Total Replacement Of Fish Meal Research Articles

Fish meal replacement by Brachytrupes portentosusas for Oreochromis niloticus: Effect on growth, feed utilization, fatty acid profiles, hematology, and histological changes

In the aquaculture section, the scarcity of sustainable feed components is the major challenge. Insects may become an important, sustainable resource for expanding the raw material repertoire. Herein, this study evaluated the effects of fish meal (FM) replacement with giant cricket meal (GCM) on growth, feed utilization, fatty acids profiles, hematology, and histological changes of Nile tilapia. Five isonitrogenous and isolipidic diets were formulated with a FM-based diet (without GCM or GCM0), the other four diets were prepared to replace FM with 55, 111, 164, and 217 g/kg of GCM (referred to as GCM55 - GCM217). A total of 300 fish (approximately 7.27 ± 0.01 g/fish) were randomly allocated to triplicate groups with 20 fish per tank and fed until satiation twice daily. The results showed a linear and quadratic relationship were observed between growth parameters and dietary replacement of GCM levels. Although the total replacement of FM by GCM217 significantly diminished, but GCM55 – GCM164 replacement was higher than a control group and improved the feed conversion ratio. The condition factor was similar among dietary treatments, but the hepatosomatic index and viscerosomatic index were affected by GCM inclusion levels (P < 0.05). Whole-body dry matter and ash were linearly and quadratically increased up to GCM164, and slightly decreased in the GCM217 group. Dietary GCM inclusion regulated whole-body composition in a dose-dependent manner. Muscle fatty acids were affected by dietary GCM replacement with a linearly decreased in 18:3n-3, 20:5n-3, and 22:6n-3, and the quadratic effect was observed for 22:6n-3. Dietary inclusion of GCM quadratically increased hemoglobin, total protein, albumin, and globulin, and linearly improved red blood cell and hemoglobin levels. However, GCM inclusions higher than 164 g/kg were linearly and quadratically increased aspartate aminotransferase and alanine aminotransferase compared to a control group. A mild degree of vacuole enlargement was found in GCM164, while a high degree of irregular shape, cytoplasm vacuolization, and swelling was found in GCM217 group. In addition, intestinal morphometrics of GCM217 group detected a significantly linear and quadratic decrease in villi height. Results of the present study suggested that the dietary replacement of FM by GCM could replace up to 164 g/kg without negatively affecting growth, feed utilization, and improved blood hematology and serum proteins of Nile tilapia, even if mild histomorphological changes of hepatocytes were observed. In addition, replacing FM with GCM111 obtained the highest growth performance without any negative effects to Nile tilapia.

Haematococcus pluvialis biomass as a replacement for fish meal in the diet of Macrobrachium amazonicum post-larvae (Heller, 1862)

The current study evaluates the effect of partial or total replacement of fish meal with Haematococcus pluvialis microalgae, cultivated in an NPK culture medium, on the growth performance of Macrobrachion amazonicum shrimp post-larvae. Four diets were formulated: control (without microalgae), 25, 50 and 100% H. pluvialis replacement. Only crude protein weight gain showed no interaction and was not selected for principal components analysis. The 25% fishmeal replacement in the diet was not effective, being similar to the control. However, the complete replacement of fishmeal with H. pluvialis promoted elevated survivability, length, weight and protein retention, making it the most relevant treatment for M. amazonicum post-larvae. Therefore, it is possible to completely replace fishmeal with the microalgae H. pluvialis in the diet of M. amazonicum shrimp, which improves growth performance.

Appraisal of leaf protein concentrate derived from sugar beet and carrot as a novel fish meal substitute for juvenile Nile tilapia (Oreochromis niloticus)

Carrot and sugar beet are among the crops that produce a significant amount of leafy biomass, which raises environmental concerns. Therefore, this study aimed to evaluate the impact of replacing fish meal (FM) with sugar beet and carrot leaf protein concentrate (LPC) on performance, body composition, and blood metabolites in Nile tilapia (Oreochromis niloticus) for 84 days. Randomly, 225 tilapia fish (5.03 ± 0.006 g) were distributed into five groups having different replacement proportions of FM protein with LPC: 0 % (control diet), 25 %, 50 %, 75 % or 100 % (LPC-0, LPC-25, LPC-50, LPC-75, and LPC-100, respectively). The study found that increasing LPC replacement levels up to 75 % did not significantly alter growth performance parameters (P > 0.05). In contrast, substituting with 100 % LPC resulted in a notable reduction in the relative growth rate when compared to the control group (P = 0.043). Furthermore, fish fed the LPC-100 diet exhibited impaired trends in terms of final body weight (P = 0.064), daily weight gain (P = 0.055), and feed conversion ratio (FCR; P = 0.054). The best FCR value was observed in fish fed the LPC-75 diet. There were no significant differences in serum lipid and protein profile, liver and kidney function indicators, and hematological parameters among all groups (P > 0.05). The total replacement of FM with LPC adversely impacted the crude protein (P = 0.007) and ash (P = 0.002) contents of O. niloticus bodies. Replacing FM with 75 % LPC resulted in the highest relative margin (P = 0.008) and final margin (P = 0.005) compared to the other groups. Overall, the results indicate that 75 % of FM can be effectively replaced with LPC in O. niloticus diets, with no adverse effects observed on growth and health. Additionally, from an economic point of view, the use of LPC at 75 % instead of FM protein had more efficiency in producing healthy and low-cost aquafeed.

Genetic Identification and Traceability of Insect Meals.

Insects have been proposed as a rich alternative source of protein for the partial or total replacement of fishmeal in aquaculture. For maximum safety and effectiveness of insect meals, control of the quality composition of these products is considered mandatory. The aim of this study was the genetic analysis of the composition of commercially available insect meals at the species level. Commercially available Hermetia illucens, Tenebrio molitor and Musca domestica individuals, as well as nine insect meals produced from these species, were analyzed. The genetic identification of insects at the species level was based on a COI fragment, and analysis of the insect meals' composition was performed with the processes of cloning and colony PCR. Genetic analysis indicated that the commercially available larvae morphologically identified as Musca domestica belonged to the species Muscina stabulans. In the commercially available insect meals, no other animal species was identified beyond the expected one. However, in the insect meal produced for research purposes, fungal growth was detected. The used methodology, herein, allows for the qualitative genetic identification of insect meals and could be included in the methods of traceability of products containing insects and other animal species.

Specific Blood Plasma Circulating miRs Are Associated with the Physiological Impact of Total Fish Meal Replacement with Soybean Meal in Diets for Rainbow Trout (Oncorhynchus mykiss).

High dietary SBM content is known to induce important physiological alterations, hampering its use as a major FM alternative. Rainbow trout (Oncorhynchus mykiss) juveniles were fed two experimental diets during 9 weeks: (i) a FM diet containing 12% FM; and (ii) a vegetable meal (VM) diet totally devoid of FM and based on SBM (26%). Fish fed the VM diet did not show reduced growth performance when compared with fish fed the FM diet. Nevertheless, fish fed the VM diet had an increased viscerosomatic index, lower apparent fat digestibility, higher aminopeptidase enzyme activity and number of villi fusions, and lower α-amylase enzyme activity and brush border integrity. Small RNA-Seq analysis identified six miRs (omy-miR-730a-5p, omy-miR-135c-5p, omy-miR-93a-3p, omy-miR-152-5p, omy-miR-133a-5p, and omy-miR-196a-3p) with higher expression in blood plasma from fish fed the VM diet. Bioinformatic prediction of target mRNAs identified several overrepresented biological processes known to be associated with high dietary SBM content (e.g., lipid metabolism, epithelial integrity disruption, and bile acid status). The present research work increases our understanding of how SBM dietary content has a physiological impact in farmed fish and suggests circulating miRs might be suitable, integrative, and less invasive biomarkers in fish.

Feed cost reduction with total replacement of fish meal by soybean meal for Nile tilapia reared in biofloc system

Feed cost reduction with total replacement of fish meal by soybean meal for Nile tilapia reared in biofloc system

Total fishmeal replacement by defatted Tenebrio molitor larvae meal induces alterations in intermediary metabolism of European sea bass (Dicentrarchus labrax).

The replacement of fishmeal (FM) by insect meal (IM) in aquafeed formulation has been thoroughly studied lately, but little is known about their impact on nutrient metabolism of fish. This study evaluated the impact not only of partial but also total FM replacement by IM on intermediary metabolism of European sea bass (Dicentrarchus labrax). A fishmeal-based diet was used as a control (CTRL) and two other diets were formulated to include 20% and 40% of defatted Tenebrio molitor larvae meal (dTM), replacing 50% (TM50) and 100% (TM100) of fishmeal (FM), respectively. After a 16-week feeding trial, a multidisciplinary approach including assessment of histological, biochemical, molecular, and enzymatic parameters was adopted to investigate hepatic and plasmatic responses to the different dietary formulations. The results obtained demonstrated that dTM can be successfully used to replace 50% of FM in diets for European sea bass, without adversely affecting liver health or intermediary metabolism of nutrients. As for TM100, although no signs of steatosis were observed in the liver, the activity of glycolytic and lipogenic genes and enzymes increased when compared to CTRL diet (P < 0.05), resulting in higher levels of plasmatic non-esterified fatty acids and triacylglycerides (P < 0.05), which in the long-term may compromise fish health, thus precluding such a high degree of substitution for use in practical diets for European sea bass.

Total Replacement of Fish Meal by the Combination of Fish Residue Meal and Soy Protein from Soymilk in the Diet of Red Sea Bream (Pagrus major).

Three experiments were performed to explore (i) the complete replacement of fish meal (FM) with a combination of fish residue meal (FRM, 65% round discarded fish + 35% byproduct), soy protein concentrate (SPC) from soymilk and corn gluten meal (CGM) in Trial 1 and (ii) the utilization of diets composed of increasing byproducts in FRM in the summer (Trial 2) and winter (Trial 3) seasons. In Trial 1, the ratio of (SPC + CGM):FM in the control diet (C) was 8:2. The FM component from diet C was replaced with FRM (diet, RM20), where the ratio of (SPC + CGM):FRM became 8:2, and this ratio was changed to 6:4, 4:6 and 2:8, and referred to as RM40, RM60 and RM80, respectively. In Trials 2 and 3, the ratios of round discarded fish and byproducts in FRM were adjusted to 65:35 (FRM1), 30:70 (FRM2) and 0:100 (FRM3), and the FRM component from diet RM40 in Trial 1 was replaced with FRM1, FRM2 and FRM3 to formulate diets RM1, RM2 and RM3, respectively. In Trials 1, 2 and 3, rearing periods were 10, 8 and 12 weeks, respectively. In Trials 1 and 3, there were no significant differences in growth parameters, nutrient retention efficiency or plasma constituents among the treatments, irrespective of the inclusion levels of FRM in the diets (p > 0.05). Although there were no significant differences in final mean weight (p > 0.05), daily feeding rate and feed conversion ratio in diet RM3 were significantly higher and lower, respectively, compared to the control group in Trial 2 (p < 0.05). These results suggest that FM can be entirely replaced with FRM, and that the total elimination of round discarded fish from FRM does not affect growth or health status in red sea bream either in summer or winter seasons.

Effects of supplemental L‐methionine for total replacement of fish meal by soybean meal on growth, feed utilisation and health status of stinging catfish, Heteropneustes fossilis fry

AbstractA 14‐week feeding trial was conducted to evaluate the effect of supplemental L‐methionine for total replacement of fish meal (FM) with soybean meal (SBM) on growth and feed utilisation of the stinging catfish, Heteropneustes fossilis. Five diets were formulated, where Diet 1 contained 15% FM and 45% SBM as a source of protein. The other four diets (2–5) contained 0% FM and around 60% SBM (59.5%, 59.0%, 58.5% and 58.0% SBM, respectively) with various percentages (0.5%, 1.0%, 1.5% and 2%) of L‐methionine. The significantly highest mean final weight (g), weight gain (g), percent weight gain (%) and specific growth rate (% day−1) were found in Diet 4 containing 58.5% SBM with 1.5% L‐methionine, and there was no significant difference between Diets 1 and 4. The feed conversion ratio (FCR), protein efficiency ratio (PER) and survival rate did not differ significantly among fish groups. However, the best FCR and higher PER were found in Diet 4. The whole‐body carcass protein was significantly lower in Diets 2 and 5, which contained 0.5% and 2% L‐methionine, respectively, and might be below or above the requirements of stinging catfish. Significantly higher lipid content was found in Diets 2 and 4. Dietary 1.5% supplementation of L‐methionine for total replacement of FM with SBM increased haemoglobin, red blood cells, white blood cells and blood glucose, and 2% supplementation of L‐methionine decreased these values significantly. Moreover, considerable morphological improvement of the intestine was observed in Diet 4. Therefore, the results suggest that Diet 4 containing 58.5% SBM with 1.5% supplemental L‐methionine could completely replace FM without adverse effects on growth, feed utilisation and health condition of stinging catfish, H. fossilis.

Partial and total fishmeal replacement by defatted Tenebrio molitor larvae meal do not alter short- and mid-term regulation of food intake in European sea bass (Dicentrarchus labrax)

Understanding the underlying mechanisms responsible for regulation of food intake in fish is crucial for proper formulation of aquafeeds and consequently ensure the best growth performance of fish. Over the last decade, the study of the impact of insect meal-based diets on growth performance and voluntary feed intake of several fish species has emerged, but little is known about their influence on anorexigenic potential. This is the first study evaluating short- and mid-term responses of European sea bass (Dicentrarchus labrax) fed diets not only with partial, but also with total fishmeal (FM) replacement by defatted Tenebrio molitor larvae meal (dTM). A fishmeal-based diet was used as a control (CTRL) and two other diets were formulated to include 20% and 40% of dTM, replacing 50% and 100% of fishmeal (FM), respectively. The short-term response was evaluated after the first exposure to the experimental diets, whereas the mid-term response was evaluated after 7 days of feeding. In both short- and mid-term trials, food intake was registered. Hepatic and plasmatic metabolites and the expression of hypothalamic and telencephalic neuropeptides involved in food intake were assessed 2 and 24 h post-feeding. No differences occurred in food intake levels, neither in the short- nor mid-term. In the short-term, plasmatic glucose levels increased in fish fed TM100, regardless post-feeding sampling time. In the mid-term, fish fed TM100 had the highest levels of triglycerides in liver and the lowest levels of α-amino-acids in plasma, irrespective of post-feeding sampling time. At central level, dietary treatment did not alter the expression of neuropeptide Y (npy), agouti-related protein 2 (agrp2), pro-opio melanocortin a (pomca) or cocaine- and amphetamine-related transcript 2 (cartpt2) in hypothalamus and telencephalon. The obtained results suggest that partial and total FM replacement by dTM does not influence short- and mid-term regulation of food intake in European sea bass. Nonetheless, changes observed in hepatic and plasmatic metabolite levels of fish fed TM100 may indicate alterations of intermediary metabolism in the long-term.

Total fishmeal replacement by defattedHermetia illucens larvae meal in diets for gilthead seabream (Sparus aurata) juveniles

This work aimed to evaluate the digestibility of defattedHermetia illucens larvae meal (HM), and its effects as fishmeal (FM) replacement on growth performance, feed and nutrient utilisation, and whole-body composition of gilthead seabream (Sparus aurata) juveniles. To assess apparent digestibility coefficients (ADC) of defatted HM, a reference-diet (43% crude protein (CP); 17% crude lipid (CL)) and a test-diet, in which 30% of the reference diet was replaced with defatted HM, were formulated. To assess the effect of dietary FM replacement, four isonitrogenous (43% CP) and isolipid (18% CL) diets were formulated to include defatted HM at 0 (HM0), 15 (HM15), 30 (HM30), and 45% (HM45), replacing FM at 0, 22, 60, and 100%, respectively. Triplicate groups of fish (initial body weight of 32 g) were randomly assigned to the experimental diets and the growth trial lasted for 67 days. The digestibility trials were conducted in a digestibility system, and each diet was tested in triplicate. Protein, lipid, and energy digestibility of defatted HM were high (&gt;74%). Replacement of FM by defatted HM did not compromise the ADC of protein and lipid, while ADC of dry matter and energy increased. Complete dietary replacement of FM by defatted HM had no negative effects on growth performance, feed efficiency, whole-body composition, and protein utilisation of gilthead seabream juveniles, establishing the potential of defatted HM as an alternative ingredient for aquafeeds.

Mixed culture microorganisms fermented soybean meal improves productive performance and intestinal health of Nile tilapia ( Oreochromis niloticus ) juveniles fed plant‐based diets in a biofloc system

This study aimed to evaluate the effect of plant-based diets containing different inclusion levels (7%, 14%, 21% and 28%) of mixed culture microorganisms fermented soybean meal (FSBM) on the zootechnical performance and intestinal health of juvenile Nile tilapia (Oreochromis niloticus) reared in a biofloc system. The FSBM diets were compared with a positive control diet with fish meal and a negative control diet with no animal protein. All diets were isoprotein (33% CP) and isoenergetic (4300 kcal GE/kg). The design was completely randomized with four replications and the experiment lasted 54 days. Juveniles (1.635 ± 0.198 g) were distributed in 24 tanks (70 L) at a density of seven animals per tank. Fermentation increased probiotic microorganisms count (lactic acid bacteria 4.75 ± 0.21 log CFU g−1 and yeast 3.30 ± 0.54 log CFU g−1) and improved nutritional characteristics of FSBM. In fish fed the diet containing 7% FSBM, growth performance did not differ from fish fed the fish meal diet. FSBM inclusion improved the food efficiency of plant-based diets. The inclusions above 21% of FSBM increased the intestinal villi height. In the inclusion of 28% of FSBM, the goblet cell was higher compared to that of the other plant-based diets. The inclusion of 7% FSBM allows a total replacement of fish meal without compromising the growth performance of the animals.

Effects of fish meal replacement with Chlorella meal on growth performance, pigmentation, and liver health of largemouth bass (Micropterus salmoides)

Chlorella meal is a potential protein source for aquafeeds. However, the physiological response of carnivorous fish fed Chlorella meal remains elusive. This study evaluated the effects of replacing dietary fish meal with Chlorella meal on growth performance, pigmentation, and liver health in largemouth bass. Five diets were formulated to replace dietary fish meal of 0% (C0, control), 25% (C25), 50% (C50), 75% (C75), and 100% (C100) with Chlorella meal, respectively. Total 300 fish (17.6 ± 0.03 g) were randomly assigned to 15 tanks (3 tanks/group). Fish were fed the experimental diet twice daily for 8 weeks. The increased dietary Chlorella meal quadratically influenced the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), and feed intake (FI), which were significantly lower in the C100 group than in the other groups (P < 0.05). The feed conversion ratio (FCR) increased linearly or quadratically with dietary Chlorella meal. Dietary Chlorella meal linearly or quadratically increased the lutein content of plasma, liver, and dorsal muscle of largemouth bass (P < 0.05). Compared to the C0 group, all supplemented Chlorella meal groups significantly improved the yellowness (b∗) of the dorsal body (1.5 to 2.0 fold), abdominal body (1.5 to 1.8 fold), and dorsal muscle (3.8 to 5.4 fold) of largemouth bass (P < 0.05). In addition, compared to the C0 group, the liver vacuolation area of fish was significantly increased in the C75 and C100 groups (P < 0.05). Transcriptional levels of apoptosis-related genes of β-cell lymphoma-2 (bcl2), caspase-9-like (casp9), and caspase-3a (casp3) were markedly upregulated (0.9 to 1.6 fold) in the C100 group compared to the C0 group (P < 0.05). Based on the quadratic regression analysis between FBW, WGR, or SGR and dietary Chlorella meal level, largemouth bass had the best growth when replacing 31.7% to 32.6% of fish meal with 15.03% to 15.43% dietary Chlorella meal. The present results indicated that dietary supplementation with Chlorella meal (11.85% to 47.45%) significantly enhanced the pigmentation; however, total replacement of fish meal (40%) with Chlorella meal (47.45%) caused growth retardation, apoptosis, and liver damage in largemouth bass.

Replacement of dietary fish meal by soybean meal on growth performance, immunity, anti-oxidative capacity and mTOR pathways in juvenile abalone Haliotis discus hannai Ino

This study aimed to evaluate the effects of replacing fish meal with soybean meal (SBM) on growth performance, immunity, anti-oxidative capacity and mTOR pathway in juvenile abalone Haliotis discus hannai Ino. Five isonitrogenous (about 29% of crude protein) and isolipidic (about 4% of crude lipid) experimental diets with graded levels of fish meal replaced by SBM (0, 25, 50, 75 and 100%, respectively) were fed to abalone (initial body weight: 21.87 ± 0.07 g, initial shell length: 53.18 ± 0.18 mm) for 16 weeks. These experimental diets were named as SBM0, SBM25, SBM50, SBM75 and SBM100, respectively. The results showed that: 1) There was no significant difference in survival of abalone among all the treatments. The highest weight gain rate was found in the SBM50 group, and the group did not significantly differ from those in the SBM75 and SBM100 groups. 2) Replacement of fish meal by SBM linearly and quadratically increased the crude lipid content in muscle of abalone, which reached its highest level in the SBM50 group. 3) Trypsin activity in the digestive gland of abalone fed SBM25 diet was significantly higher than that of other groups. 4) The highest total anti-oxidative capacity and superoxidase activity in digestive gland were found in the SBM50 group. 5) The highest mRNA levels of pi3k and eif-4e, and the lowest level of 4e-bp in muscle were found in the SBM50 group. There was no significant difference in the mRNA level of mtor in the muscle among all the groups. 6). The lowest expression level of nf-κb and the highest expression level of mytimacin 6 in digestive gland of abalone were observed fed SBM50 diet. A significant quadratic trend was found in the mRNA levels of il-16 with increasing levels of dietary SBM. Meanwhile, the mRNA level of β-defensin was linearly decreased after total replacement of fish meal by SBM. Take the growth, antioxidation, immune and mTOR pathway into account, 50% replacement of dietary fish meal by SBM was recommended for abalone.

Practical diet with total replacement of fishmeal by soybean meal for Nile tilapia: growth performance and health effects

Resumo O objetivo deste estudo foi avaliar o desempenho de crescimento e saúde em juvenis de tilápia-do-nilo (Oreochromis niloticus) alimentados com dieta prática com substituição total da farinha de peixe (FP) por farelo de soja (FS), bem como o efeito na sobrevivência, após desafio patogênico com Aeromonas hydrophila. Duzentos juvenis de tilápia-do-nilo foram alojados em 8 tanques (800 L). O experimento consistiu de dois tratamentos: dieta comercial formulada com FP (controle) e dieta prática com substituição total do FP pelo FS. Foram mensuradas as variáveis de qualidade da água, parâmetros zootécnicos e hematológicos. Além disso, ao final do experimento, os peixes foram submetidos a um desafio com A. hydrophila. Maior custo por kg de peixe foi obtido no tratamento controle (com FP). A retenção de N foi maior nos peixes alimentados com dieta sem FP, enquanto os parâmetros hematológicos, imunológicos e a sobrevivência após o desafio experimental não diferiram entre os tratamentos. É possível reduzir os custos dietéticos substituindo a FP pelo FS sem afetar o desempenho do crescimento e a saúde do animal, além de beneficiar o meio ambiente ao reduzir a excreção de N na água.

Dieta prática com substituição total da farinha de peixe por farelo de soja para tilápia-do-nilo: desempenho de crescimento e efeitos na saúde

Abstract This study aimed to evaluate the growth performance and animal health in juveniles of Nile tilapia (Oreochromis niloticus) fed a practical diet with total replacement of fishmeal (FM) by soybean meal, as well the effect on survival, following pathogenic challenge with Aeromonas hydrophila. Two hundred juveniles of Nile tilapia were stored in 8 tanks (800 L). The experiment consisted of two treatments: a commercial diet formulated with FM (control) and a practical diet with total replacement of FM by soybean meal (SM). The variables of water quality, zootechnical and hematological parameters were measured. In addition, at the end of the experiment, the fish were submitted to a challenge with A. hydrophila. Higher cost per kg of fish was obtained in the control treatment (with FM). N retention was higher in fish fed a diet without FM, while hematological, immunological parameters and survival after the experimental challenge did not differ between treatments. It is possible to reduce dietary costs by replacing FM with SM without affecting growth performance or animal health, in addition to benefiting the environment by reducing the excretion of N in water.

Fishmeal replacement by periphyton reduces the fish in fish out ratio and alimentation cost in gilthead sea bream Sparus aurata

Aquaculture threatens natural resources by fishing down the sea to supply fishmeal. Alternative protein sources in aquafeeds can provide a solution, particularly those that are waste from other operations and thereby reduce feed production costs. Toward this goal, we examined the waste biomass of marine periphyton from biofilters of an integrated multi-trophic aquaculture (IMTA) system as a replacement for fishmeal in diets of gilthead seabream (Sparus aurata). Four isoproteic (41%) and isolipidic (16.7%) aquafeeds were formulated with increased content of periphyton and a corresponding decrease in fishmeal from 20 to 15, 10, or 0%. The growth and biochemical content of seabream fingerlings (initial body weight 10 g) were examined over 132 days. Replacing 50% of fishmeal by waste periphyton improved feed conversion ratio (1.2 vs. 1.35 in the control diet) without harming fish growth. The complete replacement of fishmeal with periphyton resulted in 15% slower growth but significantly higher protein content in the fish flesh (59 vs. 52% in the control diet). Halving fishmeal content reduced feed cost by US$ 0.13 kg−1 feed and saved 30% in the cost of conversion of feed to fish biomass (US$ 0.58 kg−1 produced fish vs. $0.83 in the control diet). Finally, the total replacement of fishmeal by waste periphyton in the diet reduced the fish in—fish out ratio to below 1 (0.5–0.9) as compared to 1.36 in the control diet. Replacing fishmeal with on-farm produced periphyton minimizes aquaculture footprint through the removal of excess nutrients in effluents and the use of waste biomass to reduce the ‘fish in’ content in aquafeeds and fish production costs. The present study demonstrates the great practical potential of this dual use of marine periphyton in enhancing the circular economy concept in sustainable fish production.

Total Replacement of Fishmeal by Spirulina (Arthrospira platensis) and Its Effect on Growth Performance and Product Quality of African Catfish (Clarias gariepinus)

Microalgae are increasingly being studied to replace fishmeal in aquafeed production. Low level Spirulina supplementation to various fish species has been widely investigated, demonstrating enhanced growth and better product quality. In order to evaluate the effects of a full fishmeal replacement with Spirulina (Arthrospira platensis) on growth and product quality in African catfish (Clarias gariepinus), two isoenergetic diets were formulated and fed for ten weeks to 120 fish with an average initial weight of 50 ± 3 g. Full supplementation of Spirulina resulted in reduced growth (p &lt; 0.001) whereas feed conversion ratio was on par (p &gt; 0.05). Furthermore, Spirulina-fed fish showed a more intense yellow coloration in skin, and raw and cooked fillet (p &lt; 0.001). The analysis of fatty acids revealed higher proportions of C16:0 (p &lt; 0.001) and C18:2n6 (p &lt; 0.05) in fish fed the Spirulina-diet while C24:0 (p &lt; 0.01) and C20:5n3 (p &lt; 0.001) were found to be higher in the control group. Even though no statistically significant differences in the overall SFA, MUFA and PUFA were detected, a slight increase of the n6/n3 ratio was observed in the Spirulina-fed fish. Without further optimization of the feed ration, a complete fishmeal replacement with Spirulina can lead to economic losses. It remains to be studied whether the observed changes in product quality affect consumer acceptance.

Effect of a New Feed Daphnia magna (Straus, 1820), as a Fish Meal Substitute on Growth, Feed Utilization, Histological Status, and Economic Revenue of Grey Mullet, Mugil cephalus (Linnaeus 1758)

The formulator of aquatic diets is part of a continuous search for alternative protein sources instead of depreciated fish meal. The utilization of zooplankton as a feed ingredient is an interesting trend due to their high-quality protein content and abundance of essential nutrients. The current study aims to investigate the effects of partial and total replacement of fish meal (FM) by Dahpnia magna meal (DMM) on growth performance, feed utilization, histological, and economic status of mullet, M. cephalus, larvae. In addition to the control diet, 100% FM, D0, four diets containing DMM at different levels were used: 25% (D25), 50% (D50), 75% (D75), and 100% (D100) replacement of fish meal. A total of 300 larvae (0.097 ± 0.001 g) were equally divided into five groups (three replicate per each group) at a density of 200 larvae m−3. The aquariums were renewed at a rate of 30% daily. During the 60-day experimental period, all larvae were fed their respective diets at a level of 20% of live body weight, five times a day (9.00 a.m., 12.00, 15.00, 18.00, and 21.00 p.m.). The results indicated that compared to D0, fish fed D75 recorded the highest significant value of growth, and feed utilization parameters, while fish fed D100 achieved the lowest feed cost and incidence cost, and the highest profit index and economic efficiency ratio. A strong correlation was reported among weight gain, feed conversion ratio and fish meal replacement with DMM; R2 = 0.94 and 0.91, respectively. The fit regression model representing mullet response to FM replacement with DMM is a poly-nominal regression model with maximum response at 75–100%. The histological investigation of the intestine revealed an improvement of histomorphometric indices and goblet cell number with increasing DMM inclusion levels. These findings confirmed that 75% to 100% partial substitution of FM with DMM is the ideal replacement for mullet, M. cephalus, larvae for improving fish growth performance and feed utilization.

The Effect of a Total Fishmeal Replacement by Arthrospira platensis on the Microbiome of African Catfish (Clarias gariepinus).

An increasing number of fishmeal supplements are becoming the focus of aquaculture research, with a special emphasis on microalgae/cyanobacteria such as spirulina being considered as sustainable alternatives. New feed ingredients can have a far-reaching impact on the intestinal microbiome and therefore play an important role in the development and the health of fish. However, the influence of these alternatives on the microbiome is largely unknown. We undertook a 10 weeks feeding experiment on 120 African catfish with an initial body weight of 50.1 ± 2.95 g. To understand the effect of the spirulina supplementation, two isoenergetic experimental diets were formulated, containing either fishmeal or spirulina as a protein source. The 16S rRNA sequencing was used to analyze the intestinal bacteria microbiota. Results show that the observed richness indicated no significant statistical difference, but Chao1, ACE, Shannon, and Simpson indices indicate a possible increase in bacterial richness for the spirulina diet. The most abundant bacteria in both experimental groups were Fusobacteriia with the only taxa from the genus Cetobacterium. The bacterium from genus Romboutsia was more likely to be found in the microbiome of fish fed the fishmeal diet. In spirulina-fed fish, the genera Plesiomonas and Bacteroides were the most dominant microbes observed. Even though some genera were more abundant in the spirulina group, the overall microbial community structure was not affected by diets.