This study aimed to evaluate the utilization by juvenile European sea bass of a SSFed PF mixture with Aspergillus niger CECT 2088. A 22-day digestibility and a 50-day growth trial were performed testing four diets, including 20 or 40% of an unfermented or SSFed PF mixture (rapeseed, soybean, rice bran, and sunflower seed meals, 25% each). SSF of the PF added cellulase and β-glucosidase activity to the diets. Mycotoxin contamination was not detected in any of the experimental diets except for residual levels of zearalenone and deoxynivalenol (100 and 600 times lower than that established by the European Commission Recommendation-2006/576/EC). In diets including 20% PF, SSF did not affect growth but increased apparent digestibility coefficients of protein and energy, feed efficiency, and protein efficiency ratio. On the contrary, in diets including 40% PF, SSF decreased growth performance, feed intake, feed and protein efficiency, and diet digestibility. SSF decreased the intestinal amylase activity in the 40% SSFed diet, while total alkaline proteases decreased in the 20% and 40% SSFed diets. Hepatic amino acid catabolic enzyme activity was not modulated by SSF, and plasma total protein, cholesterol, and triglyceride levels were similar among dietary treatments. In conclusion, dietary inclusion of moderate levels of the SSFed PF, up to 20%, improves the overall feed utilization efficiency without negatively impacting European sea bass growth performance. The replacement of PF with the SSFed PF mixture may contribute to reducing the environmental footprint of aquaculture production.

This study aimed to evaluate the effects of dietary inclusion of plant feedstuff mixture (PFM) pre-treated by solid-state fermentation (SSF) on the physiological responses of European seabass. For that purpose, two diets were formulated to contain: 20% inclusion level of non-fermented plant ingredients mixture (20Mix) and 20Mix fermented by A. niger in SSF conditions (20Mix-SSF). Seabass juveniles (initial body weight: 20.9 ± 3.3 g) were fed the experimental diets, reared at two different temperatures (21 and 26 °C) and subjected to weekly salinity oscillations for six weeks. Growth performance, digestive enzyme activities, humoral immune parameters, and oxidative stress indicators were evaluated. A reduction in weight gain, feed intake, and thermal growth coefficient was observed in fish fed the fermented diet (20Mix-SSF). Salinity oscillation led to an increase in weight gain, feed efficiency, daily growth index, and thermal growth coefficient, regardless of dietary treatment. Higher rearing temperatures also increased daily growth index. No dietary effect was observed on digestive enzymes activities, whereas rearing temperature and salinity oscillation modulated digestive enzyme activities. Oxidative stress responses were significantly affected by experimental diets, temperature, and salinity conditions. Catalase and glutathione peroxidase activities showed an interactive effect. Fish reared at 21 °C showed higher enzymatic activity when fed the 20Mix-SSF. Conversely, fish reared at 26 °C showed higher GPx activity when fed the 20Mix diet. Fish reared at 26 °C showed reduced peroxidase and lysozyme activities, while salinity fluctuation led to increased lysozyme activity and decreased ACH50 activity. ACH50 activity increased in fish fed the 20Mix-SSF. Overall, the dietary inclusion of PFM fermented by A. niger was unable to mitigate the impact of environmental stress on physiological performance in European seabass. In fact, fermented feed caused an inhibition of growth performances and an alteration of some physiological stress indicators.

This study investigated mealworm frass as a sustainable substrate for Pleurotus ostreatus cultivation while valorizing mushroom stems as aquaculture feed. Mushrooms were grown on substrates containing 0–15% frass, and nutritional analyses were conducted on both fruiting bodies (for human consumption) and stems (for fish feed). Increasing frass levels significantly enhanced protein content, rising from 7.78% to 22.31% in stems and 24.74% to 30.99% in fruiting bodies. Lipid concentrations showed minor fluctuations while, in contrast, β-glucan content declined with high frass inclusion percentages. Essential amino acid levels peaked at 7.37% in stems (15% frass) and 8.08% in fruiting bodies (12.5% frass). Polyunsaturated fatty acids dominated the fatty acid profile, increasing with high frass levels. Mushroom bodies and stems were additionally investigated for their antimicrobial activity to determine whether they could offer protection against common fish and human pathogens. Antimicrobial assays revealed that dichloromethane extracts from stems grown on 12.5% and 15% frass exhibited inhibitory activity (inhibition zones of 10–11 mm) against Tenacibaculum maritimum, a microorganism that poses a significant threat to aquaculture. These findings highlight mealworm frass as a promising substrate for enhancing mushroom nutritional value while providing a sustainable, protein-rich feed ingredient for aquaculture.

Fish oil has traditionally been the primary source of n-3 long-chain polyunsaturated FA (n-3 LC-PUFA) in aquafeeds but is increasingly being replaced by alternative lipid sources. However, marine carnivorous fish require dietary n-3 LC-PUFA, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which these alternative sources lack. This study assessed the long-term impact of graded levels of dietary EPA+DHA from microalgal oil on European seabass growth, feed utilization, immunological and oxidative status, and muscle FA profile. Six isoproteic (47% protein) and isolipidic (17% lipid) diets containing 0.56%, 0.66%, 0.71%, 0.90%, 1.11%, and 1.27% EPA+DHA were fed to fish (107 g initial weight) for 180 days at 23 °C, followed by a 7-day thermal challenge at 30 °C. At the end of the feeding trial, growth performance, feed utilization, organosomatic indices, blood and innate immune parameters, and oxidative stress were unaffected. Muscle FA composition mirrored that of the diets, and linear correlations were observed between muscle and dietary n-3 LC-PUFA levels. In the thermal challenge, no mortalities occurred, but hematological parameters, immune responses, and oxidative stress were intensified. Muscle FA composition remained unchanged, indicating that a dietary EPA+DHA level of 0.56% appears sufficient to meet physiological needs during an acute temperature challenge.

The yellow mealworm ( Tenebrio molitor ) is increasingly recognised as a novel feed ingredient. During industrial processing, larvae are often defatted to improve storage, handling and extrusion properties. Full-fat (ffTM) and defatted (dTM) mealworm meals were compared as total fishmeal replacements for rainbow trout ( Oncorhynchus mykiss ) diets. Three experimental diets were formulated to be isoproteic and isolipidic: a fishmeal-based control (FM) and two diets containing 25% ffTM (FFTM25) or dTM (DTM25). Juvenile rainbow trout (11.4 ± 1.5 g) were fed to apparent satiation twice daily. After 56 days, no impact on growth performance was observed. Feed intake decreased in the DTM25 and FFTM25 groups, while the feed conversion ratio was reduced in the FFTM25 diet, compared to the FM diet. In the anterior intestine, the DTM25 diet increased villus width and enterocyte height. Fish fed the DTM25 diet had higher whole-body lipid content, whereas fillet lipid content was higher in the FFTM25 group. The FFTM25 diet also increased fillet saturated and n-6 polyunsaturated fatty acids (PUFA), the thrombogenicity index and reduced the hypocholesterolemic/hypercholesterolemic ratio, while the n-3/n-6 PUFA ratio was highest in the FM diet. Nevertheless, all experimental treatments showed similar absolute levels of n-3 PUFA. Fillet yellowness was higher in the control and FFTM25 groups. Overall, the complete dietary replacement of fishmeal with both dTM and ffTM supported growth and anterior intestine health of rainbow trout juveniles. Nevertheless, the ffTM dietary inclusion improved feed efficiency, but reduced fillet lipid quality, indicating a trade-off between mealworm lipid use and product quality.