Growth Performance Of Larvae Research Articles

Co-treatment of agri-food waste streams using black soldier fly larvae (Hermetia illucens L.): A sustainable solution for rural waste management

The management of rural waste, particularly agri-food waste, poses a major challenge to the ecosystem health. This study investigated the efficacy of black soldier fly larvae (Hermetia illucens L., BSFL) bioconversion for agri-food waste under independent treatment or co-treatment strategies using chicken manure and food waste as a model system. The results showed a synergistic effect of co-treating agri-food waste from different sources. The co-treatment strategy enhanced bioconversion efficiency, resulting in a 1.31-fold waste reduction rate and a 1.93-fold bioconversion rate. Additionally, larval growth performance and biomass quality of BSFL were improved, while lauric acid and oleic acid were enriched in the larval fat from the co-treatment strategy. 16S rRNA amplicon sequencing revealed that the co-treatment strategy reshaped both the residue and larval gut microbiota, with distinct enrichment of taxonomical biomarkers. Furthermore, under this strategy, metabolic functions of the residue microbiota were significantly activated, especially carbohydrate, amino acid, and lipid metabolism were enhanced by 16.3%, 23.5%, and 20.2%, respectively. The early colonization of lactic acid bacteria (Weisella and Aerococcus) in the residue, coupled with a symbiotic relationship between Enterococcus in the larval gut and the host, likely promoted organic matter degradation and larval growth performance. Scaling up the findings to a national level in China suggests that the co-treatment strategy can increase waste reduction quantity by 86,329 tonnes annually and produce more larval protein and fat with a market value of approximately US$237 million. Therefore, co-treatment of agri-food waste streams using BSFL presents a sustainable solution for rural waste management that potentially contributes to the achievement of SDG2 (Zero Hunger), SDG3 (Good Health and Well-Being), and SDG12 (Responsible Consumption and Production).

Organic Manure as Rearing Substrates for Red Worms (<i>Eisenia fetida</i>): Effects on Chemical Composition and Growth Performance

Red worms (<i>Eisenia fetida</i>) can convert biowaste and by-products into body mass and become high in protein and lipid content. However, the type of growth media used affects both larval body composition and growth performance. Using recycled organic materials from chicken manure (CM), cow dung manure (CDM) and rabbit manure (RM), the present study evaluated the production of red worms that could be used as a substitute protein source for fish meals. Two experiments were conducted, the first experiment tested the compatibility of each organic manure when mixed with soil separately, whereas the second experiment combined the three organic manures with a fixed amount of soil. The study was conducted for 60 days. The findings showed that red worms reared on 100 % CM had a significantly higher body weight (19.27 ± 0.9 g) followed by those reared on 100 % CDM and 75% RM, whereas red worms reared on 100 % RM had the lowest body weight (4.9 ± 0.1 g). A combination of 20% CM + 40% CDM + 20% RM + 20% Soil supported significantly higher body weight of red worms (24.9 ± 1.1 g), while the lowest value of body weight (5.1 ± 0.2 g) was in a combination of 20% CM + 0% CDM + 60% RM + 20% Soil). Furthermore, the results revealed that red worms reared on 100 % CDM without soil as waste substrate had the highest crude protein (73.28% DM) compared to red worms reared on other types of substrates. The study suggests the potential of reusing organic manure such as chicken and cow dung manure at different inclusion levels in the production of red worms.

Optimizing Goldfish (Carassius auratus) Breeding and Larval Nurturing for Materialistic Aquaculture Utilizing Synthetic Hormones

Gold fish (Carassius auratus) are familiar in India as an ornamental freshwater fish with economic importance. This experiment aimed to explore the possibility for mass-scale breeding and larval rearing of goldfish under biofloc setup. Natural brooders were collected, acclimatized and induced to breed utilizing synthetic hormones at various dosages. Breeding execution parameters namely spawning success, fertilization rate and hatching performance were analysed. The highest fertilization and hatching rate were gradually noticed at 80.8% and 80.9% by using a dose of 0.4ml/kg body weight for females and 0.2ml/kg for males. Larval rearing was accomplish by applying several live and formulated feeds across various life stages in normal rearing tanks and biofloc tanks also. The growth performance of larvae in biofloc tanks express a satisfactory rate, with a maximum weight gain of 7.1 g and length gain of 5 cm over 120 days compared to 5.1 g and 3.5 cm in normal tanks. Water quality parameters were kept within the optimum range all over the experiment. The functionable study exhibits the viability of captive breeding and mass scale larval nurturing of goldfish employing induced breeding techniques and biofloc technology.

Growth performance, proximate composition and fatty acid profile of black soldier fly larvae reared on two grape pomace varieties

The black soldier fly (Hermetia illucens) is attracting increasing interest for its ability to convert low-value substrates into highly nutritious feed. This study aimed at evaluating grape pomace from two varieties (Becuet – B; Moscato – M) as rearing substrates for black soldier fly larvae (BSFL), focusing on the related effects on larval growth performance, proximate composition, and fatty acid profile. A total of six replicates per treatment, and 1 000 BSFL per replica, were used. Larval development was assessed by larvae weight, which was recorded eight times during the trial: the day after the beginning of the trial, and then on days 5, 8, 13, 15, 20, 22, and 27 (day in which the 30% of BSFL reached the prepupal stage). Production and waste reduction efficiency parameters, namely the growth rate, substrate reduction and substrate reduction index, were calculated. The two grape pomace varieties were analysed for their proximate composition and fatty acid profile; the same analyses were conducted on BSFL (30 larvae per replica) that were collected at the end of the trial (day 27). The growth rate of BSFL showed a higher value when the larvae were reared on B substrate (4.4 and 3.2 mg/day for B and M, respectively; P < 0.01). The rearing substrate did not significantly affect the proximate composition of BSFL. The percentage of total lipids (TL) in M-fed BSFL was significantly higher than in B ones. Total saturated (P < 0.001) and monounsaturated fatty acids (P < 0.05) were significantly higher in M-fed BSFL, while an opposite trend was observed for total branched-chain (P < 0.001) and total polyunsaturated fatty acids (P < 0.001). Interestingly, some conjugated linoleic acid (CLA) isomers [i.e., C18:2 c9t11(+t7c9+t8c10) and t9t11] were detected in low amounts in both rearing substrates (total CLA equal to 0.085 and 0.16 g/100 g TL in B and M substrate, respectively). Some CLA isomers (i.e., C18:2 c9t11, t7c9, and t10c12) were also found in BSFL, reaching a total CLA concentration equal to 2.95 and 0.052 g/100 g of TL in B-fed and M-fed BSFL, respectively. This study demonstrates that winery by-products from different grape varieties can significantly affect the development and lipid composition of BSFL. The CLA biosynthesis potential of BSFL opens newsworthy perspectives for a new valorisation of winery by-products to produce full-fat black soldier fly meal and black soldier fly oil enriched in specific fatty acids of potential health-promoting interest.

Optimizing substrate moisture content for enhanced larval survival and growth performance in Hermetia illucens: exploring novel approaches

Insects are receiving a lot of attention as an alternative protein source, especially the black soldier fly, Hermetia illucens. This insect is of particular interest due to its potential as a waste converter as it can be grown on low-value organic substrates, such as agricultural side-streams, manure and decomposing materials. It’s capacity to turn low-value biomass into high-quality protein provide new opportunities in organic waste management. Unfortunately, rearing of black soldier fly larvae (BSFL) does not run efficiently on most substrates. Several parameters influence the rearing efficiency of BSFL. One of the parameters that is often overlooked is the moisture content of the substrate and the physical properties, such as water release/holding, associated with it. In this study the water release properties of 3 BSFL feeds, each at a dry matter content ranging from 10 to 90%, were investigated using 4 different methods, being water release by (1) filtration, (2) sedimentation, (3) syneresis and (4) centrifugation. Rearing of BSFL on the substrates with different dry matter content showed that water release influences larval performance and survival. Moreover, correlating survival to water release indicated that when substrates are hydrated to the minimum dry matter content, at which no water release is measured by the sedimentation method, the highest BSFL survival can be achieved for that substrate. In addition, a standardised method for determining the most optimal dry matter content of substrates based on substrate water holding capacity was developed.

First feeding of a marine ornamental fish, the White‐barred Goby Amblygobius phalaena: Investigating the optimal initial live feed organisms and optimal feeding density

AbstractObjectiveThe White‐barred Goby Amblygobius phalaena is a popular ornamental fish in the marine aquarium market. To achieve successful commercial production, efficient larval rearing techniques are crucial. Previous studies have achieved successful cultivation of White‐barred Goby larvae by using a combination of three live feed organisms—the ciliate Euplotes sp., the rotifer Brachionus rotundiformis, and the copepod Apocyclops royi nauplii—during the first feeding stage. However, the specific contributions of these live feed organisms to larval survival and growth remain unclear. Moreover, the optimal feeding density for the critical initial live feed organism has not been determined experimentally. In this study, we aimed to enhance the larviculture protocol for White‐barred Goby by introducing Portuguese oyster Crassostrea angulata trochophores and by addressing these knowledge gaps.MethodsLarvae were initially cultured through individual and combined feeding with four live feed organisms: Euplotes sp., Portuguese oyster trochophores, B. rotundiformis, and A. royi nauplii. The objective was to identify the optimal initial live feed organism during the first feeding stage by assessing the survival and growth performance of larvae. Subsequently, using this optimal live feed organism, larvae were cultured at four feeding densities (2, 5, 10, and 20 individuals/mL). Through evaluating feeding incidence, feeding intensity, survival, and growth performance, the aim was to determine the optimal feeding density for the selected live prey.ResultOur experiments revealed that White‐barred Goby larvae could consume both oyster trochophores and Euplotes sp. during the first feeding stage. However, larvae exhibited superior survival and growth performance when fed oyster trochophores. The optimal feeding density of oyster trochophores was determined to be 10 individuals/mL, while a feeding density as high as 20 individuals/mL resulted in decreased larval feeding incidence.ConclusionThese findings have significant implications for enhancing larval production programs for marine ornamental gobies and promoting their sustainable commercialization.

The Use of probiotics in fermenting food wastes for production of black soldier fly larvae (Hermetia illucens L.; Diptera: Stratiomyidae)

Larvae of the black soldier fly (BSF) can process a wide variety of organic wastes and convert them into larval body primarily consisting of protein. Production of larvae with high-quality protein content is affected the rearing system, one of them is quality of feeding substrates. This study was aimed to evaluate the effect of food wastes fermented by probiotic culture as the feeding substrates for producing the BSF larvae. The probiotic cultures used were Lactiplantibacillus plantarum E2 and Limosilactobacillus fermentum F5, while the food wastes were derived from a seafood restautrant. Four rearing substrates were compared: food wastes fermented by Lactiplantibacillus plantarum E2 (P1), food wastes fermented by Limosilactobacillus fermentum F5 (P2), food wastes fermented by consortium (Lactiplantibacillus plantarum E2 + Limosilactobacillus fermentum F5) (P3), and food wastes without probiotics (P0). Before the feeding substrates were applied, the food wastes were fermented by the probiotics for 10 days. Six-day-old BSF larvae were reared for 14 days on each fermented substrate. The larval growth performance observed were fresh weight, length and width, while the nutrient content of the larvae was protein and fat content. The waste reduction index was also measured. The data showed that the best larval growth performance was shown in P3 substrate, with fresh weight of 287.27 g, larva length and width of 19.93 mm and 3.53 mm, respectively. In P3 substrate also could produce the larvae with the best nutrient content, with protein and fat content by 12.53% and 16.09%, respectively. The waste reduction index value of P3 substrate was 6.12%. The duration of BSF larvae rearing required to be extended to obtain an increased average protein content. This finding of this study could be helpful for improving the quality of BSF larvae by applying consortium of probiotic cultures in fermenting the feeding substrates.

Future Proteins: Sustainable Diets for Tenebrio molitor Rearing Composed of Food By-Products.

Since the human population is continuously growing, sufficient food with low environmental impact is required. Especially, the challenge of providing proteins will deepen and insects can contribute to a more sustainable and efficient source of protein for human consumption. Tenebrio molitor larvae are highly nutritious and rearing mealworms is more environmentally friendly compared to the production of traditional livestock meat. To use T. molitor as a more sustainable alternative to conventional proteins, it is essential to apply diets from a local and sustainable source. Therefore, the objective of this study was to find local by-products or leftovers which can be used in mass production of larvae as a main substrate. Feeding trials investigating twenty-nine different substrates were conducted to evaluate larval growth performance and adult reproduction by determining development times, survival rates, biomass, and fecundity. Several suitable by-products were identified that can be used in high quantities as single component diet for T. molitor rearing, revealing a high survival rate, short development time, high mean total biomass, and successful breeding. The most successful substrate-malt residual pellets-was found to be an alternative to the most used substrate, wheat bran. Furthermore, corn germ meal, sweet chestnuts, bread remains, soybeans, sweet potatoes, and wheat germs have been discovered to be suitable diets for T. molitor. Moreover, the findings of this study contribute towards using several substrates as supplements.

Differentially Charged Nanoplastics Induce Distinct Effects on the Growth and Gut of Benthic Insects (Chironomus kiinensis) via Charge-Specific Accumulation and Perturbation of the Gut Microbiota.

Nanoplastics (NPs), as an emerging contaminant, have usually been found charged in the environment, posing threats to aquatic animals. However, the underlying mechanisms governing the gut toxicity of differentially charged NPs to benthic insects are not well understood. In this study, the gut toxicity in larvae of Chironomus kiinensis exposed to negatively charged NPs (PS-COOH, 50 nm) and positively charged NPs (PS-NH2, 50 nm) at 0.1 and 1 g/kg was investigated through fluorescence imaging, histopathology, biochemical approaches, and 16S rRNA sequencing. The results showed that PS-NH2 caused more adverse effect on the larval growth performance and induced more severe oxidative stress, epithelial damage, and inflammatory responses in the gut than PS-COOH. The stronger impact caused by PS-NH2 was because the gut accumulated PS-NH2 more readily than PS-COOH for its negatively charged cell membrane. In addition, PS-NH2 were less agglomerated compared with PS-COOH, leading to an increased interaction with gut cell membranes and microbiota. Furthermore, alpha diversity and relative abundance of the keystone microbiota related to gut barrier and nutrient absorption were markedly lower exposed to PS-NH2 than PS-COOH, indirectly exacerbating stronger gut and growth damage. This study provides novel insights into the effect mechanisms underlying differentially charged NPs on benthic insects.

The effect of dietary docosahexaenoic acid (DHA; 22:6n-3) on photoreceptor abundance, rhodopsin expression and growth in developing gilthead sea bream (Sparus aurata) larvae

This study determined the effect of prey DHA on larval gilthead sea bream (GSB; Sparus aurata) photoreceptor abundance, rhodopsin expression, and growth performance. It was carried out in a twenty-eight 400 l conical tank system that was stocked with 100 viable GSB eggs/l/tank. This allowed the testing of 4 levels of rotifer DHA; 0.99 (Low; L), 1.9 (Intermediate low; I-L), 3.2 (Intermediate high; I-H) and 12.1(High; H) mg DHA/g DW rotifer, which were fed (10 rotifers/ml) to 3-16 DPH larvae. These rotifer diets continued to be offered to 17-34 DPH fish, although these larvae predominantly fed on 4 DHA enriched Artemia nauplii treatments that were offered at a concentration from 0.1 nauplii/ml to 4 nauplii/ml, depending on larval age. This resulted in 4 DHA rotifer-Artemia ranges: 0.99-0.0 (L), 1.9-2.6 (I-L), 3.2-7.2 (I-H), and 12.1-11.77 (H) mg DHA/g DW. The 4 DHA treatments and ranges were tested in replicates of 7 conical tanks per treatment. Increasing rotifer DHA significantly (P&lt;0.0001) improved TL, in an exponential manner, throughout larval rearing. DW in 34 DPH larvae was markedly (P&lt;0.05) enhanced with dietary DHA inclusion in the rotifers and Artemia. There was a significant (P &lt; 0.005) prey DHA dose dependent range effect on the abundance of photoreceptor cells in the retina of 34 DPH larvae. The gene expression of rhodopsin in GSB larvae was significantly (P&lt;0.05) upregulated with dietary DHA dose range and larval age (P&lt;0.0001). This study established a link between dietary DHA level with photoreceptor abundance and rhodopsin expression, which led to improved vision, prey acquisition, and growth in developing GSB larvae.

Process performance evaluation of faecal matter treatment via black soldier fly

Abstract Sustainable management of faecal matter is a prevailing global challenge. In this study, we assessed black soldier fly (BSF) process performance during co-treatment of faecal matter using kitchen waste (FM:KW) to formulate five feeding substrates. About 1 kg of each feed substrate was treated utilizing 5 g of 5-day-old BSF larvae after which 100 larvae were randomly picked at 3-day intervals from each treatment to monitor the larval weight gain across the treatment process. Larval days to 50% pupation, mean pupal yield, waste reduction rate (WR), bioconversion rates (BRs), and feed conversion rates (FCRs) were monitored for the process performance. Study results showed that the substrate 1:1 attained the best measures of high WR, waste reduction index (WRI), BR, FCR, and overall pre-pupal yield within a shorter development time. Further, we modelled the BSF larval weight gain using the modified Gompertz model to assess the least time for optimal biomass conversion for animal feed processing. The BSF larvae exhibited an S-shaped growth curve and the modified Gompertz model adequately quantified the BSF larval growth performance. In the future, our methodology will pave the way for effective treatment and valorization of faecal matter from onsite sanitation facilities, manage organic municipal wastes and provide alternative animal feed and bio-fertilizer.

Effects of supplemental fulvic acid on survival, growth performance, digestive ability and immunity of large yellow croaker (Larimichthys crocea) larvae.

A 30-day feeding trial was designed to evaluate the effect of supplemental fulvic acid (FA) on survival, growth performance, digestive ability and immunity of large yellow croaker (Larimichthys crocea) larvae (initial body weight 11.33 ± 0.57mg). Four isonitrogenous and isolipids diets containing 0.00%, 0.01%, 0.02% and 0.04% FA were formulated, respectively. Results showed that the supplementation of 0.04% FA significantly improved survival rate of large yellow croaker larvae. Meanwhile, supplemental FA significantly increased final body weight and specific growth rate. Based on the specific growth rate, the optimal supplementation was 0.0135% FA. Larvae fed the diet with 0.01% FA had significantly higher villus height than the control. The supplementation of 0.01%-0.02% FA significantly increased the muscular thickness of intestine. Moreover, supplementation of FA significantly increased mRNA expression of intestinal epithelial proliferation and barrier genes (pcna, zo-1 and zo-2). Diets supplemented with 0.02%-0.04% FA significantly increased the activity of trypsin in the intestinal segment, while 0.01%-0.02% FA significantly increased the activity of trypsin in the pancreatic segment. Compared with the control, supplementation of FA remarkably increased activities of alkaline phosphatase and leucine aminopeptidase in the brush border membrane of intestine. Larvae fed the diet with 0.01% FA significantly increased activities of lysozyme and total nitric oxide synthase. Furthermore, the supplementation of 0.01% to 0.02% FA significantly decreased the mRNA expression of pro-inflammatory cytokines (tnf-α and il-6). Concurrently, supplemental FA significantly increased anti-inflammatory cytokine (il-10) mRNA expression level. In conclusion, this study indicated that the supplementation of FA could improve the survival rate and growth performance of larvae by promoting intestinal development, digestive enzymes activities and innate immunity.

Delayed First Feeding Chronically Impairs Larval Fish Growth Performance, Hepatic Lipid Metabolism, and Visceral Lipid Deposition at the Mouth-Opening Stage.

During the mouth-opening stage, fish larvae are susceptible to delayed first feeding (DFF). In this study, we explored the effects of DFF for two days on later growth and energy metabolism in larval fish. Results showed that DFF chronically impaired larval growth performance, thereby reducing the efficiency of feed utilization by larvae. In DFF larvae, the mRNA levels of growth inhibitors (i.e., igfbp1a and igfbp1b) were significantly upregulated and consistently maintained at high expression levels, which may be an important attribution of larval growth retardation. Concomitantly, DFF retarded the growth of adipose tissue and reduced lipid deposition in larval viscera, suggesting lipid metabolism is disordered in DFF larvae and generates inefficient lipid reserves. In the liver, we observed that DFF resulted in a significant accumulation of neutral lipids, and this phenotype did not disappear rapidly after DFF larvae received exogenous nutrition. As to the transcript analyses, we found that the expression of genes related to hepatic lipid synthesis (e.g., srebf1, srebf2, dgat1a, dgat1b, fasn, and scdb) in DFF larvae was consistently upregulated, while the expression of genes involved in lipid transport (e.g., apoa2, apoa4b.1, and apoa4b.3) was downregulated. Therefore, it appears that the inefficient lipid reserves in DFF larvae are associated with their hepatic lipid transport dysfunction. Taken together, our findings contribute to understanding the impairments to fish larvae caused by delayed first feeding during the mouth-opening stage and to aiding larval management in the aquaculture industry.

Path analysis of desirable traits and evaluation of reproductive performance of Crassostrea sikamea in different ages

Kumamoto oysters (Crassostrea sikamea) are important marine aquaculture shellfish because of their taste and round shell shape. Due to its small size, selective breeding is required to improve its market size, but there are no reports on traits suitable for direction selection and reproductive productivity of Kumamoto oysters of different ages. In this study, path analysis and one-way ANOVA were used to explore the influential indices of oyster body weight and fecundity. The results showed that shell height was the main factor affecting the body weight of Kumamoto oysters at one-year-old and two-year-old, followed by shell length. Body weight was the main factor influencing fecundity, and shell height showed a significant correlation with fecundity. Therefore, shell height should be considered the first parameter for selection when selecting Kumamoto oysters for body weight as the direct selection target. When one-year-old and two-year-old Kumamoto oysters were selected as parents from Xiangshan Bay, hatching parameters and growth parameters of F1 generation larvae were measured. The fecundity and egg diameters were 1.72 × 106 and 46.60 ± 3.62 μm, respectively, which were significantly greater than one-aged oysters (5.86 × 105, 40.26 ± 3.52 μm). The hatching parameters (fertilized egg size, fertilization rate, and hatching rate) and larval growth performance (D-stage veliger and veliger) were similar and did not differ significantly (P > 0.05), and after metamorphosis, there was also no significant difference in shell height size at 40 days of age (P > 0.05). Therefore, there was no significant effect of age on reproduction, larval development, and the early growth of Kumamoto oysters. These results could provide a basis for parental sources and proper traits for Kumamoto oyster selection, which is beneficial to developing and utilizing this excellent germplasm resource.

Evaluation of short and long term enrichment of Artemia franciscana with mixed algae or DHA oil emulsion for improving Dicentrarchus labrax larvae aquaculture

Setting up nutritional requirements with high-quality, time-saving marine finfish larvae is a big issue for increasing aquaculture profit. In the current study, we evaluated the nutritional value of two enrichment diets [DHA oil emulsion-enriched Artemia (Art-DHA-Selco) and mixed algae-enriched Artemia (Art-MA)] and two-timing protocol (2 & 24 h) for serving European Sea bass. Larval growth performance and survival percentage, as well as biochemical compositions of the enriched Artemia and for the fed larvae after 25 rearing days, were determined. The results revealed that survival percentage (S%), feed conversion ratio (FCR), and protein efficiency ratio (PER) was insignificantly affected by the two factors (diets and time) or the interaction between them. Otherwise, growth in terms of final body weight (FBW), specific growth rate (SGR) as well as productive protein value (PPV) differed significantly at (P ≤ 0.01) among treatments in both factors. Concerning biochemical analysis, the highest protein value was recorded in Art-MA at 24 h. In contrast, lipid and carbohydrate levels were considerably higher in Art-MA 2 h than in the Art-DHA. That decrease in protein content, FBW, and SGR in the 2 h period in the MA treatment may attribute to the smaller size of the Artemia metanauplii in the 2 h than those after 24 h. That can be overcome by starting with Artemia metanauplii at the end with Instar II before enrichment process so that the size is big enough to give better results. The results revealed that PUFAs percentages were significantly highest especially EPA percentage in the enriched Art-MA 2 h followed by its correspondence Art-MA at 24 h compared with Art-DHA or un-enriched ones. Otherwise, the fatty acid composition (FA) of post-larvae surpassed greatly in EPA and n3/n6 ratios as diet reflection in the algal short-term duration. Based on the results and the documented drawbacks of DHA-Selco, the authors recommended using mixed algae in the enrichment protocol for feeding larval stages over the short term.

Effect of pH on Egg Hatching, Larval Growth Performance, and Enzymatic Activity of the Nile tilapia Oreochromis niloticus

Effect of pH on Egg Hatching, Larval Growth Performance, and Enzymatic Activity of the Nile tilapia Oreochromis niloticus

Biowaste and by-products as rearing substrates for black soldier fly (Hermetia illucens) larvae: Effects on larval body composition and performance.

Black soldier fly (Hermetia illucens) larvae can convert biowaste and by-products into body mass high in protein (~40% dry matter, DM) and lipid (~30% DM). However, the type of rearing substrate also affects the larval body composition and thus its nutritional value. Hitherto, it remains unclear how and to what extent the larval body composition can be altered by the substrate. This study was therefore performed to examine the possibilities of modifying larval body composition using different rearing substrates. To investigate this, 5-days old larvae were reared for seven days on different locally available waste and by-products: brewer’s spent grain, mitigation mussels (Mytilus edulis), rapeseed cake, and shrimp waste meal (Pandalus borealis). Larval composition and performance were compared to larvae reared on a commercial chicken feed as well as a mixed feed (mixture of chicken feed and by-products, with a similar macronutrient composition to chicken feed). Larval body weight was recorded daily to determine growth over time whereas larvae and substrates were sampled at the start and end of the trial and analysed for their nutritional composition. The type of rearing substrate affected both larval body composition and growth performance. There was a clear relation between the nutritional composition of the substrate and larvae for certain fatty acids. Larvae reared on marine-based waste substrates contained a higher share of omega-3 fatty acids than larvae reared on the other substrates, indicating an accumulation of omega-3 fatty acids from the substrate. There was a strong positive linear correlation between the ash content in the substrate and larvae whereas larval lipid, protein, amino acid, and chitin content seemed more affected by larval development. Overall, this study showed that the rearing substrate affects larval composition and development, and that larval composition of certain nutrients can be tailored depending on further food and feed applications.

Enrichment of livefeed with very low level of docosahexaenoic acid (DHA) is enough for yellowtail sea bream (Acanthopagrus latus) larvae

The marine fish larvae mostly rely on livefeed, with certain nutritional deficiencies such as poor long chain fatty acids, in spite of recent progress in developing artificial feed. Thus, the present experiment was conducted to evaluate a 30-day dietary effects of enriched rotifer (Brachionus rotundiformis) and Artemia nauplii (Artemia franciscana) with docosahexaenoic acid (DHA) on performance of yellowtail sea bream (Acanthopagrus latus) larvae. For this purpose, 60,000 larvae from wild broodstocks were stocked in 12 tanks (50 larvae/L) supplied with green water (0.5 ×106 cell/ml Nannochloropsis. sp). The rotifer and Artemia were enriched with four experimental emulsions contained four levels of DHA including very low (6 %, DHA-VL), low (12 %, DHA-L), medium (24 %, DHA-M) and high (37.8 %, DHA-H). Larvae were fed with rotifers from day 2–20 post hatch (DPH) and Artemia metanauplii (Instar-II, from 16 to 30 DPH). After the 30-day dietary trial, survival rate and growth performance of larvae were found not affected by different levels of DHA (P > 0.05). The activity of digestive enzymes including total proteases, lipase, amylase, alkaline phosphatase, and leucine-alanine peptidase showed some fluctuations among the experimental groups. However, in the most of the sampling intervals, except for protease activity, the activity of digestive enzymes did not change significantly among the experimental groups. The n–3 polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA) and DHA, were the highest in the whole body of larvae from DHA-M treatment. The DHA/EPA ratio in the whole body of larvae was significantly increased with increasing DHA level (P < 0.05). Based on our findings, very low levels of DHA is enough for supporting normal growth, survival and metamorphosis in developing A. latus larvae up to 30 days post hatching.

Improvement the Hatchery Seed Production Strategy on Embryonic Development and Larval Growth Performance and Development stages of Green Tiger Prawn, Penaeus semisulcatus Using Environmental Aspects

This investigation aimed to improve the hatchery seed production strategy in terms of chronologies of embryonic and larval development as well as hatching, growth and survival rates, and rearing water quality of green tiger prawn, Penaeus semisulcatus by the integration effects of different water temperatures (23 °C, 26 °C, 29 °C, 32 °C) and probiotic as water additives. The best and shortest chronologies of embryonic development stages were in favor of 32 °C with probiotic. The best hatching rate was in favor of 29 °C with probiotics. The fastest larval development and greatest larval growth as total length until PL1 stage was promoted by 32 °C with probiotic but the best survival rate was recorded at 26 °C with probiotic followed by 29 °C with probiotic treatment. During larval development, the lowest value of NH4–N was recorded under the effect of 26 °C and probiotic. Therefore, probiotics as water additives at 29 and 32 °C water temperatures have a beneficial impact on the hatchery seed production strategy and quality of P. semisulcatus. Our findings could apply to rearing larvae in shrimp hatchery to decrease the chronology of embryonic and larval development, while increase the hatching rate, growth performance, and survival rates as well as improving the water quality.

Enrichment and speciation changes of Cu and Cd in black soldier fly (Hermetia illucens) larval compost and their effects on larval growth performance

Municipal sludge (MS), rainwater sludge (RS), and kitchen waste (KW) were used as nutritional supplements for black soldier fly larvae (BSFL). Cd (52.3 %) was more easily assimilated in the BSFL body than Cu (34.8 %). After biotransformation in BSFL, the weak acid-soluble fraction (F1) of Cu and Cd increased by an average of 29.0 % and 42.7 %, respectively, whereas the reducible fraction (F2) of Cu and Cd decreased by an average of 13.8 % and 56.4 %, respectively, in the BSFL sand (BSFL feces and waste residues). A significant correlation (P < 0.01) was found between pH and the speciation of Cu and Cd. The abundance of Bacteroides had a positive correlation (P < 0.05) with the F1 of Cu, an extremely significant negative correlation (P < 0.001) with the F2 of Cd, and an extremely significant positive correlation with the F1 of Cd (P < 0.001). In addition, Cu and Cd exposures significantly (P < 0.01) reduced larval weight by 67.7 % and 45.3 %, respectively, pupation rate by 46.3 % and 26.5 %, respectively, and eclosion rate by 35.5 % and 33.4 %, respectively. Exposure to high concentrations of Cu and Cd also prolonged the development cycle (1–12 days) of BSFL and led to the failure of BSFL to complete their metamorphosis.