Zebrafish are one of the most used animal models in biological research and a cost-effective alternative to rodents. Despite this, nutritional requirements and standardized feeding protocols have not yet been established for this species. This is important to avoid nutritional effects on experimental outcomes, and especially when zebrafish models are used in preclinical studies, as many diseases have nutritional confounding factors. A key aspect of zebrafish nutrition is related to feed intake, the amount of feed ingested by each fish daily. With the goal of standardizing feeding protocols among the zebrafish community, this paper systematically reviews the available data from 73 studies on zebrafish feed intake, feeding regimes (levels), and diet composition. Great variability was observed regarding diet composition, especially regarding crude protein (mean 44.98 ± 9.87%) and lipid content (9.91 ± 5.40%). Interestingly, the gross energy levels of the zebrafish diets were similar across the reviewed studies (20.39 ± 2.10 kilojoules/g of feed). In most of the reviewed papers, fish received a predetermined quantity of feed (feed supplied). The authors fed the fish according to the voluntary intake and then calculated feed intake (FI) in only 17 papers. From a quantitative point of view, FI was higher than when a fixed quantity (pre-defined) of feed was supplied. Also, the literature showed that many biotic and abiotic factors may affect zebrafish FI. Finally, based on the FI data gathered from the literature, a new feeding protocol is proposed. In summary, a daily feeding rate of 9–10% of body weight is proposed for larvae, whereas these values are equal to 6–8% for juveniles and 5% for adults when a dry feed with a proper protein and energy content is used.

For improving aquafeed sustainability, insect meal is currently considered the most promising alternative to fishmeal. However, in this regard, more data are still necessary to avoid possible negative impacts on fish growth performance, metabolism, and welfare. The present study investigated the effects of increasing the inclusion of Hermetia illucens meal (0%, 17%, 33% and 50% of the feed, equating to 0%, 34%, 66% and 100% fishmeal replacement) on fish mortality, growth performance, intestine morphology, and gene expression of intestinal carriers. The results showed no adverse effects on fish mortality, feed intake and body weight and a positive effect on feed conversion ratio. Body weight gain was higher when 17% and 50% of Black soldier fly meals’ feed included (34% and 100% fishmeal replacement, respectively). Gut morphology was not affected by the dietary treatments except for the area of PAS-positive goblet cells that was higher in the treatment fed 33% of insect meal. The mRNA expression of intestinal epithelium functionality-specific marker genes, such as slc15a1 (alias pept1, alias slc15a1b), gata4 and nfkb1b, confirmed that the insect meal-based diets might replace fishmeal-based diets without negative effects. Overall, the results of the present study suggest that using Hermetia illucens larvae meal as a replacement for fishmeal in aquafeeds might help to enhance sustainability while assuring favorable fish growth performance and gut health.

The aquaculture sector has seen significant growth recently but also faces sustainability challenges due to the use of fish meal and fish oil. This project explored the potential of using partially defatted Hermetia illucens (black soldier fly) larvae meal (BSFL meal) as a sustainable alternative to fish meal in Sparus aurata diets. The trial was conducted with 132 fish reared in six tanks and fed two aquafeeds: a standard (CTRL) and an experimental (IF) in which fish meal was replaced (10%) with partially defatted BSFL meal. Fillets were analysed for chemical composition, elemental composition, fatty acid (FA) profile, primary and secondary oxidative products, cholesterol, pH and colour. Moreover, a panel of food experts (n = 26) was involved in a discrimination sensory test (duo–trio test) on raw and cooked fillets. The results showed no differences in chemical and physical analyses. The FA profile of IF was characterised by a significantly higher content of lauric acid (p-value 0.009) and myristic acid (p-value 0.049) than the CTRL ones. The panellists correctly identified the raw samples and found differences. On the other hand, only about 50% of the assessors correctly identified the cooked samples. The overall results suggest that partially defatted BSFL meal may represent a valid alternative for aquafeed production that could affect the sensory properties of raw fillets without altering their nutritional composition.