Juvenile Diet Research Articles

The effect of laboratory diet and feeding on growth parameters in juvenile zebrafish

Despite being one of the most used laboratory species in biomedical, behavioral and physiological research, the nutritional requirements of zebrafish (Danio rerio) are poorly understood, and no standardized laboratory diet exists. Diet and feeding regimen can substantially impact the welfare of the fish and, in turn, experimental reproducibility. Consequently, the establishment of a standardized diet and feeding protocol for laboratory zebrafish is imperative to enhance animal welfare, guarantee research reproducibility and advance the economic and environmental sustainability of laboratory dietary practices. Here the aim of this systematic review is to provide an overview of the parameters that need to be standardized in future nutritional studies to facilitate future meta-analyses for confirmation of an optimal juvenile diet for growth. A comprehensive search was conducted in PubMed and Scopus to identify relevant studies published up to August 2023, and the studies were selected on the basis of the predefined inclusion/exclusion criteria. The databases yielded a total of 1,065 articles, of which 14 were included in this review. We conducted data extraction and risk-of-bias analysis in the included studies. Statistical comparisons for specific growth rate, weight gain (%) and length gain (%) parameters were performed to determine the optimal feed for enhanced juvenile growth. We identified significant heterogeneity and caveats to our findings owing to a lack of standardization of experimental conditions in nutritional studies. Our findings highlight an urgent need for research on zebrafish nutrition. Therefore, the standardized parameters we have reported here represent a critical starting point for studies.

The life (history), diet and death of the blackspot shark (Carcharhinus sealei) from South-east Asia

Context The blackspot shark (Carcharhinus sealei) is a small-bodied coastal shark often incidentally caught in fisheries across South-east Asia. Aims This study aimed to document the species’ biology, ecology, fisheries and markets to inform conservation. Methods In total, 103 blackspot sharks from Indonesia (n = 101) and Singapore (n = 2) were examined to determine biological parameters (growth rate, age at maturity, reproductive traits and diet). An interview with a Singaporean seafood supplier gave insight to population trends, fisheries and markets. Key results Males attained a maximum age of 9 years, the smallest mature individual measured 709-mm stretched total length (STL), with 50% reaching maturity at 6.15 years. Females attained a maximum age of 11 years, the smallest mature individual measured 730 mm STL, with 50% reaching maturity at 6.12 years. The species has an overall growth rate (k) of 0.37 year−1. Reproduction was asynchronous, with only two pups produced per litter. Crustaceans dominated the diet of juveniles, whereas bony fishes and cephalopods dominated the diets of adult males and adult females respectively. Conclusions Blackspot sharks have a moderately fast growth rate, but a late age-at-maturity and a low fecundity. Diet differed between the sexes as well as adults and juveniles. Implications The low fecundity and late maturity of blackspot sharks increase their vulnerability to exploitation. Blackspot sharks are now listed on CITES-Appendix II, but mortality may remain high because they are reportedly often caught incidentally.

Assessing the Effects of Guiera senegalensis, Pluchea odorata, and Piliostigma reticulatum Leaf Powder Supplementation on Growth, Immune Response, Digestive Histology, and Survival of Nile Tilapia (Oreochromis niloticus Linnaeus, 1758) Juveniles before and after Aeromonas hydrophila Infection

The effects of three medicinal plants in the feeds of juvenile Nile tilapia (Oreochromis niloticus) were investigated on growth, survival, immunity, and digestive histology at various inclusion levels: (A) Guiera senegalensis at 0, 1, 2, 4, and 8%; (B) Pluchea odorata at 0, 0.5, 1, 2, and 4%; (C) Piliostigma reticulatum at 0, 1, and 2%; and (D) a mixture of the three at 0, 1, and 2%. After 28 days of feeding, fish were infected with Aeromonas hydrophila for 12 days. The results showed that, except for G. senegalensis, the inclusion of the medicinal plants, alone or combined, enhanced the immune response. The diet with 4% P. odorata significantly increased plasma lysozyme and bactericidal activities without affecting feed conversion efficiency or growth. Despite improved immunity, none of the treatments enhanced post-infection survival rates. However, fish fed the 1% mixture showed healthier livers and intestines, with reduced cell swelling and normal lipid deposits, followed by the 2% mixture and the control. These results highlight the potential benefits of incorporating P. odorata and the plant mixture into the diets of Nile tilapia juveniles for enhancing their immune response against A. hydrophila.

Optimization of dietary protein based on ideal protein concept for genetically improved farmed tilapia (GIFT) juveniles reared in inland saline water

A 60-day feeding trial was performed to optimize dietary protein based on the ideal protein concept for genetically improved farmed tilapia (GIFT) juveniles reared in inland saline water (ISW) of 10 ppt salinity. Seven heteronitrogenous (373.6–256.5 g crude protein/kg), isocaloric (∼ 16 MJ digestible energy/kg) and isolipidic (∼ 80 g lipid/kg) semi-purified feeds were formulated and prepared with decreasing levels of crude protein (CP), namely 373.6 (CP1), 352.2 (CP2), 334.5 (CP3), 314.9 (CP4), 293.7 (CP5), 275.2 (CP6) and 256.5 g/kg (CP7). The proportion of total essential and semi-essential amino acids was kept constant in all diets as ideal amino acid profiles and total non-essential amino acids were reduced linearly to reduce the dietary CP levels. Three hundred fifteen juveniles (average weight 4.76 ± 0.01 g) were randomly assigned into seven groups in triplicate. Fish of various groups were fed thrice daily at an apparent satiation level. The growth of juveniles increased linearly and quadratically (p<0.05) when the CP level of diets was decreased from 373.6 (CP1) to 334.5 g/kg (CP3), then declined linearly. The CP2 and CP3 groups had significantly higher feed intake and lower feed conversion ratio. In contrast, low CP-fed groups had superior protein utilization, viscerosomatic index and hepatosomatic index than other groups. The CP1 and CP2 groups had significantly higher whole-body protein and lower lipid content. The whole-body non-essential amino acid content diminished linearly (p<0.05) as dietary CP levels were decreased; the whole-body essential amino acid content remained unchanged (p>0.05). The high CP-fed juveniles (CP1 and CP2) showed a significantly (p<0.05) elevated protease activity, whereas the opposite trend was noticed for amylase activity. The aminotransferase activities of the liver and muscle were reduced linearly (p<0.05) with reduced dietary CP levels. Serum glucose and cholesterol contents elevated linearly (p<0.05) with decreased dietary CP levels. Whereas, the hemoglobin content and RBC count decreased (p<0.05) in the high CP-fed juveniles. The second-order polynomial regression analysis revealed that the optimal dietary CP levels could range from 311.1 to 318.0 g/kg for GIFT juveniles reared in ISW of 10 ppt salinity. Furthermore, by adopting the ideal protein concept, the CP levels in the diet of GIFT juveniles could be reduced from 373.6 to 311.1 g/kg without affecting growth performance. The outcome of this study will assist in developing a low-protein feed with balanced essential amino acids for GIFT culture in ISW.

Improved digestibility of black gram leaf meal based diets for rohu (Labeo rohita) with supplementation of exogenous enzyme cocktail

Leaf meal is currently the most cost-effective source of protein and energy for use as a supplement in fish feed. The drawback associated with integrating it into the fish diet pertains to the presence of anti-nutritional elements that must be eliminated through a viable approach such as the addition of exogenous enzymes for achieving optimal fish production. Consequently, a 60-day feeding trial was conducted to evaluate the black gram leaf meal (BGLM) as a potential ingredient to replace de-oiled rice bran (DORB) in the diet of Labeo rohita juveniles and reported for the first time. Three hundred acclimatized juveniles (average weight 11 ± 0.09 g) were allocated randomly into ten treatment groups in triplicate. Ten iso-nitrogenous (32 %) and iso-lipidic (6 %) diets were made with varying degrees of BGLM inclusion by gradually replacing DORB without or with exogenous enzyme mixture (E) of protease, xylanase, and phytase at a ratio of 1:1:1 viz. Control (40 % DORB, 0 % BGLM), BG10 (30 % DORB, 10 % BGLM), BG20 (20 % DORB, 20 % BGLM), BG30 (10 % DORB, 30 % BGLM), BG40 (0 % DORB, 40 % BGLM) & CE (C + 0.1 % E), BG10E (BG10 + 0.1 % E), BG20E (BG20 + 0.1 % E), BG30E (BG30 + 0.1 % E), BG40E (BG40 + 0.1 % E) were prepared. Fish fed with BG20E diet exhibited maximum growth rates, nutrient utilization and digestibility co-efficient of the diet (P<0.05) however these were similar in C+E treatment (P>0.05). Inclusion of 20 % or more BGLM without enzyme cocktail significantly (P<0.05) decreased the nutrient utilization and growth performance of L. rohita. The dry matter and nutrient digestibility of the experimental diet were significantly decreased (P<0.05) with the inclusion of 20 % or more BGLM in place of DORB, however supplementation of exogenous enzyme cocktail significantly increase (P<0.05) the digestibility and highest was recorded in BG20E. The present study concluded that supplementation of exogenous enzyme cocktail (protease, xylanase, and phytase) increase the digestibility of BGLM and increases its inclusion level up to 30 % in the diet of L. rohita, however, 20 % BGLM supplemented with enzyme cocktail registered the best growth, nutrient utilization and digestibility coefficient of the diet.

The effects of Lactobacillus plantarum and oxolinic acid on growth, immune-related genes, and gut bacterial community structures in juvenile Japanese eel (Anguilla Japonica)

This research aims to understand the distinct effects of Lactobacillus plantarum and Oxolinic Acid on the growth, immune-related genes, and gut bacterial community structures of juvenile Japanese eel.In this study, the Lactobacillus plantarum strain MH079448 was added to the diet for Japanese eel juveniles as test group (LP), with no bacteria administrated as control group (CK). Meanwhile, the antibiotic Oxolinic Acid immersion treatment was administrated in an extra group as a comparison for alternative evaluation (OA). The mRNA levels of toll-like receptors 2 (TLR-2) and tumor necrosis factor-alpha (TNF-α) in livers and gills of Japanese eel were analyzed by qRT-PCR technology. The intestinal microbiota was analyzed by High-throughput Sequencing (HTS) analysis.The results showed that at the end of experiment, the specific growth rates (SGR) and weight-gain rate (WGR) of Japanese eels in both LP and OA were improved to an approximately equal level, viz., 38.38 ± 15.2%, 1.18 ± 0.39%/d and 43.67 ± 16.52%, 1.29 ± 0.39%/d, respectively, which were significantly higher than the CK (8.73 ± 4.81%, 0.3 ± 0.16%/d) (p < 0.05). At the beginning of the experiment, there were no significant differences in the expression levels of TLR-2 and TNF-α in the gill and liver (p > 0.05). However, on day 28, compared with CK, both LP and OA showed significant upregulation in the expression levels of TLR-2 and TNF-α in the gill. Specifically, there was no significant difference in the expression levels of TLR-2 between LP and OA in the gill (5.97 ± 0.33 and 5.73 ± 0.38 respectively) (p > 0.05), while TNF-α exhibited significant differences in the gill (3.40 ± 0.24 and 4.96 ± 0.17 respectively) (p < 0.05). In the liver, on day 28, LP showed significant upregulation in the expression levels of TLR-2 and TNF-α (0.079 ± 0.006 and 0.116 ± 0.018, respectively) (p < 0.05). Concerning the TLR-2 in the liver of OA, it showed significant upregulation to 0.132 ± 0.009 (p < 0.05), which was significantly higher than that of LP (0.079 ± 0.006) in the liver(p < 0.05). However, on day 28, compared with CK and LP (0.049 ± 0.04 and 0.116 ± 0.018, respectively), the expression level of TNF-α in OA of liver was significantly downregulated (0.039 ± 0.002) (p < 0.05).Further, at the end of the experiment, Gammaproteobacteria was still the dominant class in CK and OA with the relative abundance of 95.09% and 92.49%, correspondingly, whereas in the LP, its value dropped to 82.79%. Compared to CK, the relative abundance of total probiotics in LP were increased by 1.619%, but it decreased by 0.464% in OA. Their total (opportunistic) pathogens in LP and OA were decreased by 4.562% and 16.803%, respectively. Functionally, compared to CK, the predicted functions of intestinal microbiota, such as energy metabolism, nutrient absorption and secondary metabolites were significantly enhanced in both LP and OA(p < 0.05). The results of this study firstly demonstrated that compared to Oxolinic Acid, Lactobacillus plantarum MH079448 approximately equally improved the growth performance, and approximately equally enhanced immune response. However, concerning the optimized community structures of intestinal microbiota in juvenile Japanese eels, Lactobacillus plantarum MH079448 was better than Oxolinic Acid, especially in relative abundance of total probiotics improvement.

Can biochemical tracers reveal ontogenetic trophic shift and individual prey selection in white sharks from Guadalupe Island, Northeast Pacific?

Refining the role of apex predators in marine food webs is a necessary step in predicting the consequences of their global decline under the footprint of fishing activities. White sharks (Carcharodon carcharias) are vulnerable predators, performing large migrations and able to forage on a variety of prey in different habitats. In the Northeast Pacific, juvenile and adult white sharks are found seasonally at the same aggregation sites, such as Guadalupe Island off Mexico. While adults are thought to target local pinniped colonies, very few predator-prey interactions have been documented and the diet of juveniles in this area remains poorly understood. Here we used carbon/nitrogen stable isotopes and fatty acids to characterize the trophic ecology of white sharks at Guadalupe Island. In contrast to the ontogenetic trophic shift paradigm, we detected no influence of size on muscle stable isotope and fatty acid composition, revealing no significant dietary variation between juvenile and adult sharks. Stable isotopes did not allow definitive conclusions to be drawn regarding the diet of white sharks at Guadalupe Island, due to significant variability in the contribution of different potential prey depending on the trophic discrimination factors used. However, most sharks were rich in polyunsaturated fatty acids (such as long-chain omega 3), suggesting a local diet of mainly pelagic prey (potentially large fish or cephalopods). A few individuals appeared to show recent consumption of pinnipeds, with higher proportions of saturated and monounsaturated fatty acids. These individual differences in fatty acid composition could reflect an ecological trade-off between consumption of prey rich in fat (marine mammals) versus prey rich in polyunsaturated fatty acids (pelagic prey), respectively meeting the energetic and physiological needs of white sharks. Although ontogenetic trophic changes were not able to be discerned, our results provide new insights into the physiological drivers of predator-prey interactions, which can benefit the definition of conservation strategies in a changing ocean.

Effects of mesterolone on the sex ratio, physiology and liver function of juvenile tambaqui (Colossoma macropomum)

In fish, sex dimorphism generates benefits for farming when one gender displays better production traits than the other. In such cases, farming exclusively one sex becomes more profitable. The tambaqui (Colossoma macropomum) is the Brazilian native species with the highest production in the Brazilian fish industry. In tambaqui farming, it is more lucrative to produce females because they grow faster than males. As the species has the XX/XY genetic sex determination system, the use of XX neomales (masculinized genetic females) as breeders to produce solely all-female populations is the most sustainable approach. With the aim of obtaining tambaqui neomales, we tested three doses of mesterolone (1-α-methylandrosterone; at 10, 20 and 40 mg kg−1) through the diet of pre-differentiated juveniles for three months, to masculinize the females. The sex ratio and immediate and long-term effects on the physiology of the fish were evaluated by hematological and biochemical analyses of the blood plasma at the end of the treatment, and three months later. Possible hepatotoxic and mutagenic effects of mesterolone were assessed via liver histopathology, hepatic enzyme production and the micronucleus test (fragmented DNA) in the erythrocytes. The results indicate that 20 and 40 mg kg−1 of mesterolone produced over 76% phenotypic males, have no influence on growth and on the biochemical parameters, do not cause DNA damage, nor do they have toxic effects in the liver of tambaqui. A decrease in the hepatosomatic index and an increase in some hematological parameters were observed during the treatment, but all values were similar to the control three months after the end of the experiment.

In vitro evaluation of algae and their effect as dietary ingredient on growth, chemical composition and intestinal functionality in juvenile turbot (Scophthalmus maximus)

The objectives of this study were to evaluate the in vitro protein hydrolysis of five algae (Arthrospira sp., Chlorella sp., Tisochrysis sp., Microchloropsis sp. and Ulva rigida) by the digestive proteases of Scophthalmus maximus, and to assess the effect of feeding turbot juveniles on diets supplemented with these algae in a 60-day feeding trial. The in vitro results revealed that algal protein was hydrolysed by turbot digestive proteases. Besides, the quantification of total amino acids released during the in vitro hydrolysis evidenced noticeable amino acid bioavailability, mainly in the case of Arthrospira sp. with up to 42.7% of the amino acids released after 120 min of in vitro hydrolysis. However, the structural characteristics of cell wall of each species influenced the protein accessibility as evidenced by the lower values obtained in Microchloropsis sp. For the in vivo feeding trial, 255 specimens of turbot, with an average initial weight of 26.4 ± 7.6 g, were used, and were fed with diets including 5% and 10% of a blend of the same microalgae tested in vitro (M5 and M10) or U. rigida (U5 and U10), compared to a control feed without algal biomass (CT). At the end of the feeding trial, growth performance and nutrient utilization did not show differences among the experimental groups. In addition, the fish fed with the diets supplemented with algae showed lower lipid oxidation in the muscle, and an improvement in digestive functionality, as the activity of pancreatic and intestinal enzymes increased. The ultrastructural study of the intestinal mucosa revealed an increase in the length of the microvilli and the absorptive surface in fish fed with the algae-supplemented diets, as well as decreased thickness of the lamina propria and the number of goblet cells. These results confirmed that the supplementation of turbot juvenile diets with low percentage of microalgae or U. rigida is appropriate for improving digestive functionality, as well as reducing the oxidation of lipids in the muscle.

A biofloc system avoids the adverse effects of diets with suboptimal protein levels on zootechnical performance, intestinal histomorphometry, and protein metabolism of Nile tilapia juvenile fed Spirulina biomass (Arthrospira platensis) as an alternative protein source.

This study aimed to evaluate the effect of the biofloc technology (BFT) system and the replacement of fish meal with Spirulina biomass on productive performance, intestinal histomorphometry, plasma biochemistry, and oxidative stress of Nile tilapia juveniles (Oreochromis niloticus) fed suboptimal levels of protein. Two factors were evaluated: production systems (clear water × BFT) and replacement of fish meal with Spirulina (0, 33, 66 e 100%). The design was in a 2 × 4 randomized factorial scheme with four replications, and the fish were evaluated for 48days. Four isoproteic (28% crude protein) diets were formulated with gross energy values close to 4300kcalkg-1. Nile tilapia juveniles (0.23 ± 0.01g) were distributed in 16 circular tanks (70 L) at seven fish/tank. The diets were formulated with protein levels approximately 20% below that required for the species and life stage. No interaction was observed between the factors evaluated (production systems × Spirulina inclusion). Rearing the fish in the BFT system avoided the adverse effects of diets with suboptimal protein levels on performance, intestinal histomorphometry, and protein metabolism. Lower values lower lipid peroxidation and higher antioxidant capacity were observed in fish reared in the BFT system, showing evidence of improvements in antioxidant responses and lower levels of physiological oxidative stress. Spirulina completely replaced fish meal in the diets of Nile tilapia juveniles without adverse effects on intestinal morphometry, protein metabolism, and antioxidant response. Replacing 66% of fish meal with Spirulina improved the productive performance, regardless of the rearing system.

Paedomorphosis and retention of juvenile diet lead speciation in a group of Neotropical snakes (Colubroides-Philodryadini)

Dipsadidae is one of the largest clades of extant reptiles, showing an impressive morphological and ecological diversity. Despite this fact, the developmental processes behind its diversity are still largely unknown. In this study, we used 3D reconstructions based on micro-CT data and geometric morphometrics to evaluate the skull morphology of Philodryas agassizii, a small, surface-dwelling dipsadid that consume spiders. Adult individuals of P. agassizii exhibit a cranial morphology frequently observed in juveniles of other surface-dwelling colubroideans, represented in our analysis by its close relative Philodryas patagoniensis. Large orbits, gibbous neurocranial roof and a relatively short jaw complex are features present in juveniles of the latter species. Furthermore, we performed an extensive survey about diet of P. patagoniensis in which we detected an ontogenetic dietary shift, indicating that arthropods are more frequently consumed by juveniles of this dietary generalist. Thus, we infer that P. agassizzii retained not only the ancestral juvenile skull morphology but also dietary preferences. This study reveals that morphological changes driven by heterochronic changes, specifically paedomorphosis, influenced the retention of ancestral life history traits in P. agassizii, and therefore promoted cladogenesis. In this way, we obtained first evidence that heterochronic processes lead speciation in the snake megadiverse clade Dipsadidae.

Diet‐dependent reproductive investment in gumleaf skeletonizer moths, Uraba lugens

AbstractJuvenile diet can profoundly affect subsequent adult development, morphology and reproductive investment. Yet, little is known about how juvenile diet affects adult investment into chemical‐based sexual signalling, perhaps due to the historical assumption that pheromone production is not costly. We explored how juvenile diet influenced the reproductive investment of adults in the gumleaf skeletonizer moth, Uraba lugens. Juveniles were reared on different host plant species (Eucalyptus camaldulensis and Eucalyptus moorei) and on E. moorei host plants with different fertilizer treatments (fertilized and non‐fertilized). These juvenile diets differ in foliage carbon and nitrogen content. Several adult life history traits were influenced by juvenile diet, including body size in females, and longevity in males. However, we found no evidence from Y‐maze olfactometer assays that diet affected the attractiveness of female pheromones to males. Finally, host plant species affected male pre‐copulatory investment: males reared on E. moorei had longer antennae, but less dense sensilla. Combined, our experiments suggest that the effects of juvenile diet on investment in reproductive traits, including those associated with signalling, differ between males and females. Females allocate nutrients to adult body size, which determines fecundity. In contrast, males allocate nutrients to adult longevity and antennae size, both of which improve mate search and mating success.

Avian trematodes of central European corvids are heterogeneous regarding preferences for host species and age.

Corvids are highly adaptive birds that respond well to anthropogenic changes in their environment. Trematode communities of corvids were studied mainly in the 1950s through 1970s in regularly flooded parts of the Volga River delta in Russia; more recent studies and data from other regions where the corvids are in less contact with postflooding habitats are limited. Data for Corvus corax were lacking. Using our samples obtained from 1963 to 2023, we performed a large-scale analysis of trematode species composition and community structure in Corvus frugilegus, Corvus cornix, C. corax, Coloeus monedula, Pica pica, and Garrulus glandarius; all originated from the Czech Republic. We identified corvids as hosts of mutually overlapping component communities of only a few species of trematodes (Brachylecithum lobatum, Lyperosomum petiolatum, Lyperosomum longicauda, Tamerlania zarudnyi, Urogonimus macrostomus), with the presence of many rare and incidental findings of other trematode species. Only a few species used corvids as their core hosts (L. longicauda and B. lobatum). Trematode component communities in first-year birds included Prosthogonimus cuneatus, Prosthogonimus ovatus, Plagiorchis asperus, and Morishitium dollfusi due to an increased share of insects (intermediate hosts of Prosthogonimus and Plagiorchis) and snails (intermediate hosts of Morishitium) in the diet of juveniles. The trematode component communities of corvid species overlapped but were heterogeneous at the level of host individuals, likely reflecting differences in food sources related to the respective host ages and nesting sites.

Dental diseases and dental wear as a proxy for dietary patterns in Hellenistic-early Roman Menainon, Sicily

ObjectiveThis paper explores dental diseases and wear as a proxy for dietary patterns in Hellenistic-early Roman Menainon. MaterialsThis study includes 166 individuals (4th-1st c. BCE). MethodsCarious lesions, dental calculus, antemortem tooth loss, and dental wear were recorded to explore male-female and adult-juvenile differences, and to position Menainon in the broader Hellenistic/early Roman world through comparisons with published data from other sites. ResultsMales and females showed similar rates of dental diseases. Dental wear, in contrast, was systematically greater in males. Caries rates were high in both adults and juveniles, but adults showed more calculus. The population from Menainon had higher frequencies for calculus and carious lesions compared to contemporary Italian and Greek assemblages, and a similar frequency for antemortem tooth loss. ConclusionSome sex-related differences in the dietary patterns of the Menainon population were visible but small. The diet of adults and juveniles must have been similar in terms of carbohydrate consumption but different with regard to protein consumption. The high frequency of carious lesions and calculus compared to other Greco-Roman sites suggests that this population must have had good access to dietary resources (protein and carbohydrates). SignificanceThis paper provides insights on gender (sex-related) and age divisions in the Hellenistic/early Roman society through the exploration of food consumption in a Sicilian assemblage. LimitationsDividing the assemblage by sex and age group reduced considerably the sample size. Suggestions for further researchStable isotopes and dental microwear analyses should be used to investigate dietary patterns further.

Effects of Dietary Sodium Propionate on Growth, Digestive Enzyme Activity, and Expression of Immune System Genes in Juveniles of Tropical Gar (Atractosteus tropicus)

We determined the effects of sodium propionate (SP) added to the diets of Atractosteus tropicus juveniles with respect to the growth, survival, digestive enzyme activity, and expression of genes that are associated with the immune system. Five treatments (0, 0.5, 1.0, 1.5, and 2.0%) were evaluated in triplicate on 180 fish (3.65 ± 0.12 g) distributed among 15 (70 L) tanks. The juveniles were fed five times a day with 5% feed in relation to the biomass of the organism. The treatment with 0.5% SP showed a final weight value of 25.7 ± 4.5 g, absolute weight of gain (AWG) of 21.93 ± 4.39 g, and specific growth rate (SGR) of 3.1 ± 0.26. Treatments with 1.5 and 2.0% SP showed the highest survival (91.6%). The control group (0%) showed a greater activity of lipases. There was a tendency that the highest activity of alkaline proteases and chymotrypsin occurred in the 0 and 0.5% treatments. The maximum relative expression of the genes ocln, muc2, and nod2 occurred in the 1.5% treatment. The inclusion of SP in the diet of A. tropicus juveniles could benefit the activity of some digestive enzymes as well as the expression of genes related to the function of the intestinal barrier, therefore benefitting the survival of the organisms.

Use of black soldier fly (Hermetia illucens) larvae meal in diets for gilthead seabream juveniles: Effects on growth-related gene expression, intermediary metabolism, digestive enzymes, and gut microbiota modulation

A study was conducted to evaluate the effects of dietary inclusion of defatted Hermetia illucens larvae meal (HM) on the expression of growth-related genes, plasma metabolites, activity of intermediary metabolism enzymes, and gut microbiota modulation in gilthead seabream (Sparus aurata) juveniles. Four experimental diets were formulated (43% crude protein, 18% crude lipids) with increasing levels of defatted HM: 0 (HM0), 15 (HM15), 30 (HM30), and 45% (HM45) replacing fishmeal (included at 34% in the control diet) at 0, 22, 60, and 100%, respectively. Fish were fed these diets for 67 days. At the end of the trial, the expression of muscle growth hormone receptors (ghr1 and ghr2), insulin-like growth factors (igf1 and igf2), cathepsins (cts-a and cts-b), and myogenic determination factor 1 (myod1) were not affected, while a downregulation of myogenic determination factor 2 (myod2) and upregulation of myostatin (mstn) was observed with HM inclusion. Plasma metabolites profile was unaffected by diet composition, except for a linear decrease trend in total lipids. A linear increase of liver alanine aminotransferase (ALT) and glutamate dehydrogenase (GDH) activity and a linear decrease of glucose 6-phosphate dehydrogenase (G6PDH), malic enzyme (ME), and (FAS) activity were observed with HM inclusion. The activity of β-hydroxy acyl-CoA dehydrogenase (HOAD) followed a quadratic trend, being higher in fish fed with diet HM15 than in the control. Likewise, amylase, trypsin, and chymotrypsin activity were higher in the posterior intestine of fish fed with diet HM15. Digesta of fish fed the HM-containing diets showed an increase in the number of operational taxonomic units, microbial richness, and diversity. Conversely, a reduction in these indexes was observed in the mucosa. Among the identified bacteria, Firmicutes represented the predominant phyla. The inclusion of HM increased the abundance of Oceanobacillus, Lederbergia, Bacillus, and Corynebacterium in the digesta while Lactobacillus and Caldalkalibacillus abundance was reduced. Overall, total FM replacement with defatted HM had no major effects on plasma metabolites and muscle growth-related genes but induced a few differences in intermediary metabolism and digestive enzymes activity. HM inclusion improved gut digesta microbiota richness and diversity, promoting the growth of potential beneficial bacteria.

Effect of green seaweed meal blend on feed quality and zootechnical performance in shrimp (Penaeus vannamei) juveniles

Aim of study: To evaluate a green seaweed meal in the diets of Penaeus vannamei juveniles, comprising Ulva spp., Caulerpa spp. and Enteromorpha spp. as a feed blend at inclusion levels at 4% and 8%. Area of study: Universidad Nacional Agraria La Molina, Lima, Perú. Material and methods: Analyses were conducted to determine the pellet quality through percentages of dry matter retention (DMR), protein loss and water absorption capacity; and to evaluate the effect of this seaweed meal in the digestibility and zootechnical shrimp performance. Three treatments (diets) were formulated to contain 0% (control diet), 4% (M4) and 8% (M8 of green seaweed meals (blend)), in isonitrogenous (crude protein; 300 g kg-1) and isocaloric (3.3 Mcal kg-1) diets. The shrimps were reared at a density of 286 juveniles m-3 for 29 days in a recirculating aquaculture system (RAS). Main results: Among the diets, M4 had the highest DMR value (97.06%), whereas M8 had highest water absorption capacity (185.48%) with lower % of protein loss between the treatments diets. No differences were observed in the zootechnical performance, except for survival (p&lt;0.05), with the M8 diet having highest mortality rate (44.4%) between the treatments diets. Research highlights: Incorporating 4% green seaweed meal in shrimp feed supported adequate growth and survival of juvenile P. vannamei with adequate DMR values, water absorption capacity, protein loss and high apparent dry matter digestibility and apparent digestibility of the reference diet.

Biofloc technology and cockroach (Nauphoeta cinerea) insect meal-based diet for Nile tilapia: zootechnical performance, proximate composition and bacterial profile

Abstract Different inclusion levels of cockroach meal Nauphoeta cinerea (CM) were investigated in diets for tilapia (Oreochromis niloticus) reared in biofloc systems in substitution of the soybean meal. Five treatments were evaluated (0, 5, 10, 15 and 20% of CM inclusion) using three experimental units per treatment. The experiment lasted for five weeks with units stocked with 10 juveniles (3.00±0.25 g) per replicate. Water quality, zootechnical performance, bacteriological profile, and proximate composition were analyzed and monitored. Zootechnical data was submitted to a regression analysis up to second order. No differences were verified regarding feed conversion, survival and productivity. The CM presented high protein levels (66.84%), high estimated gross energy (5270 kcal kg−1), low lipids (6.07%) and mainly long-chain saturated fatty acids. Different bacteriological profiles were identified including species which may be potentially pathogenic and responsible for degrading organic matter. The overall results indicated that it is possible to include CM up to 10% in diets for tilapia juveniles raised in biofloc systems.

The Application of Moringa oleifera Leaf Meal and Its Fermentation Products in the Diet of Megalobrama amblycephala Juveniles

This study assessed the potential applicability of Moringa oleifera leaf meal (MO) and fermented Moringa oleifera leaf meal (FMO) as feed supplements for aquatic animals. Five experimental diets, including the basal diet (control), 2.2% and 4.4% MO-supplemented diets (MO2 and MO4), and 2.2% and 4.4% FMO-supplemented diets (FMO2 and FMO4), were prepared for feeding Megalobrama amblycephala juveniles. After the eight-week feeding trial, the growth performance, muscle nutritional composition, plasma and hepatic biochemistry indicators were measured. The results demonstrated that MO and FMO had no detrimental effects on the growth performance of M. amblycephala juveniles. The muscle crude protein, crude lipid, and total free amino acids contents were significantly enhanced in the FMO4 group (p &lt; 0.05). The liver acetyl-CoA carboxylase α mRNA level was significantly increased and the lipoprotein lipase mRNA level was markedly reduced in the FMO4 group (p &lt; 0.05). Therefore, the FMO4 group exhibited a significant increase in plasma low-density lipoprotein cholesterol and triglyceride levels (p &lt; 0.05). Compared to the control group, total superoxide dismutase and catalase activities were significantly increased in the FMO4 group (p &lt; 0.05). The FMO2 and FMO4 groups exhibited an anti-inflammatory response by inhibiting the expression levels of toll-like receptor 4, nuclear factor-kappa B, and tumor protein P53 mRNA (p &lt; 0.05). In conclusion, the 4.4% FMO treatment increased muscle crude protein content, enhanced lipogenesis, and improved the hepatic antioxidant abilities of M. amblycephala juveniles, while 2.2% FMO and 4.4% FMO improved the liver anti-inflammatory capacities.

The prebiotic effect of agavin inclusion levels in low fishmeal diets for Totoaba macdonaldi juveniles

The prebiotic effects of dietary agavin on growth performance, feed efficiency and digestibility, digestive enzyme activity, and distal intestine integrity in low fishmeal diets for Totoaba macdonaldi juveniles were evaluated in the present study. For this purpose, totoaba juveniles with a mean initial weight of 29 ± 1 g were fed for 56 days with four experiential diets formulated to replace fishmeal (FM) and poultry by-product meal (PBM) with soybean meal (SBM). The reference diet (RD) contained FM and PBM solely as the primary protein source. The following three diets contained SBM included at 240 g kg−1 with graded levels of agavin; 10, 20, and 30 g kg−1, in order to determine if a lower or higher quantity of the prebiotic in the diet would maximize growth parameters and fish intestinal integrity and reduce putative adverse effects of SBM in the diet. The inclusion of agavin in the diet, independently of the inclusion level, resulted in higher growth performance without significant differences in feed utilization and nutrient digestibility compared with the RD. Acid proteases (i.e., pepsin-like), trypsin, and total alkaline proteases activities resulted in significant differences among treatments but were not correlated with growth improvements. In terms of the intestinal health, significant differences in the number of mucosal folds and brush border height were found among dietary treatments and the light microscopy images and our semi-quantitative scoring revealed that agavin prevented the typical alterations in the distal intestine morphology associated with SBM induced enteritis in totoaba juveniles after 56 days of feeding. Thus, based on the results from the present study a 1 % agavin is recommended as the minimum dietary inclusion level in a low fishmeal diet (18 % FM) containing 24 % SBM to prevent typical symptoms of enteritis in totoaba juveniles under culture conditions.