Effect of replacing dietary fish oil with soybean oil on growth performance,fatty acid composition and haematological parameters of juvenile meagre,Argyrosomus regius

A nutrition trial with meagre, Argyrosomus regius was assessed to determine the effect of dietary replacement of fish oil (FO) by soybean oil (SO) on the growth, feed utilization, body composition, fatty acid composition and basic haematological parameters. Six isonitrogenous (47% crude protein) and isoenergetic (gross energy 22 kJ/g) experimental diets were formulated by replacing 0 (FO), 20 (S20), 40 (S40), 60 (S60), 80 (S80) and 100 (S100) % of the FO with SO. Fish were fed three times daily to near satiation for 14 weeks. The specific growth rate (SGR) of fish fed S100 diet was significantly lower than the other treatments, except SO80 diet. The fish fed SO100 diet displayed significantly higher feed conversion ratio than that of other diets (P < 0.05). It was observed that fish fed the SO100 and SO80 diets displayed haemoglobin (HGB) levels significantly lower (P < 0.05) than fish fed the SO20 diet. Packed cell volume (PCV) of fish fed SO20 diet was significantly higher compared to SO100. The white blood cell (WBC) and red blood cell (RBC) remained unaffected by dietary treatment. The docosahexaenoic acid (22:6n‐3, DHA) and eicosapentaenoic acid (20:5n‐3, EPA) levels of meagre were significantly reduced by the substituting of dietary SO by FO at the end of the feeding period. The level of linoleic acid (18:2n‐6, LA) and linolenic acid (18:3n‐3, LNA) significantly raised in fish fed with SO diets (P < 0.05). The results of this study showed that SO could be replaced FO up to 80% in meagre diet without negative effect on growth performance and basic haematological parameters. Furthermore, the maximum level of FO replacement with SO determined by second order polynomial regression analysis, was 30.1% on the basis of maximum SGR.     

Influence of digestible protein levels on growth and feed utilization of juvenile meagre Argyrosomus regius

This study investigates the effect of digestible protein levels in experimental diets for meagre (Argyrosomus regius). A group of 253 fish, 52 g of mean weight, was distributed in 12 tanks, three replicates per treatment. Four isolipidic diets (170 g kg^?1 crude lipid) with different digestible protein levels (350 g kg^?1, 430 g kg^?1, 490 g kg^?1 and 530 g kg^?1) were formulated using commercial ingredients. The trial lasted 62 days. Meagre fed diets 430, 490 and 530 g kg^?1 obtained higher TGC (2.47, 2.57, 2.69 × 10^?3, respectively) than fish fed diet 350 g kg^?1 (2.14 × 10^?3). Group of fish fed diet with 350 g kg^?1 DP showed the lowest ammonia excretion level. According to the in vitro digestibility trial diets with 350 and 430 g kg^?1 DP released less amino acids in comparison with diet with 49% DP, although in vivo digestibility test did not show significant differences among diets 430, 490 and 530 g kg^?1 DP. Using the quadratic regression, optimal digestible protein intake according to the ECR for rearing juvenile meagre was recorded in 0.8 g DP/100 g fish and day.     

First approach to studying the genetics of the meagre (Argyrosomus regius; Asso, 1801) using three multigene families

The meagre (Argyrosomus regius) is a commercially important species for fisheries, and aquaculture production has been increasing in recent years. However, this growing importance has not been matched by increased genetic knowledge of the species. For this reason, an initial approach has been made to understanding the genetics of the meagre, using three particular multigene families (45S and 5S ribosomal DNA and U2 snRNA gene) as both molecular and cytogenetic markers. Only one type of 5S rDNA and only one ITS‐1 (from 45S rDNA) were obtained, and these therefore could provide the basis for the development of genetic markers for this species. However, the U2 snRNA gene produced a multi‐band electrophoretic pattern, and some of these bands were demonstrated to be linked with the U1 snRNA gene. This linkage could also provide a good species‐specific marker which could be useful for tracing the evolutionary history of the Sciaenidae family. In this study, we have described for the first time the karyotype of the meagre: this is composed of 48 acrocentric chromosomes. Each of the three gene families were localized on different chromosome pairs, although the U2 snRNA gene probe was also located scattered throughout the genome of the meagre, as expected by the amplification pattern.     

Evaluation of dietary histidine supplementation on meagre,Argyrosomus regius,juvenile growth,haematological profile,stress and muscle cellularity

Histidine plays an important role in haemoglobin synthesis, antioxidant defence system and stress resistance, and it is thought to be a limiting amino acid in most meagre diets. In this study, two different diets, a control and a diet supplemented with 3% histidine, were tested in 60‐day‐old meagre (initial weight—6.2 g) for 82 days. Survival varied between 92% and 94%, and neither SGR nor whole fish composition seemed to be affected by the diet. When fish were submitted to a stress test (outside water for 30 s), it was observed that the levels of glucose and lactate significantly increased in both treatments. The concentration of cortisol increased after the stress test only in the His 30 g/kg group. Muscle cellularity was affected by the diets, where the control group showed a higher mean fibre area and lower fibre density. These results, associated with a lower frequency of smaller fibres, suggest a decrease in fibre recruitment and a higher fibre hypertrophy. In conclusion, the supplementation of diets with 3% led to a more pronounced response to the stress test in terms of cortisol levels and increased muscle fibre recruitment, decreasing muscle fibre hypertrophy contribution to muscle growth.     

Dietary amino acid profile affects muscle cellularity,growth, survival and ammonia excretion of meagre (Argyrosomus regius) larvae

Formulation of diets according to fish amino acid (AA) qualitative requirements may improve fish growth. Two diets with different AA profiles were tested on 16‐day‐old meagre during 20 days. The first diet had an AA profile closer to meagre larval AA requirements (BAL), whereas the second had a different AA profile (UNBAL). Results showed that larvae fed the diet with higher similarities to the AA profile of meagre carcass had a higher final weight (19.8 ± 0.5 mg versus 13.4 ± 1.8 mg) and lower ammonia excretion after being fed (0.6 ± 0.1 ml/(g DW. larvae. h) and 0.8 ± 0.1 ml/(g DW larvae. h)). A higher mean fibre area was obtained in 36 DAH larvae fed the BAL diet (224.8 ± 33.3 μm² versus 158.8 ± 34.5 μm²) as well as higher larval weight. When fibre area distribution was analysed, a higher frequency of larger fibres was observed in 36 DAH BAL larvae, suggesting that fibre hypertrophy had a higher importance in this treatment. In conclusion, this study shows that meagre larvae fed a diet with an AA profile closer to their requirements had lower nitrogen losses and higher final weight, as result of higher muscle hypertrophy.     

The importance of dietary HUFA for meagre larvae (Argyrosomus regius; Asso, 1801) and its relation with antioxidant vitamins E and C

Despite the interest of meagre (Argyrosomus regius) as a fast‐growing candidate for Mediterranean aquaculture diversification, there is a lack of information on nutrition along larval development. Importance of highly unsaturated fatty acids (HUFA) and the antioxidant vitamins E and vitamin C has not been investigated yet in this species. Six diets with two levels of HUFA (0.4% and 3% dw), two of vitamin E (1500 and 3000 mg kg^?1) and two of vitamin C (1800 and 3600 mg kg^?1) were fed to 15 dah meagre larvae. Larval growth in total length and dry body weight was significantly lowest in larvae fed diet 0.4/150/180 and showed few lipid droplets in enterocytes and hepatocytes and lower HUFA contents than the initial larvae. Increase in dietary HUFA up to 3%, significantly improved larval growth and lipid absorption and deposition. Besides, among fish fed 3% HUFA, increase in vitamin E and vitamin C significantly improved body weight, as well as total lipid, 22:6n‐3 and n‐3 fatty acids contents in the larvae. Thus, the results showed that 0.4% dietary HUFA is not enough to cover the essential fatty acid requirements of larval meagre and a high HUFA requirement in weaning diets is foreseen for this species. Besides, the results also pointed out the importance of dietary vitamin E and C to protect these essential fatty acids from oxidation, increase their contents in the larvae and promote growth, suggesting high vitamin E and C requirements in meagre larvae (higher than 1500 and 1800 mg kg^?1 for vitamin E and vitamin C respectively).     

Effect of increased dietary protein level in meagre (Argyrosomus regius) juvenile growth and muscle cellularity

In this study, two different dietary protein levels were tested (500 and 600 g/kg) in meagre juveniles of approximately 2 g, to determine whether a higher body protein diet would favour muscle growth. Results showed that meagre survival and growth were not affected by different levels of dietary protein. However, a higher content of protein was observed in the body composition of meagre fed the P60 diet (656 g/kg versus 624 g/kg). When fish were 82 days after hatched (DAH), protein retention efficiency was significantly higher in fish that were fed the P50 diet (37.1% versus 32.5%). Muscle cellularity changed considerably from the beginning to the end of the trial. The contribution of fibre hyperplasia to muscle growth was reduced although still accounted for 30% in 96 DAH meagre. Several differences were found in the frequency of fibres with areas between 1,000 μm² and 2,200 μm² between younger and older meagre, but no effect was found associated with dietary protein. This study suggests that neither growth nor muscle cellularity of fast‐growing juvenile meagre is positively affected by an increased dietary protein levels.     

Acute toxicity of ammonia in Meagre (Argyrosomus regius Asso, 1801) at different temperatures

Argyrosomus regius (3.0 ± 0.9 g) were exposed to different concentrations of ammonia in a series of acute toxicity tests by the static renewal method at three temperature levels (18, 22 and 26°C) at a pH of 8.2. Low temperature clearly increased the tolerance of the fish to total ammonia nitrogen (TAN) and unionized ammonia (NH₃) (P < 0.05). While the 96‐h LC₅₀ values of TAN were 19.79, 10.39 and 5.06 mg L^?1, the 96‐h LC₅₀ of NH₃ were 1.00, 0.70 and 0.44 mg L^?1 at 18, 22 and 26°C respectively. The safe levels of NH₃ for A. regius was estimated to be 0.10, 0.07 and 0.04 mg L^?1 at 18, 22 and 26°C respectively (P < 0.05). This study clearly indicates that A. regius is more sensitive to ammonia than other marine fish species cultured on the Mediterranean and Eastern Atlantic coasts.     

Effects of salinity level on the survival,growth, feed utilization,carcass composition,haematological and serum biochemical changes of juvenile Meagre (Argyrosomus regius) (Asso, 1801) grown in ground saltwater

A study was performed to examine the effects of salinity on water quality, fish performance, carcass composition and haemato‐biochemical parameters in juvenile meagre, Argyrosomus regius. Fish (5.0 g) were stocked in fibreglass tanks at four salinity levels: 8‰, 16‰, 24‰ and 32‰, and fed a pelleted diet (47/17 protein/lipid) for 56 days. Results indicated that the growth, feed utilization, carcass composition and haemato‐biochemical parameters of meagre gradually improved with the increase in salinity up to 24‰ and then significantly (p ≤ .05) decreased at 32‰. The survival per cent showed a significant decrease when A. regius exposed to 8‰ salinity. An improvement with 32%, 47% and 34.1% of FCR, protein productive value and energy utilization was detected at 24‰ compared with 8‰ salinity respectively. The highest content of protein and the lowest of lipids were recorded in fish carcass at 24‰ compared with the opposite trend at 8‰ salinity. The 24‰ salinity treatment exhibited the highest value of haemoglobin (4.9 g/dl) and the lowest ratio (0.73) of albumin/globulin. The serum total protein, albumin and globulin were significantly higher at 24‰ and 32‰ salinity than those at 8‰ and 16‰ salinity groups. These findings indicate that 24‰ salinity level might be the best for meagre.     

Use of Ox‐Aquaculture© for disinfection of live prey and meagre larvae,Argyrosomus regius (Asso, 1801)

Live prey used for marine larval fish (rotifers and Artemia) as well as intensive larval rearing conditions are susceptible to the proliferation of bacteria that are the cause for reduced growth and larval mortality. Hydrogen peroxide has been recently proved a good disinfectant in aquaculture, either for eggs, larvae or live prey. In this study the effects of a hydrogen peroxide‐based product, Ox‐Aquaculture^©, on live prey (rotifers and Artemia) and meagre larvae bacterial load, composition and final status have been tested. A 34.6% reduction of total heterotrophic bacteria and 59.7% of Vibrionaceae were obtained when rotifers were exposed for 15 min to 40 mg L^?1 of the product. A 34.3% reduction of total heterotrophic bacteria and 37.7% of Vibrionaceae were obtained when Artemia were exposed for 5 min to 8000 mg L^?1 of the product. More than 95% reduction of total heterotrophic bacteria and 75% of Vibrionaceae were obtained when meagre larvae were exposed for 1 h to 20 mg L^?1 of the product. Furthermore, disinfection of enriched live prey with the product did not change the fatty acid composition and survival of the live prey and improved final larval survival.     

Incidence of systemic granulomatosis is modulated by the feeding sequence and type of enrichment in meagre (Argyrosomus regius) larvae

Systemic granulomatosis is the most frequent disease in juvenile and adult meagre, but studies regarding the first appearance of granulomas in larvae do not exist. In order to evaluate this, meagre larvae were fed four different feeding regimes as follows: RS and RO (rotifer enriched with Easy DHA Selco or Ori‐Green from 3 to 30 dph respectively), RAS and RAO (rotifer enriched with Easy DHA Selco or Ori‐Green from 3 to 21 dph and Artemia enriched with Easy DHA Selco or Ori‐Green from 12 to 30 dph respectively). All treatments were also fed with commercial microdiet from 20 to 30 dph. At 30 dph weight, length, specific growth rate and survival were significantly higher in Artemia‐fed larvae, regardless of the enrichment. Microscopic first appearance of granulomas was observed in 20 dph larvae fed RS and RO. At 30 dph granulomas and thiobarbituric acid reactive substances (TBARS), values were significantly higher in RS and RO‐fed larvae than in RAS and RAO‐fed larvae. The results showed that granulomas first appeared in meagre larvae at 20 dph when fed rotifers only. Conversely, a reduced appearance of granulomas and lipid peroxidation occurs when Artemia is included in the feeding sequence reinforcing the hypothesis of a nutritional origin of the systemic granulomatosis.     

Effect of the supplementation of live preys enriched in cod liver oil on the survival rate,growth and fatty acid profile of meagre (Argyrosomus regius) larvae

First‐feeding diets employed in the rearing of meagre (Argyrosomus regius) larvae are based on live preys that are commonly enriched to compensate for their deficiency of essential fatty acids. A feeding trial was conducted on meagre larvae (Argyrosomus regius) fed rotifer (Brachionus plicatilis) and Artemia salina enriched in lipids from an emulsion of cod liver oil (CLO) and a commercial product (CP). The effect of both enrichment products was evaluated on the survival rate, size and lipid composition of meagre larvae. The results showed that larvae fed CLO presented significant higher values of survival rate (35.0 ± 3.2%) and larval size (12.06 ± 1.17 mm) at the end of the experiment, compared to the CP diet (26.0 ± 2.5%, 11.41 ± 0.91 mm, respectively). Both zootechnical parameters were related to the content of polyunsaturated fatty acids in the larvae. Indeed, the larvae fed CLO presented a higher ratio DHA/EPA than those enriched in commercial product (0.82 ± 0.18 and 0.38 ± 0.12 at 26 days after hatching, respectively). Both larval groups presented similar body content of arachidonic acid (1.4 wt.% on average at 26 days after hatching), regardless the enrichment source. From all above, we can conclude that the enrichment of live preys with an emulsion of cod liver oil is an economically viable alternative to commercial products. Indeed, cod liver oil emulsions are able to fully meet the requirements for fatty acids of meagre larvae. Furthermore, cod liver oil is easily available from fish processing facilities.     

The interactive effects of dietary protein and energy on feed intake, growth and protein utilization of juvenile mulloway (Argyrosomus japonicus)

The objectives of this study were to describe the interactive effects of varying digestible protein (DP) and digestible energy (DE) contents on the feed intake, growth, protein utilization and whole body composition of juvenile mulloway ( Argyrosomus japonicus ) and to determine the optimal DP : DE ratio for growth. This was achieved by feeding mulloway diets containing one of four different DP levels (250–550 g kg⁻¹) at two DE levels (16 or 21 MJ kg⁻¹). Juvenile mulloway were stocked at each of two different sizes (70 or 200 g) in triplicate groups for each dietary treatment and fed twice daily to apparent satiation over 58 days. The results indicated that feed intake was not governed solely by energy demands but was also dependant on the DP content of the diet. Protein utilization did not improve with diets containing decreasing protein and increasing lipid content indicating that mulloway have a limited capacity to spare DP. Optimal DP content was found to be 444–491 g kg⁻¹ depending on the DE content of the diet and the size of mulloway and is within the range reported for other sciaenid species. The use of formulated diets with 28.6 g of DP MJ DE⁻¹ will achieve optimal growth and protein deposition for 70–275 g mulloway.     

Effects of dietary supplementation of Astragalus membranaceus,Codonopsis pilosula,and Glycyrrhiza uralensis extract mixture on growth performance,haematological parameters and hepatopancreatic performance in juvenile Pacific white shrimp (Litopenaeus vannamei)

Pacific white shrimp is the major farmed shrimp species in the world. It is known to be very sensitive to the environmental and management changes such as intensification, which is one of the primary necessities to increase shrimp production, but represents a stressful condition, and needs to be managed properly to diminish its negative effects in aquaculture. In this study, juvenile Pacific white shrimp were fed diets supplementing with equal quantities of Astragalus membranaceus, Codonopsis pilosula and Glycyrrhiza uralensis extracts in different concentrations (0, 1.0, 2.0 and 3.0 g/kg) for 8 weeks. We subsequently estimated the effects of supplemented diets on growth performance, haematological parameters, and histological changes of hepatopancreas. Results revealed that the supplemented mixture had no benefits on growth and survival rate, but had favourable effects on haemocyte count, number of granulocytes, and hemocyanin concentration in the haemolymph (p > 0.05). We observed that R cells and B cells were increased in hepatopancreatic tubules of shrimps fed on supplemented diets. Besides, a diet containing 2.0 g/kg of extract mixture maintained the decreased levels of alanine aminotransferase (p < 0.05) and aspartate aminotransferase (p > 0.05). Among the used concentrations, 2.0 g/kg seemed to be the most suitable concentration.     

Effects of dietary docosahexaenoic acid on growth performance,fatty acid profile and lipogenesis of blunt snout bream (Megalobrama amblycephala)

Six diets were designed to investigate the effects of dietary docosahexaenoic acid (22:6n‐3; DHA) levels (0.5, 1.3, 2.3, 4.2, 8.1 and 15.9 g/kg diets) on growth performance, fatty acid profile and expression of some lipogenesis‐related genes of blunt snout bream (Megalobrama amblycephala). Fish (average weight: 26.40 ± 0.11 g) were randomly fed one of six diets for 8 weeks. Results indicated that the final body weight (FBW) and specific growth rate (SGR) of fish fed 1.3 g/kg DHA were significantly higher than other groups except for the 2.3 g/kg DHA (p < .05). Compared with other groups, the number of lipid droplet clusters of the liver stained with oil red O in the 2.3 g/kg DHA group was the highest, which was consistent with the lipid contents of whole body and liver. The DHA proportion in liver and muscle significantly increased with the increasing dietary DHA levels (p < .05), which reflected fatty acid profiles of diets. The highest mRNA expressions of acetyl‐CoA carboxylase α (ACCα), fatty acid synthase (FAS) and sterol regulatory element‐binding protein‐1 (SREBP‐1) occurred in the 1.3 g/kg DHA group, followed by 2.3 g/kg DHA. In summary, the supplementation of 1.3–2.3 g/kg DHA could improve growth performance and lipogenesis, and the dietary DHA could improve DHA and PUFA proportion in liver and muscle.     

Growth performance,muscle biochemical constituents,amino acid and fatty acid compositions of the giant freshwater prawn,Macrobrachium rosenbergii,fed with herb‐incorporated diet

This study was conducted to evaluate the influence of herbs such as Ocimum sanctum, Phyllanthus amarus and Solanum trilobatum on the freshwater prawn, Macrobrachium rosenbergii, postlarvae (PL). These herbs were powdered and incorporated at 5% with the basal diet separately and in a combination. The M. rosenbergii was fed with these feeds for a period of 90 days. Results indicated that significant (P < 0.05) improvements were observed in the survival, nutritional indices (weight gain, specific growth rate and protein efficiency ratio), proximate muscle biochemical constituents (total protein, amino acid, carbohydrate and lipid), profiles of essential amino acids and fatty acids of prawns fed with herb‐incorporated feeds. Among these herbs supplemented, P. amarus produced significantly (P < 0.05) better performance followed by S. trilobatum and O. sanctum. However, prawns fed with these herbs combination showed an insignificant (P > 0.05) improvement in survival and growth performance when compared to individual supplementation. Hence, this study suggests that the herbs (O. sanctum, P. amarus and S. trilobatum) can be used as a supplementary feed for a sustainable development of freshwater prawn culture.     

Effects of different salinities on amino acid profile in Artemia franciscana

The effects of different salinity levels, including 10–15, 30–35, 70–75, 110–115 and 150–155 ppt, were evaluated on survival and the body amino acids (BAA) of Artemia franciscana. The results were expressed as total essential (TE), non‐essential (NE) and total amino acids (TAA); also, the ratio of the TE to NE (ENAA) on days 3 and 13 of the culture is reported. The study of changes in Artemia BAA showed that with the increase in the water salinity, the TE, NE and TAA increased significantly on days 3 and 13 of the culture. However, the highest ratio of ENAA was observed in the 110 gL^?1 salinity treatment on day 3 (1.067 ± 1.25). Regarding the effects of different salinity treatments on the survival rate of Artemia, it was observed that, generally, an increase in the water salinity would reduce the survival rate of this species. This reduction was observed on day 3 of culture in the salinity treatments above 120 (66.66 ± 1.68%) and below 30 gL^?1 (89.66 ± 0.34%) and on day 13 of culture in the salinity treatments below 30 (11.86 ± 0.13%) and above 70 gL^?1. Basically, it can be concluded that A. franciscana culture at a salinity of 110 gL^?1 can lead to the biological enrichment of Artemia in terms of amino acid profile.     

Comparative effects of dietary supplementation with maggot meal and soybean meal in gibel carp (Carassius auratus gibelio) and darkbarbel catfish (Pelteobagrus vachelli): growth performance and antioxidant responses

A 6‐week growth trial was conducted to investigate the effect of dietary supplementation with maggot meal (MGM) and soybean meal (SBM) on the growth performance and antioxidant responses of gibel carp (GC) and darkbarbel catfish (DC). The basal diet was formulated to contain 114 g kg⁻¹ fish meal (FM) and 200 g kg⁻¹ SBM. The basal diet was supplemented with either 280 g kg⁻¹ FM (Control), 390 g kg⁻¹ MGM or 450 g kg⁻¹ SBM to obtain three isonitrogenous (crude protein: 380 g kg⁻¹) and isocaloric (gross energy: 16 kJ g⁻¹) diets. For GC, a significant decrease in specific growth rate (SGR) was only observed in fish fed the SBM diet compared with the control (P < 0.05). Principal components analysis (PCA) of GC showed a higher similarity in antioxidant response to dietary supplementation with MGM and SBM proteins between liver and intestine, but the DC did not. The present results suggest that supplementing 390 g kg⁻¹ MGM protein to basal diet cause an enhancement of the antioxidant capacity in GC, but supplementing 390 g kg⁻¹ MGM and 450 g kg⁻¹ SBM proteins to basal diets resulted in a significant attenuation of the antioxidant capacity in DC.     

Effects of dietary fish oil replacement by microalgae raw materials on growth performance,body composition and fatty acid profile of juvenile olive flounder,Paralichthys olivaceus

Replacing dietary fish oil with DHA‐rich microalgae Schizochytrium sp. and EPA‐rich microalgae Nannochloropsis sp. for olive flounder (Paralichthys olivaceus) was examined. Three experimental isonitrogenous and isolipidic diets with lipid source provided by 50% fish oil (F50S50), 50% (M50F25S25) and 100% microalgae raw material (M100) respectively were compared with a soybean oil (S100) diet as control. Triplicate groups of olive flounder juveniles (16.5 ± 0.91 g) were fed the experimental diets, and a group was fed the control diets for 8 weeks in a recirculation system. Results showed feed efficiency and growth performance were not significantly changed when fish oil (FO) was totally substituted by soybean oil (SO) or microalgae raw material (MRM). The whole‐body composition, lipid content of liver and muscle, and lipid composition of plasma were not significantly influenced by the total substitution of FO by MRM. The polyunsaturated fatty acids (PUFA) content of muscle and liver declined in fish fed S100 diet, whereas it was not significantly reduced in fish fed M50F25S25 and M100 diets. The total substitution of FO by MRM not only maintained the levels of arachidonic acid, EPA or DHA but also increased n‐3/n‐6 ratio. In conclusion, MRM as the sole lipid source is sufficient to obtain good feed efficiency, growth performance and human health value in olive flounder juveniles.     

Effect of dietary supplementation with a synbiotic (Lacto Forte) on growth performance,haematological and histological profiles,the innate immune response and resistance to bacterial disease in Oreochromis niloticus

This study investigated the effects of a synbiotic Lacto Forte on growth performance, haemato‐immunological responses, plasma bactericidal capacity, histological profiles and resistance of Oreochromis niloticus to Pseudomonas fluorescens. The experimental fish were divided into three groups; two of them (T1 and T2) were given Lacto Forte incorporated diets at increasing level (0.7 and 1.5 g/kg, respectively) and an additive‐free basal diet served as the control (T0) for 30 and 45 days. At the end of the feeding trial, a challenge was performed using a virulent strain of P. fluorescens and mortalities were recorded over an additional 14‐days period. The results showed that Lacto Forte has a pronounced effect on haematological and growth performance parameters at 1.5 g/kg rather than 0.5 g/kg (p < 0.05). Plasma lysozyme, proteases, antiproteases and bactericidal capacity were significantly enhanced (p < 0.05) in Lacto Forte‐treated groups, particularly after 45 days of supplementation. Long‐term supplementation with Lacto Forte (1.5 g/kg) induced degenerative changes in the liver, spleen and intestine. Additionally, a significant increase (p < 0.05) in survival rates were found in Lacto Forte‐treated groups compared to the control one 14 days post‐challenge. As a result, Lacto Forte fortifies tilapia immune response and can be used as a surrogate for antibiotics to control P. fluorescens.