae fed SBM diet recorded the highest (P≤0.05) values for growth performance. Better feed conversion ratio (FCR) for both Oreochromis niloticus and Sarothrodon galilaeus was observed when fish were fed SBM diet, whereas the worse FCR was recorded for FFSB diet. Feed utilization parameters including protein productive value (PPV), fat retention (FR) and energy retention (ER) showed significant differences (P≤0.05) for both the species fed different dietary protein sources. The present results suggest that, for Nile tilapia, both SBM and FFSB supplemented with dl ‐methionine and l ‐lysine can completely replace dietary FM. Meanwhile, S. galilaeus fed SBM diet exhibited comparable growth and feed utilization with those fish fed a fish‐meal‐based diet.     

Effect of experimental arginine supplementation on the growth,immunity and resistance of tilapia fingerlings to Streptococcus agalactiae

Streptococcosis causes serious economic losses to fish farms every year. A four‐week feeding trial was carried out to evaluate arginine (ARG) supplementation in the diet of Nile tilapia (Oreochromis niloticus) fingerlings challenged by Streptococcus agalactiae. Fish were fed with experimental diets containing five levels of supplementation with 1.39%, 1.76%, 1.97%, 2.18% or 2.39% analysed level of ARG. Each diet was randomly distributed in 30 tanks containing 20 fish/tank. After 30 days, no differences were observed in performance parameters, weight gain, daily weight gain, specific growth rate, feed intake or food conversion. After the performance assay, fingerlings were infected with 1.95 × 10⁸ CFU/fish of Streptococcus agalactiae. Mortality was verified daily, and the respiratory burst of leucocytes and nitric oxide production were measured at 0 hr, 24 hr, 7 days and 15 days after infection. The survival rate of the fish is compared using the Kaplan–Meier method, with values of 4.29%, 14.8%, 10.8%, 17.2% and 33.3% for the 1.39, 1.76, 1.97, 2.18 and 2.39 treatments respectively. A reduction in the mortality rate and a boost in the immune responses was observed in all the supplementations of ARG in the diet; however, the best survival rates were obtained in the treatments with 2.39% ARG as well as the most efficient immune responses.     

Effects of dietary inulin and Jerusalem artichoke (Helianthus tuberosus) on intestinal microbiota community and morphology of Nile tilapia (Oreochromis niloticus) fingerlings

This study investigated the effects of dietary inulin and Jerusalem artichoke (JA) on intestinal microbiota and morphometry of Nile tilapia fingerlings. Five treatment diets were designed to supplement inulin at 0 (basal diet), 2.5 and 5.0 g/kg, and JA at 5.0 and 10.0 g/kg. Nile tilapia larvae were fed experimental diets from the first feeding through the fingerling stage (84 days). The cultivation‐dependent technique showed that dietary inulin at 5.0 g/kg and JA (at both levels) increased lactic acid bacteria and Bifidobacterium spp., but decreased Vibrio spp. (p < .05). PCR‐DGGE targeting 16S ribosomal RNA gene revealed that dietary inulin and JA generated different profiles of microbial community compared with fish fed a basal diet. Compared with fish fed the basal diet, a greater intestinal villi height was observed in fish fed 5.0 g/kg inulin and JA at both levels (p < .05). A larger relative goblet cell number were observed in the anterior intestine of fish fed 5.0 g/kg inulin or JA (p < .05). Overall, dietary inulin (5.0 g/kg) and JA (5 and 10.0 g/kg) since the first feeding had effects on modulating the intestinal microbiota and morphology of Nile tilapia fingerlings.     

吉富罗非鱼对饲料中苯丙氨酸的需要量

分别用含6种水平(质量比分别为0.78%、0.95%、1.09%、1.34%、1.51%和1.72%)苯丙氨酸(phenylalanine,Phe)的等氮等能(粗蛋白30.10%,总能17.73 MJ/kg)饲料,在池塘网箱中(实验期间水温为24~32℃)饲喂初始体重为(52.70±1.80)g的吉富罗非鱼60 d,考察饲料Phe对吉富罗非鱼(GIFT,Oreochromis niloticus)生长性能、饲料系数、体成分、部分血清生化指标及前肠消化酶活性的影响,以期获得吉富罗非鱼对饲料苯丙氨酸的需要量。结果表明,随着饲料中Phe水平的升高,吉富罗非鱼的增重率、特定生长率、蛋白质效率、蛋白质沉积率、肥满度、肝体比和脏体比均呈现先上升后下降的趋势,饲料系数呈现先下降后上升的趋势;全鱼粗脂肪和全鱼灰分含量显著上升(P0.05),肌肉灰分含量显著下降(P0.05)。饲料中Phe对全鱼水分和粗蛋白质、肌肉水分、肌肉粗蛋白质和肌肉粗脂肪含量无显著性影响(P0.05);各实验组的肌肉氨基酸含量差异不显著(P0.05)。饲料中Phe显著影响血清中谷丙转氨酶活性,甘油三酯、总胆固醇和葡萄糖的含量(P0.05),对谷草转氨酶活性无显著性影响(P0.05);Phe显著影响肠蛋白酶、肠脂肪酶和肠Na~+-K~+-ATP酶活性(P0.05),而对肠淀粉酶活性影响不显著(P0.05)。以增重率、饲料系数和蛋白质效率为评价指标,通过二次回归分析可知,吉富罗非鱼对饲料中Phe需要量为1.17%~1.21%,占饲料蛋白质的3.89%~4.02%。本研究结果为合理配制吉富罗非鱼配合饲料提供了理论依据。     

Effects of zinc oxide supported on zeolite on growth performance,intestinal barrier function and digestive enzyme activities of Nile tilapia

A total of 720 Nile tilapia fingerlings were allocated to four treatments and used to investigate the effects of zinc oxide supported on zeolite (Z‐ZnO) on growth performance and intestinal function. The basal diet (control) was not supplemented with zinc and contained 60 mg Zn kg^?1. The other three groups were added 30 mg Zn kg^?1 to the basal diet, in which zinc was supplemented as Z‐ZnO, Z + ZnO (mixture of zeolite and ZnO) or ZnSO₄, respectively. As compared to the control, supplemental Z‐ZnO improved (P < 0.05) specific growth rate, protein efficiency ratio (PER) and survivor ratio; increased (P < 0.05) villus‐height‐to‐crypt‐depth ratio and transepithelial electrical resistance; decreased (P < 0.05) mucosal‐to‐serosal flux of dextran 4 kDa; and improved (P < 0.05) intestinal activities of protease, amylase, lipase and alkaline phosphatase. Fish fed with Z‐ZnO had higher (P < 0.05) specific growth rate and PER, and better intestinal barrier function than those fed with ZnSO₄ or Z + ZnO. The zinc concentrations in whole body and vertebrae were not affected by dietary treatments. The results indicated that Z‐ZnO improved intestinal morphology, barrier function and digestive enzyme activities. Such changes in intestinal health in the presence of Z‐ZnO might contribute to its improvement in growth performance.     

Effect of ginger and its nanoparticles on growth performance,cognition capability,immunity and prevention of motile Aeromonas septicaemia in Cyprinus carpio fingerlings

Novel study was performed to evaluate the efficacy of ginger (GN) and its nanoparticles (GNNP) on growth, cognition, immunity and prevention of motile Aeromonas septicaemia (MAS) in Cyprinus carpio fingerlings. Fish were divided into five groups fed diet 1 (control; no additives), diet 2 (0.5 g of GN), 3 (1 g of GN), 4 (0.5 g of GNNP) and 5 (1 g of GNNP) per kg feed for 30 days. In the behavioural test, fish were individually placed in a foraging maze to evaluate their cognition capability and feeding behaviour. At the end of feeding period, fish fed GN and GNNP showed significant better final weight than the controls. GN and GNNP significantly increased total protein, globulin and lysozyme, whereas 1 g GNNP group was the highest. One gram of GN, 0.5 g and 1 g GNNP enhanced cognition capability, while GN and GNNP increased percentage of fish fed in the maze. Brain acetylcholinesterase was significantly decreased than control in 1 g GN group. GNNP succeeded in the prevention of MAS more than GN, because no mortalities and 100% relative percentage survival (RPS) were detected in 1 and 0.5 g GNNP and 1 g GN per kg feed, while fish fed 0.5 g GN showed 20% mortalities and 71.4 RPS.     

Effects of dietary orange peel on growth performance,antioxidant activity,intestinal microbiota and liver histology of Gilthead sea bream (Sparus aurata) larvae

This study investigated the effects of dietary orange peel (OP) on growth performance, feed utilization, antioxidant activity, intestinal microbiota and liver histology of Gilthead sea bream (Sparus aurata) larvae (0.32 ± 0.01 g/fish) (mean ± SD). Fish fed iso‐nitrogenous (480 g/kg protein) and iso‐energetic (23 MJ/kg) diets supplemented with OP at concentrations of 0, 1, 3 or 5 g/kg diet, for 60 days. Growth performance and feed utilization parameters were significantly improved by the elevation of dietary OP level, and the optimum level was 5 g/kg diet. The maximum activity of the total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase, alkaline phosphatase enzyme and malondialdehyde in the liver was found at 5.5, 4.6, 3.4, 2.9, 3.7 and 3.8 g OP/kg diet, respectively. All tested bacteria (Staphylococcus spp., Vibrio spp. and Salmonela spp) and total bacterial count decreased significantly in the gut of fish fed high levels of OP (3.0 or 5.0 g/kg). No differences were found in the liver histo‐architecture among treatments after 60 days feeding on OP diets. In summary, dietary OP improved growth rate, antioxidant activity and intestinal microbiota of S. aurata larvae with an optimum range from 2.9 to 5.5 g/kg diet.     

Effect of soybean meal diets on the growth performance,ammonia excretion rates,gut histology and feed cost of Nile tilapia (Oreochromis niloticus) fry

Aquaculture development in Ghana is currently limited by inadequate supply of fingerlings and prohibitive cost of commercial feeds among other challenges. This study tested the feasibility of using low‐cost feeds containing soybean meal instead of fishmeal for nursing Nile tilapia (Oreochromis niloticus) fry. Three isonitrogenous (~48% crude protein) and isoenergetic (~17 kJ/g) diets with increasing inclusions of soybean meal as partial replacements for fishmeal were formulated. A commercial fishmeal‐based fry feed served as the control diet. Triplicate groups of 225 fish per tank (average initial weight: 2.09 ± 0.14 g) were stocked in a recirculating aquaculture system and fed the experimental diets for 21 days. Afterwards, we investigated the postprandial metabolism, nutrient digestibility, growth and gut histology in Nile tilapia fry. Simple economic analyses were also conducted to assess the cost‐effectiveness of the diets used in the feed trial. The dietary inclusions of the soybean meal significantly reduced feed cost by ~43% relative to the control diet. The growth performance and feed utilization parameters did not vary significantly among the different treatments. The soybean diets elicited significant reductions in villi heights and goblet cell numbers, which corresponded with increasing dietary levels of soybean meal. This study confirms the potential of soybean meal as a partial replacement for fishmeal in Nile tilapia fry diets in terms of lower feed costs, fish growth performance, nutrient digestibility and postprandial nitrogenous excretions. The inclusion of soybean, however, affected negatively the gut integrity of the fry.     

The effect of photoperiod on the reproductive performance of the Nile tilapia, Oreochromis niloticus

The reproductive performance of O. niloticus was evaluated in four different photoperiods. Results suggested that long days were the most suitable for egg production and reduction of inter-spawning interval.     

Effects of Cu-exchanged montmorillonite on growth performance, microbial ecology and intestinal morphology of Nile tilapia (Oreochromis niloticus)

A total of 360 Nile tilapia at an average initial body weight of 3.9 g were randomly allocated to 4 treatments, each of which had three replicates of 30 fish/tank and used to investigate the effects of Cu²⁺-exchanged montmorillonite (Cu-MMT) on growth performance, microbial ecology of the skin, gill and intestine, and intestinal morphology. The dietary treatments were: 1) basal diet, 2) basal diet + 1.5 g/kg MMT, 3) basal diet + 30 mg/kg copper as CuSO₄ (equivalent to the copper in the Cu-MMT treatment group), or 4) basal diet + 1.5 g/kg Cu-MMT. The results showed that supplementation with Cu-MMT significantly improved growth performance as compared to control and fish fed with Cu-MMT had higher growth performance than those fed with MMT or CuSO₄. Supplementation with Cu-MMT reduced (P < 0.05) the total intestinal aerobic bacterial counts and affected the composition of intestinal microflora with a tendency of Aeromonas, Vibrio, Pseudomonas, Flavobacterium, Acinetobacter, Alcaligence, Enterobacteriaceae decreasing as compared with control. Measurements of villus and microvillus heights at different sites of the intestinal mucosa indicated that dietary addition of MMT or Cu-MMT improved intestinal mucosal morphology. However, the microbial ecology of the skin and gill was not affected by the addition of CuSO₄, MMT or Cu-MMT. Supplementation with CuSO₄ had no (P > 0.05) effect on the growth performance, microbial ecology and intestinal morphology. The results showed that Cu-MMT exhibited antibacterial activity in vivo and protected intestinal mucosa from invasion of pathogenic bacterium and toxins, resulting in a positive effect on the growth performance.     

Effect of dietary conjugated linoleic acid levels on growth performance,muscle fatty acid profile,hepatic intermediary metabolism and antioxidant responses in genetically improved farmed Tilapia strain of Nile tilapia Oreochromis niloticus

An 8‐week feeding trial was conducted to determine the effect of dietary conjugated linoleic acid (CLA) on growth performance, muscle fatty acid profile, hepatic intermediary metabolism and antioxidant responses in genetically improved farmed Tilapia (GIFT) strain of Oreochromis niloticus (initial body weight: 42.6 ± 0.4 g, mean ± standard deviation). Three replicated groups of GIFT strain of Nile tilapia were hand‐fed to satiation, twice a day, with the diets in which CLA oil, containing mainly the bioactive cis‐9, trans‐11 and trans‐10, cis‐12 isomers, was included at 0 (control), 0.5%, 1%, 1.5%, 2% and 2.5%, respectively, at the expense of fish oil to maintain the constant lipid and energy levels. Growth performance and feed utilization showed no significant differences among the treatments (P > 0.05). The dietary inclusion of CLA modified total percentages of the main groups of fatty acids. Increasing saturated fatty acid content and reduced mono‐unsaturated fatty acid contents in muscle were observed with increasing dietary CLA inclusion (P < 0.05). Total n‐3 fatty acids and total polyunsaturated fatty acids tended to decline with increasing dietary CLA levels (P < 0.05), but n‐6 fatty acids showed no significant differences among the treatments (P > 0.05). Dietary CLA supplementation resulted in the significant increase in the trans‐10, cis‐12 and cis‐9, trans‐11 CLA isomers in muscle (P < 0.05) and also significantly influenced several hepatic enzymatic activities, such as succinate dehydrogenase, lactate dehydrogenase, malic dehydrogenase, lipoprotein lipase and hepatic lipase activities (P < 0.05). Reduced superoxide dismutase and glutathione peroxidase activities, and the decline in malondialdehyde levels were observed in fish fed the CLA‐supplemented diets (P < 0.05), indicating that dietary CLA supplementation showed a powerful antioxidant effect for this fish species. Our study was the first report involved in the effect of dietary CLA inclusion on hepatic intermediary metabolism and antioxidant responses in fish, which could be used as indicators of nutritional and physiological status of the fish species.