Effect of dietary medicinal herbs on lipid metabolism and stress recovery in red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

The effect of dietary medicinal herbs on lipid metabolism and stress recovery was investigated in red sea bream Pagrus major. Fish (mean body weight 24.0 ± 0.2 g) were fed on test fish meal diets supplemented with either Massa Medicata (Mm), Crataegi Fructus (Cf), Artemisia capillaries (Ac), or Cnidium officinale (Co), or with a mixture of the four herbs (HM) for 12 weeks. A control group was fed a diet without herbs in the same manner. A high survival rate was observed in the herbal diet groups. The final mean body weight, feed efficiency, protein efficiency ratio, and apparent protein and lipid retention in the Ac, Co, and HM groups were higher than those in the control and Mm groups. Final carcass, hepatic lipid and triglyceride contents, and plasma triglyceride and nonesterified fatty acid levels were lower in the Ac, Co, and HM groups compared to those of control and Mm groups. However, final hepatic phospholipid, plasma phospholipid, and high density lipoprotein cholesterol levels were higher in the Ac, Co, and HM diets groups than in the control and Mm groups. The Cf, Co, Ac, and HM groups showed faster recovery time in the 2-phenoxyethanol anesthesia test and a higher recovery rate in the 10-min air exposure test than those of the control and Mm groups. Moreover, the Cf, Ac, Co, and HM diet groups had a significantly lower plasma cortisol level than the control and Mm diet group, but the glucose level in the herbal diet groups was higher than that in the control group after a 1-h air exposure. These results indicate that the addition of medicinal herbs to the fish diet improved lipid utilization and stress recovery in red sea bream.     

Dietary medicinal herbs improve growth and some non-specific immunity of red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

The effects of dietary medicinal herbs on growth and some non-specific immunity were investigated in juvenile red sea bream Pagrus major. The fish (mean body weight 24.0±0.2g) were fed fishmeal diets supplemented with either Massa medicata (Mm), Crataegi fructus (Cf), Artemisia capillaries (Ac), Cnidium officinale (Co), or a mixture of all the herbs (HM), and a control diet without medicinal herbs, for 12 weeks. Survival, specific growth rate, feed efficiency, condition factor and hemoglobin levels were higher in fish given herbal diets than fish given the control diet without herbs. Significantly higher serum high density lipoprotein-cholesterol level and lysozyme activity were detected in HM and Co diet groups, and alternative complement pathway activity was detected in the HM diet group. However, significantly lower serum alanine aminotransferase and aspartate aminotransferase activities were obtained in all herbal diet groups compared with the control diet group. Pathogen challenge test by intraperitoneal injection of Vibrio anguillarum indicated that highest survival was obtained in the HM diet group followed by Ac, Co, Cf, and Mm diet groups. The lowest survival was obtained in the control group. These results reveal that medicinal herbs in diets enhance growth and some non-specific immunity of red sea bream.     

Evaluation of micronized lupin seed meal as an alternative protein source in diets for gilthead sea bream Sparus aurata L. juveniles

A 12‐week growth trial was performed to evaluate the effect of lupin seed meal as a protein source in diets for gilthead sea bream (Sparus aurata) juveniles. Six experimental diets were formulated to be isonitrogenous and isoenergetic and to contain 10%, 20% and 30% of raw lupin (Lupinus angustifolius) seed meal protein or 20% and 30% lupin (L. angustifolius) seed meal processed by infrared radiation (micronized) in place of fish meal protein, the only protein source of the control diet. Fish accepted all diets well and no significant differences in feed utilization among groups were noticed during the trial. Final weight of fish fed the experimental diets was identical or higher than the control group. Final weight of fish fed diets including 20% micronized lupin protein was even significantly higher than that of fish fed the fish meal‐based control diet. Moreover, at the same dietary lupin seed meal protein inclusion levels, final weight of fish fed diets including micronized lupin was significantly higher than with raw lupin. A trend was also noticed for a decrease of final weight with the increase in lupin seed meal in the diets. At the end of the trial no significant differences in proximate whole‐body composition, hepatosomatic and visceral indices were observed among groups. It is concluded that lupin seed meal can replace up to 30% fish meal protein in diets for gilthead sea bream juveniles with no negative effects on growth performance. Furthermore, micronization of lupin seeds improves its dietary value for gilthead sea bream juveniles. At the same dietary lupin inclusion levels, diets including micronized lupin seeds promote significantly higher growth rates than raw lupin seeds.     

Validation of processed animal proteins (mono‐PAPS) in experimental diets for juvenile gilthead sea bream (Sparus aurata L.) as primary fish meal replacers within a European perspective

Experimental diets were formulated to evaluate a “pure” poultry meat meal (PMM) source in diets formulated for juvenile gilthead sea bream (Sparus aurata L.). The digestible protein contribution of fish meal in a control diet was substituted by 25%, 50% and 75% of a processed poultry meat meal (PMM) on a digestible crude protein (DCP) basis and by 5% and 10% for an enzyme‐treated feather meal (EFM) and also a spray‐dried haemaglobin meal (SDHM), respectively. In a consecutive trial, diets were designed to assess the value of a “pure” (defatted) poultry protein substituting the fish meal (FM) protein content. Experimental diets included: a control diet, two test diets where 75% of FM was replaced by a full‐fat PMM (PMM75) or a defatted grade of PMM (dPMM75) and two test diets where 50% of FM was substituted for defatted PMM (dPMM50) or a 50:50 blend of soya bean meal and defatted PMM (SBM/dPMM) to produce a composite product. This soya bean/dPMM blend was tested to enhance the nutritional value of this key plant ingredient commonly employed in sea bream diets that can be deficient in specific amino acids and minerals. In the first trial, gilthead sea bream grew effectively on diets containing up to the 75% replacement of FM attaining a mean weight of 63.6 g compared to 67.8 g for the FM control fed group. For the consecutive trial, the fishmeal‐based control diet yielded the highest SGR followed by dPMM50 and SBM/dPMM blend inclusion but was not significant. Carcass FA profiles of gilthead sea bream conformed to the expected changes in relation to the dietary FA patterns, with the 18:1n‐9 representative of the poultry lipid signature becoming more apparent with PMM inclusion. The ratio of n‐3/n‐6 fatty acids was greatly affected in sea bream fed the full‐fat PMM at 75% inclusion due to fish oil exclusion. Defatted dPMM, however, allowed more of the fish oil to be used in the diet and reducing this latter effect in sea bream carcass, hence restoring the higher total omega‐3 HUFA fatty acids namely EPA and DHA and n‐3/n‐6 ratio. It is concluded that poultry meat meal can be modestly incorporated into formulated diets for sea bream and can be used in conjunction with soya bean meal without any fundamental changes in performance and feed efficiency.     

Soybean meal can partially replace enzyme-treated fish meal in the diet of juvenile Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis>

This study was carried out to investigate whether expensive enzyme-treated fish meal (EFM) can be partially replaced by soybean meal (SM) or enzyme-treated SM (ESM) without compromising the growth of captive-raised Pacific bluefin tuna (PBT) juveniles. Five fish diets were tested: EFM (control) and EFM in which 10 or 20% of the EFM was replaced with either ESM or SM (ESM₁₀, ESM₂₀, SM₁₀ and SM₂₀, respectively). The respective diets were provided to 28-day-old PBT juveniles (mean body weight approx. 0.38 g) stocked randomly in 15-m³ tanks (276 juveniles per tank; two tanks per treatment) for 12 days. The final mean body weight of PBT juveniles on diets EFM, SM₁₀, and SM₂₀ was significantly higher than that of juveniles on diet ESM₂₀. Although daily feeding rate was significantly higher in the ESM and SM groups, feed efficiency (FE) was significantly higher in the EFM group; there was no significant difference between juveniles fed diets EFM and SM₁₀. Protein and phosphorus retention efficiency were significantly lower in the ESM₂₀, and ESM₂₀ and EFM groups, respectively. Phosphorus discharge was significantly lower in the SM groups. The results demonstrate that 10% SM (11% EFM replacement) can be included in EFM without compromising the growth performance of PBT juveniles.     

Partial Replacement of Fish Meal by Fermented Soybean Meal in Diets for Black Sea Bream,Acanthopagrus schlegelii,Juveniles

The effect of fish meal (FM) substitution with fermented soybean meal (FSBM) in the diets of the carnivorous marine fish, black sea bream, Acanthopagrus schlegelii, was investigated. An 8‐wk feeding trial was conducted with black sea bream (11.82 ± 0.32 g; mean initial weight) in indoor flow‐through fiberglass tanks (25 fish per tank). Six isonitrogenous and isoenergetic diets were formulated, in which FM was replaced by FSBM at 0% (control diet), 10% (FSBM10), 20% (FSBM20), 30% (FSBM30), 40% (FSBM40), or 50% (FSBM50), respectively. Each diet was fed to triplicate groups of fish twice daily to apparent satiation. The results showed that there was no difference in survival of black sea bream during the feeding trial. Fish fed the FSBM10 or FSBM20 diet showed comparable growth performance compared with fish fed the control diet (P > 0.05), whereas more than 30% replacement of FM adversely affected weight gain and specific growth rate (P < 0.05). Feed intake was significantly lower for fish fed the FSBM50 diet compared with fish fed the control diet. Feed conversion ratio (FCR) tended to increase with increasing dietary FSBM with the poorest FCR observed for fish fed the FSBM50 diet. Protein efficiency ratio and protein productive values showed similar patterns. Apparent digestibility of nutrients significantly decreased with increasing dietary FSBM level. With the exception of protein content, no significant differences in whole body and dorsal muscle composition were observed in fish fed the various diets. Fish fed the FSBM50 diet had significantly lower intraperitoneal ratio than fish fed the control or FSBM10 diet. Hepatosomatic index and condition factor were unaffected by dietary treatments. This study showed that up to 20% of dietary FM protein could be replaced by FSBM protein in the diets of juvenile black sea bream.     

Effects of dietary animal proteins on growth and body composition of the red drum (Sciaenops ocellatus)

Two experiments were conducted to determine the nutritional value of various dietary proteins for juvenile red drum. In the first 8-week feeding trial, diets containing similar quantities of lipid, carbohydrate, available energy and ash with 35% crude protein from either lyophilized whole-body croaker (Micropogon undulatus), striated beef muscle, red drum processing waste or commercially processed menhaden (Brevoortia tyrannus) fish meal were fed to juvenile red drum in brackish (6 ppt) water along with a control diet containing lyophilized muscle of red drum. The control diet produced significantly (P<0.05) greater weight gain (WG), feed efficiency (FE), and protein efficiency ratio (PER) values than all other diets; intermediate responses were observed for fish fed diets containing protein from red drum waste and whole-body croaker, while diets containing striated beef muscle and menhaden fish meal yielded the lowest values. Some differences in tissue indices and body composition of red drum including hepatosomatic index, whole-body ash and lipid, as well as liver lipid and glycogen were induced by the various diets. In the second 8-week feeding trial, the control diet containing red drum muscle was compared with similar diets containing protein from whole-body croaker and menhaden fish meal. Again the control diet produced the greatest WG, FE, and PER values followed by whole-body croaker and then menhaden fish meal. Effects of the dietary proteins on tissue indices and body composition were limited. The excellent protein quality and low-temperature processing of lyophilized red drum muscle resulted in superior performance of red drum relative to the other evaluated protein products, and lyophilized whole-body croaker provided better performance than commercially processed menhaden fish meal.     

Effects of partial substitution of dietary fish meal by fermented soybean meal on growth performance,amino acid and biochemical parameters of juvenile black sea bream Acanthopagrus schlegeli

A feeding trial was conducted to evaluate the effect of replacing fish meal protein with fermented soybean meal (FSM) on the growth performance, feed utilization, amino acid profile, body composition, morphological parameters, activity of antioxidant and digestive enzymes of black sea bream (Acanthopagrus schlegeli) juvenile. Five isonitrogenic and isolipidic diets were prepared with levels of 0 (control), 80, 160, 240 and 320 g kg^?1 FSM. Triplicate groups (40 fish per tank) of juvenile black sea bream with initial weight of 1.17 ± 0.04 g were hand‐fed to visual satiation at three meals per day for 8 weeks. The fish fed diets containing different levels of FSM had no significant differences regarding survival and specific growth rate compared with control group. Feed and protein efficiency ratios of fish fed diet containing 320 g kg^?1 FSM were significantly lower than those of control group. Daily feed intake and daily protein intake of fish fed diet containing 240–320 g kg^?1 were significantly higher than those of control group. Hepatosomatic index and condition factor of fish were not affected by different dietary FSM level. Fish fed diets containing 240–320 g kg^?1 FSM had significantly higher visceral somatic index than control group. Whole body proximate and amino acid compositions of fish were not affected by dietary FSM level. The activity of digestive enzymes in the intestine was not affected by dietary FSM level. The activity of glutathione peroxidase in liver was significantly higher for fish fed the diet containing 160 g kg^?1 FSM compared with control group. This study showed that up to 40% fish meal in the diets of juvenile black sea bream could be replaced by fermented soybean meal with supplementation of methionine, lysine and taurine.     

Potential of local agricultural by-products for the rearing of African catfish Clarias gariepinus in Rwanda: effects on growth, feed utilization and body composition

This study was performed to evaluate the effect of replacing fish meal with local by‐products on Clarias gariepinus growth performance, feed utilization and body composition. A control diet contained 50% of fish meal. In four other diets, fish meal was partially replaced by vegetable and animal protein blend composed of sunflower oil cake, soybean oil cake, groundnut oil cake, bean meal, chicken viscera and blood meal. The study was conducted in a recirculating water system at a mean temperature of 23.6°C. The five test diets were compared with a commercial diet developed for African catfish. All diets were balanced to be equal in gross energy (19 kJ g⁻¹) and crude protein (40%). The experimental groups were fed in triplicate for 8 weeks, increasing fish weight from about 6.2 g at start to 52.3 g in the end. Best specific growth rate (SGR=3.4), feed efficiency (FE=1.3) and protein efficiency ratio (PER=3) were obtained with the control diet (diet 50% fish meal), although there were no significant differences between the group of fish fed the control diet and those fed diets based on groundnut oil cake or bean meal, whereas SGR (2.17), FE (0.85) and PER (1.95) were significantly (P<0.01) lower in fish fed diet containing sunflower oil cake. No significant differences (P<0.05) were found in fish fed commercial diet and diets containing bean meal or groundnut oil cake. Groundnut oil cake or bean meal can thus replace at least 50% of fish meal in the diet of Clarias fingerlings without amino acid supplementation. Because of its economic importance and its potential in animal nutrition sunflower oil cake is still an interesting feed ingredient, but its efficiency should be improved by various processing techniques. African catfish can utilize efficiently a diet with low percentage of animal protein without growth reduction.     

Evaluation of corn gluten meal as a protein source in diets for gilthead sea bream (Sparus aurata L.) juveniles

A 12‐week growth trial was conducted to evaluate corn gluten meal as an alternative protein source to fish meal in diets for gilthead sea bream juveniles. The experimental diets were formulated to be isonitrogenous and isoenergetic and to have 20%, 40%, 60% and 80% of fish meal protein, the only protein source in the control diet, replaced by corn gluten meal. At the end of the growth trial only the group fed the diet with 80% corn gluten protein exhibited significantly reduced growth and feed efficiency compared with the fish meal‐based diet. This was most likely due to a dietary amino acid deficiency in that diet. A trend was noticed for feed efficiency to improve with the replacement of fish meal protein in the diets up to 60%. There were no significant differences among groups in protein and energy retention (as percentage of intake). At the end of the trial whole body water content of the experimental groups was significantly lower and the lipid content of groups including 60% and 80% corn gluten protein was significantly higher than that in the control. No other differences were observed in whole body composition among groups. Apparent digestibility coefficients (ADC) of the diets were evaluated in a separate trial. The ADC of dry matter of the experimental diets was significantly higher than in the control diet; there were no significant differences among diets in the ADC of energy and protein, except for the ADC of protein of diet with 80% corn gluten protein, which was significantly lower than the control. The results of this study indicate that corn gluten meal can replace up to 60% fish meal protein in diets for gilthead sea bream juveniles with no negative effects on fish performance.     

Nutrient digestibility profile of premium (category III grade) animal protein by-products for temperate marine fish species (European sea bass, gilthead sea bream and turbot)

Three trials, with classical experimental designs for in vivo digestibility studies, were conducted to determine the apparent digestibility coefficient (ADC) of protein (ADCp), lipid (ADCl), energy (ADCe) and amino acids (AA) in selected animal by-products fed to European sea bass, Dicentrarchus labrax (Trial 1), gilthead sea bream, Sparus aurata (Trial 2), and turbot, Psetta maxima (Trial 3). In each trial, five experimental diets [including a reference diet (RD)] where fish meal (FM) was used as the sole protein source were fed ad libitum to the fish for a period of 4 weeks. Test diets were based on the FM RD and obtained by replacing 30% of the RD with a category III designated European animal by-products (fit for human consumption), namely: steam hydrolysed feather meal (HFM), enzyme-treated feather meal (EFM), poultry meat meal (PMM) and spray-dried haemoglobin meal (SDHM). Faecal material was collected using the 'Guelph system', and nutrient and energy digestibility coefficients were related to the measurement of chromic oxide (Cr₂O₃) incorporated into the diet at a rate of 0.5%. Without any exception, FM diets yielded the best digestibility values for all macro-nutrients and by all fish. Among the test ingredients, ADCp was consistently higher for PMM and SDHM in the three species (85.5%, 91.1% in sea bass; 79.2%, 82.8% in sea bream; and 78.4%, 74.8% in turbot). Conversely, ADCp of HFM and EFM were less efficiently digested (67.2%, 68.2% in sea bass; 21.5%, 21.7% in sea bream; and 46.6%, 36.0% in turbot). However, the novel processing method applied to feather meal did not considerably influence the digestibility of most of the nutrients in this feedstuff. The current investigation yielded valuable numerical ADC for EAA considered to be of prime importance in generating balanced diet formulations.     

Assessing feasibility of replacement of fishmeal with enzyme‐treated feather meal in the diet of juvenile turbot (Scophthalmus maximus L.)

A feeding trial was conducted to examine the potential of enzyme‐treated feather meal (EFM) as a fishmeal substitute in the diet of turbot. Fishmeal (650 g/kg) was incrementally replaced (0, 160, 320, 480, 640 and 800 g/kg) by EFM (0, 80, 160, 240, 320, 400 g/kg) to prepare six experimental diets (Control, EFM8, EFM16, EFM24, EFM32 and EFM40). Diet EFM24 was supplemented with lysine and methionine to form seventh diet (EFM24 + AA). The eighth diet was formulated with 240 g/kg steam‐processed feather meal to replace 480 g/kg fishmeal (SFM24). Eight diets were each fed to triplicate groups of juvenile turbot (37.47 g) in a recirculating aquaculture system for 7 weeks. The results showed that fish fed diet EFM24 grew better than those fed SFM24 (p < .05). The growth performance, body composition and serum biochemical indices of fish fed diet EFM8 were not statistically different compared to the control treatment (p > .05). However, further increase in fishmeal replacement (32%–80%) affected negatively growth, nutrients digestibility, serum biochemical indices and body composition (p < .05). Supplementation of lysine and methionine (EFM24 + AA) significantly improved growth performance and diet utilization compared to EFM24 (p < .05). Altogether results suggested that the EFM could comprise 80 g/kg in a diet for juvenile turbot by concurrent reduction of the fishmeal content by 160 g/kg without lysine and methionine supplementation.     

Dietary supplementation with Mannanoligosaccharides (MOS) from Bio‐Mos enhances growth parameters and digestive capacity of gilthead sea bream (Sparus aurata)

Dietary mannanoligosaccharide (MOS) from commercial product, Bio‐Mos supplementation, has been examined for its effects on weight gain and feed conversion of domestic mammals and birds, but very few studies have evaluated the responses of aquacultural species to MOS. A feeding and digestibility trial was performed to asses the potential beneficial effect of two levels of Bio‐Mos on growth, feed utilization, survival rate and nutrients’ digestion of gilthead sea bream (Sparus aurata) with an initial average weight of 170 g. Bio‐Mos was added at 2 or 4 g kg^?1 to a fish meal–based control diet, and each diet was fed to triplicate groups of 1‐year‐old gilthead sea bream. After 12 weeks, there were no differences in survival rate among fish fed experimental diets (P > 0.05). It was observed that a significant improvability existed for both growth and feed utilization in fish fed diets supplemented with Bio‐Mos (P < 0.05). Body proximate composition remained unaffected by Bio‐Mos supplementation in fish fed experimental diets (P > 0.05). Apparent digestibility values for protein, carbohydrate and energy were appreciably affected by the inclusion of two different levels of Bio‐Mos, only lipid digestibility was the exception. In conclusion, the results of this trial indicate that 2 g kg^?1 dietary supplementation with BIO‐MOS seem to be most positive for gilthead sea bream production.     

Evaluation of Experimental and Practical Diets for Bluegill Lepomis macrochirus and Hybrid Bluegill L. cyanellus × L. macrochirus

Two experiments were conducted to identify appropriate experimental and practical diets for bluegill Lepomis macrochirus and hybrid bluegill L. cyanellus × L. macrochirus reared in aquaria. In the first study, four experimental diets and five commercial diets were evaluated in juvenile hybrid bluegill initially weighing 4.8 g/fish. The experimental diets contained casein (CAS), casein + gelatin (CAWGEL), casein + L‐arginine‐HCI (CAS/ARG), or casein + gelatin + crystalline amino acids (CAS/AA) as sources of crude protein. The commercial diets included three diets formulated to meet the nutritional requirements of rainbow trout Oncorhynchus mykiss and two diets formulated to meet the nutritional requirements of channel catfish Ictalurus punctatus. Each diet was fed twice daily at a rate of 4% of body weigh/d to triplicate groups of fish. At the end of the 8‐wk feeding trial, weight gain was significantly higher in fish fed the best commercial rainbow trout diets (205–217%) compared to fish fed diets formulated for channel catfish (87–104%). Weight gain and feed efficiency (FE) of fish fed the experimental diets (5346% and 0.19–0.32, respectively) were significantly lower than those of fish fed the commercial rainbow trout diets (143–217% and 0.49–0.64, respectively). In the second experiment, the same dietary treatments were fed for 8 wk to juvenile bluegill initially weighing 3.7 g/fish. Each diet was fed twice daily at a rate of 4% of body weight/d to triplicate groups of fish. Weight gain was significantly higher in fish fed commercial trout diets (291–402%) compared to fish fed diets formulated for channel catfish (164–191%). Weight gain and FE of fish fed CAS/ARG were significantly higher than those of fish fed the commercial catfish diets, but significantly lower than those of fish fed the best commercial trout diets. Results of this study indicate that commercial rainbow trout diets are preferable to commercial channel catfish diets for culture of bluegill and hybrid bluegill. More research is needed to identify appropriate experimental diets for this group of fishes.     

Effects of dietary taurine levels on epidermal thickness and scale loss in red sea bream,Pagrus major

Taurine is often added to artificial fish diets to compensate for a reduction in fish meal (FM). However, the taurine content of FM‐based diets is typically lower than in diets consisting of raw fish, even in diets where FM is the only protein source. We evaluated the effects of dietary taurine in FM‐based diets on epidermal thickness and scale detachability in red sea bream Pagrus major. We compared the effect of diets containing 0% (control), 0.3% (Tau‐0.3%), 0.6% (Tau‐0.6%) and 1.0% (Tau‐1.0%) taurine. Red sea bream (average body weight, 39 g) were fed these diets for 7 weeks. Taurine supplementation had no effect on growth, feed intake, feeding efficiency, or survival. However, the epidermal thickness was higher in fish in the Tau‐0.6% and Tau‐1.0% groups than in the control and Tau‐0.3% groups. Similarly, scale loss was significantly higher in the control group than in the Tau‐0.6% and Tau‐1.0% groups. Our results suggest that supplementation with >0.6% taurine (1.0% in diet) improves skin condition.     

Soybean meal as a protein source in gilthead sea bream (Sparus aurata L.) diets: effects on growth and nutrient utilization

The value of defatted soybean meal as a protein source for sea bream fingerlings (15.2±4.4 g on average) growing to market size (300–350 g) was evaluated by feeding extruded isonitrogenous and isoenergetic diets (46% protein and 22 MJ kg⁻¹) containing 20%, 30%, 40% and 50% soybean meal considering two phases. On day 87, the fish weight ranged between 66 and 81 g. The specific growth rate (SGR) of sea bream fed 50% soybean was lower (1.73% day⁻¹) than that of fish fed 20% (1.87% day⁻¹) and 30% (1.93% day⁻¹), but the food conversion ratio (FCR) was not significantly affected, and a quadratic significant trend was observed for the feed intake (FI) in relation to the dietary soybean level. At the end of the second phase on day 309, fish weight was between 303 and 349 g, but SGR and FCR were similar for all diets, and ranged between 0.64 and 0.69% day⁻¹, and 1.95 and 2.10% day⁻¹ respectively. The final biometric parameters were not affected by the diets, although the levels of some free amino acids in the muscle were affected. Sensory differences were detected by panellists in fish fed diet 20% as compared those fed diet 50%, which had a less marine flavour and was less juicy. The global growth results suggest the possibility of feeding sea bream weighing less than 80 g with 30% soybean meal, and for fish weighing more than 80 g, a 50% dietary soybean meal can be used until the fish reach commercial weight, with no negative effects on growth or feed efficiency. Nevertheless, when sensory analysis and economic aspects are considered, the maximum inclusion level of soybean was 20–22%.     

Availability of black soldier fly meal as an alternative protein source to fish meal in red sea bream (Pagrus major,Temminck & Schlegel) fingerling diets

Black soldier fly meal (BM) is an outstanding candidate as a fish meal (FM) substitute because it contains relatively high protein and essential amino acids. In this study, we replaced FM in red sea bream diets (Pagrus major) with BM to investigate its effect on growth and feed utilization. Six isonitrogenous and isolipidic experimental diets were prepared by substituting 0%, 20%, 40%, 60%, 80% and 100% FM protein with BM (Control, BM20, BM40, BM60, BM80 and BM100, respectively). After the 8-week feeding trial, final body weight, weight gain, specific growth rate and feed efficiency decreased linearly with increasing dietary BM level (p < 0.05). Apparent digestibility of protein and fat and serum total cholesterol concentration decreased with increasing dietary BM levels (p < 0.05) Final body weight, WG, SGR and FE against dietary BM level had breaking points of 76.2%, 41.7%, 76.5% and 60.0%, respectively, in segmental regression analysis. In conclusion, the results suggest that BM can replace a maximum of 41.7% of FM in the diet of red sea bream without compromising growth performance or feed efficiency for 56 days.     

Sensory Analysis of Rainbow Trout,Oncorhynchus mykiss,Fed Enriched Black Soldier Fly Prepupae,Hermetia illucens

A growth trial and fillet sensory analysis were conducted to examine the effects of replacing dietary fish meal with black soldier fly (BSF) prepupae, Hermetia illucens, in rainbow trout, Oncorhynchus mykiss. A practical‐type trout diet was formulated to contain 45% protein; four test diets were developed by substituting 25 and 50% of the fish meal with normal (BSF) or fish offal‐enriched black soldier fly (EBSF) prepupae. Dietary fat was adjusted to approximately 20% lipid using fish oil and poultry fat. Diets were fed to three replicate tanks of fish per treatment (10 fish/tank) for 8 wk. After the trial, three fish per tank were sampled for determination of hepatosomatic index, intraperitoneal fat ratio and muscle ratio, and muscle proximate and fatty acid composition. Fish remaining after sampling were used for sensory evaluation. Growth of fish fed the EBSF diets was not significantly different from those fish fed the fish meal‐based control diet, while the growth of fish fed the BSF diets was significantly reduced as compared to the control diet. A group of 30 untrained panelists did not detect a significant difference in a blind comparison of fish fed the fish meal containing control diet as compared to fish fed the EBSF or BSF diets.     

Growth,tissue metabolites and digestive functionality in Sparus aurata juveniles fed different levels of macroalgae,Gracilaria cornea and Ulva rigida

The aim of this study was to evaluate the inclusion of two macroalgae as dietary ingredients on growth, body composition, intermediate metabolism, intestinal enzymes and gut histology of Sparus aurata juveniles. Six isocaloric and isonitrogenous diets incorporating 5%, 15% or 25% of Gracilaria cornea or Ulva rigida meal were tested against a control diet. Duplicate groups of fifteen fish (14 g) were fed the experimental diets for 70 days. Growth performance showed an inverse linear relationship with the inclusion level of Gracilaria. Feed conversion ratio increased significantly in fish fed 25% Gracilaria. Ulva presented a quadratic relationship with the lowest SGR at 15% of inclusion. Fish fed 25% Ulva exhibited significantly lower lipid content than those fed control diet. Overall, metabolites did not show differences with specimens fed control diet, except for plasmatic glucose and muscle lactate. Intestinal proteolytic activity was reduced with the macroalgae inclusion level, but all fish showed the same enzyme pattern. The histological study revealed no negative effect on liver and intestine structure by the macroalgae inclusion. The present work demonstrated that these ingredients can be used in practical diets for sea bream, but a more comprehensive research is needed to determine the optimum dietary level in a longer feeding trial.     

Studies on the green liver in cultured red sea bream fed low level and non-fish meal diets: Relationship between hepatic taurine and biliverdin levels

SUMMARY: The aim of this study was to investigate the cause of green liver in red sea bream fed substitute protein diets. Red sea bream Pagrus major was given either of the following diets for 28 weeks: (1) control diet (50% fish meal), (2) low level fish meal diet (15% fish meal), and (3) non-fish meal diet (0% fish meal). The green liver was observed in all groups tested, but the incidence was much higher in the experimental diet groups. The feeding of substitute protein diets reduced plasma triglyceride and cholesterol levels. However, there was no significant difference in plasma hepatic enzyme activities and plasma bile salts concentration among the treatments. Fish fed the substitute protein diets showed low hepatic taurine levels with an appearance of a biliverdin in the liver. Moreover, the proportion of ditaurobilirubin to total biliary bile pigments was significantly lower in fish fed the substitute protein diets. These data indicate that feeding of substitute protein diets did not induce any cholestatic hepatobiliary obstructions and that the low hepatic taurine level was one of the probable factors responsible for the occurrence of green liver in red sea bream fed substitute protein diets.