Partial replacement of soybean meal by yellow mealworm (Tenebrio molitor) meal influences the flesh quality of Nile tilapia (Oreochromis niloticus)

Yellow mealworm (Tenebrio molitor) meal in diets of grass carp (Ctenopharyngodon idellus): Effects on growth performance, antioxidant capacity, immunity, intestinal morphology, and intestinal microbiota

The impacts of substituting dietary soybean meal (SBM) with yellow mealworm meal (YMM) were investigated during a 56-day feeding trial on growth, antioxidant capacity, immunity, intestinal morphology, and intestinal microbiota of grass carp. A total of 750 grass carp were divided into 5 groups (3 replications per group and 50 fish per replication) with different levels of YMM: SBM (control group), H25, H50, H75, and H100, for 8 weeks. The results showed that dietary YMM significantly increased final body weight (FW), weight gain (WG), and protein efficiency ratio (PER) in H25 group (P < 0.05); however, complete substitution showed the opposite trend (P < 0.05 for FW and WG). The liver antioxidant capacity was improved, manifested by enhanced superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities, glutathione (GSH) content and up-regulated antioxidant-related genes mediated by the Keap1-Nrf2 signaling pathway in the H25 group (P < 0.05). However, in the H100 group oxidative stress occurred in parallel with impairment of hepatic function. Intestinal inflammation was aggravated in the H100 group as evidenced by the up-regulated pro-inflammatory gene expression mediated by the NF-κB pathway (P < 0.05). Additionally, the activity of intestinal digestive enzymes for the grass carp was significantly reduced and accompanied with intestinal mucosal barrier dysfunction in the H100 group (P < 0.05). In summary, replacement of SBM with 25% YMM showed positive influences on growth, antioxidant capacity, immunity, and intestinal health. Conversely, complete replacement of SBM with YMM triggered oxidative stress, caused liver function disorder, and impaired intestinal health in grass carp.

Combined Effects of Yellow Mealworm (Tenebrio molitor) and Saccharomyces cerevisiae on the Growth Performance, Feed Utilization Intestinal Health, and Blood Biomarkers of Nile Tilapia (Oreochromis niloticus) Fed Fish Meal-Free Diets

Aquafeed quality is the most critical factor for aquaculture sustainability. However, limitations of traditional feed ingredients such as fishmeal (FM) need alternative strategies to ensure the nutritional requirements for aquatic animals. In this trial, four test diets were formulated (2 × 2 factorial design), where FM was incorporated in two diets at 10% with or without Saccharomyces cerevisiae (SC) at 1 g/kg. At the same time, FM was replaced with yellow mealworm (Tenebrio molitor) meal (TM) with or without SC at 1 g/kg. The growth performance indices (final weight, weight gain, and SGR), and the feed utilization indices (FCR and PER) were markedly affected by the protein source (FM or TM) and dietary SC (P < 0.05). The protein source (FM or TM) significantly (P < 0.05) affected the whole-body protein and lipid contents, while the moisture and ash contents were unaffected (P > 0.05) by TM or SC. The growth of the intestinal villi showed a marked increase in both height and branching in the treated groups with SC along the whole length of the intestine. Furthermore, the immune cell infiltration was prominent near the intestinal crypts of the middle intestinal segments in the supplemented groups by SC. Dietary TM and SC revealed improved hepatic parenchyma in the liver tissue better than other groups. The hematological indices, including hemoglobulin, hematocrit, red blood cells, and white blood cells, were markedly affected by dietary SC (P < 0.05). The lysozyme activity and phagocytic index were markedly affected by dietary SC, while phagocytic activity was affected by dietary TM (P < 0.05). The catalase, glutathione peroxidase, and malondialdehyde were markedly affected by the interaction between dietary protein source and SC, while superoxide dismutase was affected by dietary SC (P < 0.05). In conclusion, adding SC could enhance the utilization of TM by Nile tilapia with positive effects on the intestinal and liver histological features and the immune and antioxidative responses.

The defatted black soldier fly meal (Hermetia illucens) improved the pathogen resistance and gut health of Nile Tilapia (Oreochromis niloticus)

As a novel protein source, the black soldier fly (Hermetia illucens) possesses the potential to enhance fish health due to its high protein content, essential amino acids, and bioactive compounds, but the mechanisms by which defatted black soldier fly meal affects fish health remain unclear. This study aimed to evaluate the effects of partially replacing soybean meal (SM) with defatted black soldier fly larvae meal on the pathogen resistance of juvenile Nile tilapia (Oreochromis niloticus) and to explore the underlying mechanisms. Defatted black soldier fly (Hermetia illucens) meal was used to replace 0 % (CON), 15 % (H15), 30 % (H30), 45 % (H45), and 60 % (H60) of soybean meal in the diets, which were fed to Nile tilapia for 8 weeks. At the second week of the experiment, an unexpected infection was observed in the Nile tilapia, with subsequent isolation and identification confirming the pathogen as Aeromonas veronii. The results showed that defatted black soldier fly meal improved the survival rate and reduced the intestinal inflammation of Nile tilapia in H60 group compared to CON group (P < 0.05). Periodic acid-Schiff (PAS) staining of the gut indicated that a 60 % replacement of soybean meal with defatted black soldier fly meal significantly increased the number of goblet cells in the intestine (P < 0.05) and upregulated the expression level of mucin 2 (muc2) (P < 0.05). Throughout the experiment period, the survival rate in the defatted black soldier fly meal groups was higher than that in the soybean meal group, with the H60 group exhibiting the most significant improvement. In addition, defatted black soldier fly meal exhibited a promotion effect on goblet cell numbers, mucin production and mucin secretion with a dose dependent manner (P < 0.05). To identify the possible mechanism by which defatted black soldier fly meal enhanced goblet cell numbers, gut microbiome and metabolomics were conducted. The results showed that the defatted black soldier fly meal altered the composition of intestinal microbiota and increased the content of L-tyrosine in the H60 group. The effects of L-tyrosine were further identified in LS174T cells, and the results showed that L-tyrosine upregulated the expression levels of muc2 and SAM pointed domain-containing Ets transcription factor (spdef) (P < 0.05). In conclusion, the defatted black soldier fly meal improves gut health and enhances pathogen resistance, ultimately leading to the increased survival rates of Nile tilapia when exposed to A. veronii.

J. A, Sethupathy A. M, S. S, Alrashdi YBA, Ibrahim AE, El Deeb S. Current Status and Global Research Trend Patterns of Insect Meal in Aquaculture From Scientometric Perspective: (2013-2022)

In the past decade, insect meal has gained popularity in the animal feed industry, particularly in aquafeed, due to rising costs and decreased availability of fish meal (FM) and fish oil. Initially met with skepticism, insect meal is now seen as a promising ingredient because of its high nutrient profile. Research worldwide is exploring its potential as a FM replacement. Insects are abundant, nutritious, and environmentally friendly, as they can be reared on organic waste, minimizing the need for land, water, and energy. This research aims at obtaining a comprehensive and in-depth understanding of the current status and research trend patterns in this research field. To achieve this goal, this study conducts a mini systematic review and scientometric analysis of the global research published from 2013 to 2022 on the usage of insect meal in aquaculture. In the scientometric analysis, a total of 354 papers published by 1800 authors in 124 different journals from the Web of Science (WoS) core collection were analyzed, evaluating the number of publications, most relevant authors, organizations, top cited countries, most globally cited publications, and trending research themes in this field. The result showed that the University of Turin was the leading organization in insect meal research, whereas aquaculture was the leading journal, and author Laura Gasco was the prominent researcher in this field in the studied time frame (2013-2022). Italy was the leading country in Europe, while China dominated Asia in terms of the number of publications. The annual growth rate in insect meal research was found to be positive (23.11%), with 36.95 average citations per document. This study helps practitioners and scholars understand the current state of insect meal in aquaculture and identifies research requirements that can benefit both academia and industry.

Improving Yellow Mealworm (Tenebrio molitor) Utilization with Sodium Butyrate in Nile Tilapia Diets: Effects on Growth Performance, Intestinal Histology, Antioxidative Response, and Blood Biomarkers

Yellow mealworm (Tenebrio molitor) meal was introduced to aquafeed as a suitable protein source to replace fish meal (FM) and soybean meal and, thereby, consistent aquaculture production. However, mealworms should be added at adequate levels due to the presence of antinutritional factors such as chitin. Consequently, sodium butyrate (SB) is suggested to improve feed quality and ensure aquatic animals' productivity and welfare. In this study, parallel with the protein source (T. molitor meal or FM), dietary supplementation of SB (1 g/kg) is involved as a factor in the 2 × 2 factorial study. The first and the second diets were formulated using FM as a protein source with or without SB, while the third and fourth diets were prepared by replacing FM with T. molitor meal with or without SB supplementation. After 60 days, fish fed with FM or T. molitor and SB showed improved final body weight and weight gain, while those fed with T. molitor without SB had a reduced protein efficiency ratio. Histological analysis revealed that dietary SB improved intestinal histological features by increasing the height and branching of intestinal villi and immune cell infiltration near intestinal crypts in Nile tilapia-fed FM or T. molitor. Furthermore, fish-fed FM or T. molitor and SB had higher Hb, red blood cells, PCV, total protein, and globulin levels than fish-fed respective test diets without SB supplementation. Dietary SB addition to FM or T. molitor-based diets also significantly enhanced blood lysozyme and phagocytic activities, catalase, superoxide dismutase, glutathione peroxidase, and reduced MDA levels. Our results demonstrate that T. molitor meal can replace FM without compromising Nile tilapia's growth performance and health status. Additionally, SB supplementation improved T. molitor meal utilization by Nile tilapia, thereby significantly enhancing the growth, digestion capacity, intestinal histological features, and antioxidative and immune responses. Consequently, dietary T. molitor meal reduces the reliance on FM and improves the sustainability and efficiency of Nile tilapia production.

Effects of Five Lipid Sources on Growth, Hematological Parameters, Immunity and Muscle Quality in Juvenile Largemouth Bass (Micropterus salmoides)

This study investigated the effects of fish oil (FO), soybean oil (SO), rapeseed oil (RO), peanut oil (PO) and lard oil (LO) on growth, immunity and muscle quality in juvenile largemouth bass. After 8 weeks, the results showed that FO and RO could increase weight gain and serum alkaline phosphatase and apelin values compared with LO (p < 0.05). Except lower crude lipid contents, higher amounts of n-3 polyunsaturated fatty acids (15.83% and 14.64%) were present in the dorsal muscle of the FO and RO groups. Meanwhile, FO and RO could heighten mRNA levels of immune defense molecules (lysozyme, hepcidin, and transforming growth factor β1) compared with PO (p < 0.05). While SO could increase potential inflammatory risk via rising counts of white blood cells, platelets, neutrophils and monocytes, and mRNA levels of interleukins (IL-1β, IL-8, IL-12 and IL-15), FO and RO could improve hardness, chewiness and springiness through increasing amounts of hydroxyproline, collagen and lysyl oxidase, and mRNA levels of collagen 1α2 and prolyl hydroxylase in the fish dorsal muscle. Moreover, FO and RO could improve firmness through increasing glycogen and glycogen synthase 1 levels when compared with LO (p < 0.05). Therefore, these results could provide dietary lipid source references during the feeding process of adult largemouth bass.

Improving the nutritional values of yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) larvae as an animal feed ingredient: a review

Yellow mealworm larvae (YML; Tenebrio molitor) are considered as a valuable insect species for animal feed due to their high nutritional values and ability to grow under different substrates and rearing conditions. Advances in the understanding of entomophagy and animal nutrition over the past decades have propelled research areas toward testing multiple aspects of YML to exploit them better as animal feed sources. This review aims to summarize various approaches that could be exploited to maximize the nutritional values of YML as an animal feed ingredient. In addition, YML has the potential to be used as an antimicrobial or bioactive agent to improve animal health and immune function in production animals. The dynamics of the nutritional profile of YML can be influenced by multiple factors and should be taken into account when attempting to optimize the nutrient contents of YML as an animal feed ingredient. Specifically, the use of novel land-based and aquatic feeding resources, probiotics, and the exploitation of larval gut microbiomes as novel strategies can assist to maximize the nutritional potential of YML. Selection of relevant feed supplies, optimization of ambient conditions, the introduction of novel genetic selection procedures, and implementation of effective post-harvest processing may be required in the future to commercialize mealworm production. Furthermore, the use of appropriate agricultural practices and technological improvements within the mealworm production sector should be aimed at achieving both economic and environmental sustainability. The issues highlighted in this review could pave the way for future approaches to improve the nutritional value of YML.