Mealworm (Tenebrio molitor) potencial in fish nutrition: a review

The creation of aquatic organisms it is constantly growing and with this comes the need to meet this demand with the increased production of inputs such as feed for aquaculture. Fish nutrition is mainly characterized by the use of fish meal and oil for the manufacture of rations for their food. Soybean bran is the second most used ingredient as a source of protein in the production of feed for aquaculture. However, these ingredients compete with other feed segments, increasing cost or reducing market availability. Therefore, alternative sources of protein must be studied and developed to meet this demand. In this sense, insects present themselves as sources of high quality protein, in addition to fatty acids, vitamins and minerals. Although there is a problem with large-scale production to meet the demand of the feed market, the ease of breeding certain species of insects is capable of making this reality possible. Thus, insects can be a likely alternative protein source in fish feed, replacing conventional sources. This review aims to evaluate the inclusion of mealworm in the fish diet, in terms of performance and discuss the results obtained.

Performance of Co-Housed Neon Tetras (Paracheirodon innesi) and Glowlight Rasboras (Trigonostigma hengeli) Fed Commercial Flakes and Lyophilized Natural Food

Little to no research has been conducted thus far regarding aquarium fish nutrition. In order to ensure the welfare of house-kept ornamentals, such studies should take into account that there are distinct biological differences occurring between different fish species/taxa, especially in regard to the structure of their digestive organs. Accordingly, a 12-week trial was executed to assess the effects of two commercial flakes and a mix of lyophilized natural food on the condition of co-reared neon tetras, Paracheirodon innesi (Characidae), and glowlight rasboras, Trigonostigma hengeli (Danionidae). The four feeding groups were as follows: (T)—Tetra flakes; (O)—Omega flakes; (TO)—Tetra + Omega; (TOL)—Tetra + Omega + Lyophilizate (twice a week). There were no differences in final body weight (FBW) between the feeding groups of either species, but in the case of neon tetras, FBW increased significantly from the initial value only for the T group. However, histological observations and measurements of digestive organs (livers, intestines) showed pronounced differences between the two species. The supplementation with natural food in group TOL caused lipoid hepatic degeneration only in the rasboras. The healthiest histological structure of livers and longest intestinal folds were found in group T of the tetras and group TO of the rasboras. Whole-mount staining for bone and cartilage did not reveal any significant deformities or differences in terms of bone mineralization. In conclusion, it was outlined that concurrent feeding of co-housed, anatomically diverse ornamental fish species is a highly ambiguous task, because the nutritional strategy applied for a community tank may yield radically divergent effects, most of which may remain unnoticed when depending only on external body observations and measurements. Most emphatically, this was highlighted in regard to the dietary supplementation with natural food—although no significant effects were observed in neon tetras, severe lipoid liver degeneration occurred in glowlight rasboras.

Socio-economic determinants of net-income in fish farming in Kainji Lake Basin, Nigeria onomic determinants of net-income in fish farming in Kainji Lake Basin, Nigeria

The study analyzed the socio-economic determinants of net-income in aquaculture of Kainji, Lake Basin, Nigeria. Specifically, the study examined the; fish farming systems; cost and returns, socio-economic determinants of net-farm income and challenges of fish farming in the area. The study adopted a two-stage sampling procedure to select 120 table-size fish farmers. Data were collected with questionnaires that were administered through face-to-face interview and analyzed using descriptive statistics, budgetary technique and multiple regression analysis. The results showed that 35.00 % of the fish farmers were within the age bracket of 31-40 years, 53.34 % were men, 91.67 % were married, 55.83 % had between 1-5 years of experience in fish farming and 75.83 % had tertiary educational qualification. Majority (92 %) of the fish farmers practiced the monoculture of catfish using earthen ponds system. The estimated total expenses were <strike>N</strike> 14,953,330.74 while the total revenue generated from 9 fish ponds, each stocked with an average of 3883.986 fingerlings in 2 cycles per year was <strike>N</strike> 20,188,142.00. The estimated net-farm income after tax was <strike>N</strike> 5,234,811.26 while the net profit margin and return on investment was 25.93 % and 35% respectively. Age, experience and household size were positive and significant (p<0.05) socio-economic factors that affected net-farm income while the challenges of fish farming were high cost of feed ( ̅x=3.24), poor pricing ( ̅x =3.11), poor access to capital ( ̅x=3.09) and persistent poaching/theft ( ̅x= 2.67). Based on the findings of the study, it is recommended that there should be an intensive research by the fish nutrition division of National Institute for Freshwater Fisheries Research (NIFFR) on the possible alternatives of crude protein source that could be a perfect substitute to Clupeids in fish feeds. Keywords: aquaculture, catfish, socio-economic, profitability, farmers

Lipoxygenase Enzymes, Oligosaccharides (Raffinose and Stachyose) and 11sA4 and A5 Globulins of Glycinin Present in Soybean Meal Are Not Drivers of Enteritis in Juvenile Atlantic Salmon (Salmo salar)

Soybean meal has been largely investigated and commercially used in fish nutrition. However, its inclusion levels have been carefully considered due to the presence of antinutritional factors, which depending on a series of factors might induce gut inflammation damaging the mucosal integrity and causing enteritis. Several strategies including genetic engineering have been applied attempting to reduce or eliminate some of the antinutritional factors. Accordingly, we assessed the intestinal health of juvenile Atlantic salmon fed high levels of speciality soybean genotypes with reduced-to-no content amounts of lipoxygenases, altered glycinin profile and reduced levels of oligosaccharides. No major signs of enteritis, only indication of enteritis progression, was noticed in the soybean meal-based diets illustrated by mild changes in distal intestine morphology. Whereas fish, fed fishmeal control feeds, displayed normal distal intestine integrity. Speciality soybean types did not improve intestinal health of juvenile Atlantic salmon suggesting these antinutrients are not drivers of the intestinal inflammatory process in this species. No additional benefits in terms of production performance or blood biochemistry were noticed in the speciality soybean types compared to the traditional soybean.

Organic Selenium (OH-MetSe) Effect on Whole Body Fatty Acids and Mx Gene Expression against Viral Infection in Gilthead Seabream (Sparus aurata) Juveniles

The supplementation of fish diets with OH-SeMet reduces oxidative stress and modulates immune response against bacterial infection. However, despite the importance of essential polyunsaturated fatty acids in fish nutrition and their high risk of oxidation, the potential protective effect of OH-SeMet on these essential fatty acids has not been studied in detail. Moreover, while viral infection is very relevant in seabream production, no studies have focused the Se effects against viral infection. The aim of the present study was to assess the impact of dietary supplementation with OH-SeMet on gilthead seabream fatty acid profiles, growth performance and response against viral infection. Gilthead seabream juveniles (21.73 ± 0.27 g) were fed for 91 days with three experimental diets, a control diet without supplementation of Se (0.29 mg Se kg diet−1) and two diets supplemented with OH-SeMet (0.52 and 0.79 mg Se kg diet−1). A crowding stress test was performed at week 7 and an anti-viral response challenge were conducted at the end of the feeding trial. Selenium, proximate and fatty acid composition of diets and body tissues were analyzed. Although fish growth was not affected, elevation in dietary Se proportionally raised Se content in body tissues, increased lipid content in the whole body and promoted retention and synthesis of n-3 polyunsaturated fatty acids. Specifically, a net production of DHA was observed in those fish fed diets with a higher Se content. Additionally, both monounsaturated and saturated fatty acids were significantly reduced by the increase in dietary Se. Despite the elevation of dietary Se to 0.79 mg kg−1 not affecting basal cortisol levels, 2 h post-stress plasma cortisol levels were markedly increased. Finally, at 24 h post-stimulation, dietary OH-SeMet supplementation significantly increased the expression of the antiviral response myxovirus protein gene, showing, for the first time in gilthead seabream, the importance of dietary Se levels on antiviral defense.

Characterisation of Extracellular Enzyme-Producing Microorganisms From the Gut of Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758)

The current priority in the aquaculture industry is to replace fish meal with cheaper but efficient protein sources like plant-based feedstuffs to support global expansion and sustainability. Hence, research has focused on finding novel ways to increase the digestibility of plant-based diets. Exogenous enzymes have emerged as an excellent alternative to improve nutrient digestibility of the diet in animals, including fish. The present study aims to explore exogenous enzyme-producing bacteria in the gastrointestinal (GI) tract of Nile tilapia (Oreochromis niloticus (Linnaeus, 1758)). Two Gram-negative enzyme-producing (amylase, xylanase, and lipase) bacterial strains viz. Aeromonas veronii ONKP1 (GenBank accession no. MN602971) and Stenotrophomonas maltophilia ONKP2 (GenBank accession no. MN602972) were identified by biochemical tests and 16s RNA analysis. They are capable of utilising citrate, maltose, glucose, and gelatine. Besides, A. veronii ONKP1 can utilise mannitol, sucrose, and lactose, whereas S. maltophilia ONKP2 is catalase and urease positive. Aeromonas veronii ONKP1 was superior in terms of enzyme production to S. maltophilia ONKP2. Stenotrophomonas maltophilia ONKP2 is a rarely reported strain, specifically from healthy fish. Amylase, xylanase, and lipase could be used as feed additives for fermenting plant products and producing prebiotics like xylooligosaccharides. Further, this study might help understand the role of gut-associated bacteria viz. A. veronii and S. maltophilia, in fish nutrition.