Microbound Diets Research Articles

Development of microbound diet and its application on Macrobrachium rosenbergii larvae and postlarvae

The aquaculture sector actively seeks innovative methods to enhance growth and nutrition in aquatic organisms. Microbound diets (MBDs), known for their finely ground pellets often combined with binders to encapsulate nutrients are gaining prominence. This study aimed to develop an MBD and assess its impact on the growth and body composition of giant freshwater prawn, Macrobrachium rosenbergii larvae and postlarvae (PL) through two feeding trials. Various binders (agar, zein, alginate, carrageenan, and carboxymethyl cellulose) were tested during the development of MBD and were compared with live feed (rotifer). The first feeding trial demonstrated improved larval growth with MBD with agar, reaching an average of Stage XII, compared to those fed the control diet, which only reached Stage IX. The second feeding trial investigated the effect of feeding regimes on giant freshwater prawn PL, consisting of (i) one-time feeding in the morning, (ii) one-time feeding at night, (iii) two-time feeding, (iv) three-time feeding, and (v) four-time feeding. Results showed that two-time feeding had comparable survival rates and growth performance to three-time feeding (survival rate= 43–45 % and weight gain= 0.09–0.11 g), with the best feed conversion ratio in two-time feeding (1.70) and the highest level of highly unsaturated fatty acids (25–26 %) in PL fed one-time and three-time. Overall results suggest that MBD with agar holds promise as a binder with two-time and three-time feeding, enhancing the quality of giant freshwater prawn PL. Further research on extending the duration of the experiment is recommended to assess PL moulting patterns and performance, as varied feeding regimes may significantly impact growth and moulting.

Tragacanth Gum and Linseed Gum as Adhesives Improved the Survival, Digestive Function, Antioxidant Enzyme Activities, and Immunity in Large Yellow Croaker (Larimichthys crocea) Larvae

A 30-day feeding experiment was designed to investigate the effects of different adhesives on survival, growth performance, digestive enzyme activities, antioxidant capacity, and inflammation response of large yellow croaker (Larimichthys crocea) larvae (initial weight 8.40 ± 0.18 mg). Four iso-nitrogenous (55% crude protein) and iso-lipidic (22% crude lipid) microbound diets (MBD) were formulated to contain 2% sodium alginate (SA), 2% tragacanth gum (TG), 2% linseed gum (LG), and 2% poloxamer (PX), respectively. Results showed that larvae fed with TG and LG diets had significantly higher survival rate than the larvae fed with SA and PX ( P < 0.05 ). Larvae fed with the PX diet had lower final weight and specific growth rate than the other groups ( P < 0.05 ). Larvae fed with TG diet had significant higher activities of lipase in pancreatic segments and trypsin in intestinal segments than the larvae fed with the PX ( P < 0.05 ). Meanwhile, the lipase activities of larvae fed with LG was significantly higher in intestinal segments than those fed with SA and PX diets ( P < 0.05 ). Larvae fed with TG and LG diets had significantly higher activities of AKP in brush border membranes than larvae fed with SA and PX diets ( P < 0.05 ). Moreover, the mRNA expression of pcna and zo-1 increased, respectively, in larvae fed TG and LG diets compared with the other groups ( P < 0.05 ). Larvae fed with LG and TG diets had significantly higher activities of SOD and T-AOC than those fed with PX diet ( P < 0.05 ). The content of GSH increased significantly in larvae fed with SA, TG, and LG diets compared with PX treatment ( P < 0.05 ). The activities of iNOS significantly increased in larvae fed with TG and LG diets compared to other groups ( P < 0.05 ). Meanwhile, the mRNA expression of il-10 significantly increased in TG and LG groups ( P < 0.05 ). In conclusion, results of the study demonstrated that TG and LG can be used as feed binders for microdiets with positive effects on survival, activities of digestive enzymes, antioxidant capacity, and inflammatory response. However, PX inhibited the survival and growth, and further study is needed to determine the suitable usage and dosage.

A Review of the Nursery Culture of Mud Crabs, Genus Scylla: Current Progress and Future Directions.

Simple SummaryNursery culture knowledge is important for successful commercial seed production especially for mud crab, genus Scylla, a highly valued delicacy. The aim of this review paper is to summarise the status and information on the current nursery culture stage of the mud crab. Various aspects of mud crab hatchery described in this paper are expected to facilitate practitioners and lay people to easily understand a mud crab nursery. This review also provides guidelines for researchers in conducting future research and development on a mud crab nursery in order to increase the production of mud crab crablets for the farming industry.The nursery stages of mud crab, genus Scylla, proceed from the megalopa stage to crablet instar stages. We review the definition and several of the key stages in mud crab nursery activities. The practice of the direct stocking of megalopa into ponds is not recommended due to their sensitivity. Instead, nursery rearing is needed to grow-out mud crabs of a larger size before pond stocking. Individual nursery rearing results in a higher survival rate at the expense of growth and a more complicated maintenance process compared with communal rearing. The nursery of mud crabs can be done both indoors or outdoors with adequate shelter and feed required to obtain a good survival percentage and growth performance. Artemia nauplii are still irreplaceable as nursery feed, particularly at the megalopa stage, while the survival rate may be improved if live feed is combined with artificial feed such as microbound diet formulations. Water quality parameters, identical to those proposed in tiger shrimp cultures, can be implemented in mud crab rearing. The transportation of crablets between different locations can be done with or without water. The provision of monosex seeds from mud crab hatcheries is expected to become commonplace, increasing seed price and thus improving the income of farmers. Numerous aspects of a mud crab nursery including nutrition; feeding strategies; understanding their behaviour, i.e., cannibalism; control of environmental factors and practical rearing techniques still need further improvement.

Elucidating an optimal diet for captive Acropora corals

Developing an optimal heterotrophic feeding regime has the potential to improve the growth and overall health of captive corals. This study evaluated the efficacy of seven unique feeding strategies for Acropora loripes, Acropora millepora, and Acropora tenuis nubbins: a novel, micro-bound diet (ATF), a novel, dissolved diet rich in long-chain polyunsaturated fatty acids (LC-PUFA) (LONG), a novel, dissolved diet lacking in LC-PUFA (SHORT), a phytoplankton diet of Isochrysis galbana (ALG), co-feeding of LONG and ALG (COMB), unfiltered seawater (RAW), and an unfed treatment of filtered seawater only (CTL). After 90 days, all species showed the highest growth in the ALG treatment. There was a negative correlation between growth and total lipid concentration, indicating that Acropora corals have a low tolerance for lipid-rich diets. Coral appeared to perform best in the relatively natural treatments, namely the ALG, CTL, and RAW, which recorded higher growth and increased proportions of high-energy lipid compounds such as wax esters, triacylglycerols, and the fatty acids, 16:0 and 22:6n-3. Meanwhile the formulated diets (ATF, LONG, SHORT) promoted greater proportions of structural lipids and indispensable, membrane-bound fatty acids including 20:5n-3 and 20:4n-6. Despite the SHORT diet being low in LC-PUFA, corals fed this diet showed few significant differences in several individual LC-PUFA compared to most other treatments, suggesting that these were obtained via de novo synthesis, or selectively retained from initial reserves. Ultimately, this study showed that phytoplankton represents a promising vehicle of nutrient delivery for captive Acropora corals.

Interaction between taurine, vitamin E and vitamin C in microdiets for gilthead seabream (Sparus aurata) larvae

The negative effects of oxidative damage on larval development, growth and survival are among the factors markedly affecting marine fish larvae production success. Whereas α-tocopherol (vit E) and l-ascorbic acid (vit C) are strong antioxidants, the potential antioxidant role of taurine (Tau) in fish diets and its relation with other antioxidant nutrients needs further clarification. The present study aimed to determine the potential interactions between the dietary levels of vit E plus vit C and Tau on survival, growth, bone development and oxidative metabolism in gilthead seabream larvae. Six micro-bound diets containing two levels of Tau combined with three levels of vit E plus vit C were manually fed 24 times/day to 16 dph larvae for 15 days. Elevation of dietary vit E and vit C over 3000 mg/kg, led to unbalanced body vit C/vit E ratio and up-regulation of genes coding for antioxidant enzymes, the highest incidence of bone anomalies and the lowest larval survival. Increase in dietary vit C + vit E up to 1800 mg/kg, down-regulated GPX expression, up-regulated OC expression and reduced maxillary bone anomalies. Increase in dietary Tau up to 7.1 g/kg significantly improved larval growth, down-regulated antioxidant enzyme genes and reduced the incidence of bone anomalies. Moreover, the pro-oxidative effects of the high supplementation of vit C and E where mitigated by increase in dietary Tau levels. Finally, increase in dietary vit E, vit C and Tau up to 1783 mg/kg, 1921 mg/kg and 7 g/kg lead to the highest larval survival and growth, the highest OC gene expression and the lowest incidence of bone anomalies, including lordosis, kyphosis, branchiostegal and maxillary bones anomalies.

Effects of Dietary Lactobacillus plantarum on Growth Performance, Digestive Enzymes and Gut Morphology of Litopenaeus vannamei

A 15-day feeding trial was conducted to investigate the effect of dietary Lactobacillus plantarum on growth performance, digestive enzyme activities and gut morphology of juvenile Pacific white shrimp, Litopenaeus vannamei (initial body weight=7.96±0.59g). Four microbound diets were formulated to contain fermentation supernatant (FS), live bacteria (LB), dead bacteria (DB), and cell-free extract (CE) of L. plantarum. Results indicated that final weight was significantly higher in FS, DB, and CE group in comparison to the control group (P<0.05). The maximum weight gain rate (WGR) and specific growth rate (SGR) of the CE diet group were significantly higher than that of other groups (P<0.05). The FCR of CE diet group was lower than that of the control, LB, DB, and FS diets groups (P<0.05). The highest digestive enzyme activities (amylase, lipase, and pepsin activity) in the hepatopancreas and gut of shrimp were observed in the CE diet group. Histological study revealed that dietary CE diet could significantly increase the enterocytes height of shrimp. The administration of cell-free extract of L. plantarum could effectively improve the growth performance of L. vannamei via the improvement of digestive enzyme activities and the enterocytes height of shrimp. The results of this study will be essential to promote application of probiotics in shrimp aquaculture.

Feeding Larval Gulf Killifish: Total Replacement of Artemia Nauplii and Co‐Feeding from Hatch

AbstractLarval Gulf Killifish Fundulus grandis hatching from air‐incubated eggs are precocial, with well‐developed mouths and eyes providing an immediate capacity for exogenous feeding. Live feeds are almost universally used in finfish and crustacean hatcheries, with newly hatched brine shrimp Artemia spp. nauplii being a standard. Across two experiments from hatch in Gulf Killifish, we evaluated the ability to replace Artemia nauplii with prepared diets. Experiment 1 measured growth and survival from hatch through 8 weeks in larval Gulf Killifish fed either Artemia nauplii or one of five commercially available diets. Experiment 2 measured survival and SL of Gulf Killifish larvae at 5, 10, and 15 d posthatch among treatments consisting of animals fed Artemia nauplii, the best‐performing commercial diet from experiment 1, or an experimental microbound diet or “co‐fed” the microbound diet and Artemia. In experiment 1, Gulf Killifish larvae fed live Artemia nauplii exhibited growth that significantly outperformed commercially available formulated diets. Mean ± SE (SEM) survival (%) among treatments ranged from 51.1 ± 7.4 to 86.2 ± 2.1. Larvae fed one commercially prepared diet outperformed larvae fed the other four commercial diets in terms of growth. In experiment 2, mean SL was significantly different among treatments by 15 d posthatch. Mean ± SEM survival (%) across all treatments in experiment 2 ranged from 87.7 ± 0.8 to 99.2 ± 0.4. Results of these experiments are some of the first to document acceptable growth and survival of finfish larvae when Artemia nauplii are completely replaced with formulated diets from hatch. The distinctive larval biology of the study species in concert with the ability to air‐incubate the embryos were presumably important factors in the ability to completely replace Artemia nauplii from hatch.

Live prey enrichment and artificial microdiets for larviculture of Atlantic red porgy Pagrus pagrus

In the first experiment the effects of rotifer enrichment and feeding frequency on larval performance of red porgy Pagrus pagrus were studied. Larvae (2 days post-hatching=2dph) were fed s-type rotifers (∼20 rotifers/mL) enriched with one of the four different treatment media: Rotifer Diet (microalgae Nannochloropsis oculata and Tetraselmis chuii), DHA Protein Selco, Algamac 3000 (Schizochytrium sp.) and Algamac+ARA (arachidonic acid). Larvae were fed daily at full ration or twice daily at half ration. Larval growth and survival (mean=22.8%) were satisfactory through 16dph under all treatments; however, resistance to hyposaline challenge (Survival Activity Index=SAI) was positively correlated (P<0.01) with DHA concentration of rotifers, and SAI appeared highest in the Algamac+ARA treatment. In the second experiment the effects of Artemia enrichment on larval performance were compared from 18dph through pre-metamorphosis (33dph). Larvae were fed Artemia (0.5–3.0/mL) enriched with two different media Algamac 3000 and DC DHA Selco, or unenriched Artemia (control). Both media improved DHA levels in Artemia and growth and survival (36.7–54.6%) of larvae, while larvae fed unenriched Artemia showed poor growth and survival (5.2%). In the third experiment a University of North Carolina Wilmington microbound diet (MBD) and two commercial microdiets (Gemma Micro and Otohime) were evaluated. The MBD contained different protein sources (i.e., menhaden, squid and krill meal, soy protein concentrate) and attractants. Beginning 16dph, live feeds and microdiets were co-fed to three treatment groups of larvae: (1) Gemma, (2) MBD, and (3) Otohime. Larval performance on the UNCW-MBD was comparable to the commercial microdiets, with no significant differences in larval survival, DHA, or total n-3 PUFA content through 32dph. Results delineate more effective rearing protocols for larviculture of Atlantic red porgy juveniles.

Effect of graded levels of taurine on growth performance and Ptry expression in the tongue sole (Cynoglossus semilaevis) postlarvae

The effect of graded levels of dietary taurine on growth, enzyme activities and pretrypsinogen (Ptry) mRNA expression in the tongue sole postlarvae was evaluated in this study. Four microdiets supplemented with 0 (T0), 5 (T0.5), 10 (T1.0) or 20 (T2.0) g kg−1 taurine were prepared. These diets were fed to the postlarvae with an average initial body dry weight of 3.32 ± 0.06 mg for 28 days. Survival and growth performance of the tongue sole postlarvae were significantly (P < 0.05) influenced by dietary taurine. Survival rate of fish fed with 20 g kg−1 dietary taurine was significantly lower than other treatments. The growth of fish initially increased with increasing dietary taurine level and then decreased. Postlarvae fed with 10 g kg−1 dietary taurine showed the best growth performance. Trypsin activities showed a significant increase with increasing dietary taurine level and then reached a plateau, while amylase activities and alkaline phosphatase activities increased in the start with increasing dietary taurine and then decreased. Ptry mRNA expression was stimulated by dietary taurine. Excessive dietary taurine (20 g kg−1) had adverse effects on survival, growth, digestive enzyme activities of the experimental fish. The suggested dietary taurine supplementation in microbound diets was 10 g kg−1 for the tongue sole postlarvae.

Ontogenetic development of digestive enzymes in Sobaity sea bream Sparidentex hasta larvae under culture condition

Activities of the main enzymes involved in digestion (pepsin, trypsin, amylase, lipase and alkaline phosphatase) in Sobaity sea bream were studied from hatching up to the juvenile stages (40days after hatch, DAH). All enzyme activities except for pepsin were detected upon hatching, and their activity subsequently increased with age. Early presence of trypsin and amylase was attributed to a genetically programmed process. Trypsin exhibited fluctuating pattern (with tow peaks at 16 and 30DAH) triggered by food ingestion and was in response to the diet shifting during the rearing period. Both lipase and amylase activities were enhanced after the onset of the weaning depending upon the microbound diet components. Early presence and incremental trend of alkaline phosphatase from 5th DAH represented early maturation of enterocytes and consequently rapid growth of this species. Pepsin was first detected at 14DAH and showed a sharp increasing trend up to end of the experiment. Its progressive increase followed by a decrease in trypsin activity after accomplishing weaning exhibited a change in the digestive physiology to reach to an adult-type protein digestion. In conclusion, such early ontogenetic development of the above mentioned enzymes makes it possible to wean Sobaity sea bream larvae earlier than 25DAH in order to reduce live food usage and improve weaning efficiency. Statement of relevanceObtaining knowledge about digestive physiology makes it possible to quantify the capacity of larvae to digest and absorb different types of nutrients from live feed and/or microbound diets and to understand the right time to conduct weaning in Sobaity sea bream larvae earlier than what has been practiced in hatcheries in order to reduce live food usage and improve weaning efficiency.

Growth performance, survival and body composition of southern flounderParalichthys lethostigmalarvae fed different formulated microdiets

Three experiments were conducted to evaluate the effects of micro-bound diets (MBD) on southern flounder larvae. In experiment 1, four MBDs were formulated with different protein sources as follows: MBD 1: herring meal, MBD 2: menhaden meal, MBD 3: menhaden and squid meal; MBD 4: menhaden, squid and herring meal. In experiment 2, four MBDs were formulated as follows: MBD 5: menhaden, squid and herring meal; MBD 6: menhaden, squid, herring and attractants; MBD 7: menhaden, squid, herring and casein, and MBD 8: menhaden, squid, herring, casein and attractants. In experiment 3, three groups were maintained as follows: Group 1: live feed; Group 2: co-fed with MBD 6; and Group 3: MBD 6. In experiment 1 on 35 dph, survival and body weight (BW) of the fish fed MBD 4 was significantly higher than the MBDs 1 and 2. In experiment 2 on 34 dph, fish fed MBD 6 had significantly higher BW than the commercial microdiets. In experiment 3 on 21 dph, fish receiving only MBD had significantly lower survival than the other groups. Growth, survival and larval fatty acid composition suggested that co-feeding MBD 6, a mixture of marine protein sources plus attractants was more effective than the other MBDs.

Effects of dietary protein levels on the growth, survival, amylase and trypsin activities in large yellow croaker, Pseudosciaena Crocea R., larvae

A feeding trial was conducted to investigate the effects of dietary graded protein levels on the growth, survival, amylase and trypsin activities of large yellow croaker (Pseudosciaena crocea R.) larvae from 12 to 42 days after hatching (DAH). Five approximately isoenergetic microbound diets (16.65 MJ/kg diet) were formulated to contain different protein (47.1%, 52.0%, 57.1%, 62.2% and 67.5%) levels. Frozen copepods, containing 54.5% crude protein (CP), 6.0% crude lipid, 27.2% ash and 6.7% glycogen, were used as a control. Each diet was randomly fed to triplicate groups of larvae with an initial mean body weight of 1.76 ± 0.09 mg (mean ± SD) in 180 L white plastic tanks, and each tank was stocked initially with 3500 larvae. Both the survival and the specific growth rate (SGR) of large yellow croaker larvae significantly increased with increasing dietary protein level up to 57.1%, and decreased thereafter. Frozen copepods resulted in intermediate survival and low SGR compared with the other diets. Whole-body moisture and protein of larvae were not significantly affected by the dietary protein level. In contrast, whole-body lipid of larvae fed diet with 47.1% CP was significantly higher (P<0.05) than those from fish fed the diets containing more than 57.1% CP. Additionally, fish fed the frozen copepods had the lowest whole-body protein and lipid. The amylase-specific activity increased with increasing dietary carbohydrate level during the period of this experiment. However, trypsin activity was not significantly affected by the dietary protein content before 42 DAH, indicating a later onset of trypsin than amylase in the regulation of enzymatic synthesis induced by a dietary substrate.

Replacement of live prey by formulated diets in larval rearing of spider crab Maja brachydactyla

Preliminary experiments on the replacement in live prey by a formulated microbound diet (MBD) were carried out during larval development of the spider crab, Maja brachydactyla. Four levels (25, 50, 75 and 100%) of replacement of live prey (enriched Artemia metanauplii, EAM) were tested throughout larval development (zoea I = ZI, zoea II = ZII and megalopa = M). Replacement of up to 50% had no significant effect on the growth rate and survival of the larvae during any stage. Total replacement (100% MBD) resulted in a decrease in larval dry weight suggesting a poor assimilation of the proteins and lipids of the MBD. Survival of the larvae fed with the MBD did not appear to be affected, as it was significantly higher than the unfed control. Digestive enzyme activity (protease and amylase) of the larvae was probably influenced by both the physiological response to the formulated diet and larval ontogenetic changes. Further research is needed to improve MBD digestibility and to establish the lipid requirements of the larvae.

Interactive effect of two methyl-group sources on the growth and phospholipids’ content of kuruma shrimp Marsupenaeus japonicus Bate post-larvae

Six micro-bound diets were formulated to contain three levels of choline chloride (CC) (0.0, 0.6 and 1.2 g kg−1) and 2 levels of methionine (Met) (0 and 15 g kg−1). Soybean protein isolates (SPI) were used as the main protein source for its limited Met content. A significant (P < 0.05) interaction was determined between CC and Met on the survival (S %), weight gain (WG%), specific growth rate (SGR % day−1), feed efficiency ratio (FER), protein efficiency ratio (PER) and phosphatidylcholine (PC), phoshphatidylethanolamine (PE) and Met contents of the whole body of shrimp. The shrimp group did not receive either supplemental CC or Met showed lower (P < 0.05) values of the above-mentioned parameters than other shrimp groups fed with 0.6 and 1.2 g kg−1 supplemental CC with or without Met supplementation. The present study showed that supplementation of 1.2 g kg−1 CC in the diets could compensate shrimp post-larvae with the needed methyl group when received Met-deficient diets. The study also assumed that the biosynthesis of PC in the shrimp’s body can be achieved by the methylation of PE through the S-adenosylmethionine (SAM) pathway and/or through the cytosine di-phosphoryl (CDP) choline pathway directly from dietary choline.

Interactive effects of dietary vitamin C and phospholipid in micro-bound diet for growth, survival, and stress resistance of larval red sea bream, Pagrus major

This study was conducted to examine the effects of dietary ascorbic acid (AsA) and phospholipid (PL) and their interaction on growth, survival, and stress resistance in red sea bream larvae. Twenty-six days old red sea bream were fed nine micro-bound diets supplemented three levels of AsA (0, 800 and 1600 mg kg−1 diet) and PL (0, 20 and 40 g kg−1 diet) for 15 days. Dietary AsA and PL were both significant factors on survival rates. There was also an interaction between dietary AsA and PL on survival rate (P < 0.05). The larvae fed 800 or 1600 mg kg−1 AsA with 40 g kg−1 PL diets showed the highest survival rate, with values similar to those of the live-food supplemented group. Stress resistance against low salinity exposure significantly increased with increased dietary level of AsA and PL. However, significant interaction of AsA and PL was not detected. The larvae fed 1600 mg kg−1 AsA with 40 g kg−1 PL diet showed the highest stress resistance among all diets, but it was not significantly different than that of larvae fed 800 mg kg−1 AsA with 40 g kg−1 PL diet. This study clearly demonstrated that combined use of AsA and PL can improve survival of 26–40 days posthatching red sea bream larvae. Moreover, the present study suggested that 800 mg kg−1 AsA with 40 g kg−1 PL in diet was needed for producing high quality seedling under the stressful conditions.

Effects of Dietary Heat‐killed Lactobacillus plantarum on Larval and Post‐larval Kuruma Shrimp, Marsupenaeus japonicus Bate

Two feeding trials were conducted to evaluate the effects of heat‐killed Lactobacillus plantarum (HK‐LP) on larval and post‐larval kuruma shrimp, Marsupenaeus japonicus Bate. Five microbound diets were formulated to contain levels of a preparation containing 20% HK‐LP (HK‐LP Prep): 0, 0.001, 0.01, 0.1, and 1 g/kg. In the first experiment, zoea1 stage larvae were fed test diets for 8 d. Some parameters such as survival, developmental stage, metamorphosis to post‐larvae, and formalin stress resistance were evaluated. In second trial, post‐larval shrimp (16 ± 0.04 mg) were fed test diets for 30 d. Survival, body weight gain, specific growth rate, feed efficiency ratio, individual dry weight, total body length, osmotic and formalin stress resistances, and protease activity were evaluated. Results indicated that the larvae that received HK‐LP Prep at 0.1 and 1 g/kg diets showed significantly (P &lt; 0.05) higher survival than that of the control group. For the post‐larval trial, shrimp that received HK‐LP Prep at 1 g/kg diet were significantly higher than the control group in most of the growth parameters and stress resistance. However, shrimp that received HK‐LP Prep at 0.1 g/kg diet were significantly higher than the control group in survival only. For protease activity, there was no significant difference detected among groups.

Effects of Dietary Binders on Survival and Growth Performance of Postlarval Tongue Sole, Cynoglossus semilaevis (Günther)

Abstract A 30‐d feeding experiment was conducted in tanks to investigate the effects of four different binders (2% in microdiet) on the survival, growth performance, and specific activity of digestive enzymes in tongue sole, Cynoglossus semilaevis Günther, postlarvae (24 d after hatching, with initial average wet weight of 22.4 ± 6.65 mg [mean ± SD]). Five approximately isonitrogenous and isoenergetic microbound diets were formulated with carrageenan (Car), sodium carboxymethylcellulose (CMS), sodium alginate (SA), and gelatin (Gel) as binders, and a diet with no special binder as a control. A commercial diet (RQ Com., manufactured by Marubeni Nisshin Feed Co., Ltd., Chita, Japan) was used as another tested diet, and Artemia nauplii was used as live prey control. The results showed that the survival of the fish fed SA diet (31.3%) was significantly higher than that of fish fed CMS (21.8%), Car (10.8%), and control (21.8%) diets (P &lt; 0.05), but significantly lower than that of the fish fed the live prey (54.5%) diet (P &lt; 0.05). The results of growth followed the similar pattern as that of survival, although there were no significant differences in specific growth rate (SGR) among fish fed SA, CMS, Gel, the control, and RQ diets (7.2, 6.8, 7.0, 6.9, and 7.3% per day; P &gt; 0.05). However, fish fed Car diet had a significantly lower SGR (5.9% per day) than fish fed other diets. Percentages of secreted amylase in fish fed artificial diets were not significantly different, but fish fed artificial diets had significantly higher (P &lt; 0.05) secreted amylase than live prey group. Percentage of secreted trypsin in fish fed SA diet (54.9%) was relatively higher compared with other binders, and not significantly different from RQ Com. and live prey treatments. However, trypsin in fish fed Car diets (29.3%) was significantly lower than in other groups. Specific activities of alkaline phosphatase (AP) in the intestine and AP and leucine aminopeptidase N in brush border membranes in fish fed SA diet (264.6, 1882.8, and 187.2 mU/mg protein) were relatively higher compared with other binders. These results indicate that SA is one of suitable binders compared with carrageenan, CMS, and gelatin in microdiet of postlarval tongue sole.

Evaluation of four dietary protein sources for use in microbound diets fed to megalopae of the blue swimmer crab, Portunus pelagicus

Introduction of formulated diet particles for larval culture will simplify hatchery protocols and promote consistent survival, while decreasing total operating costs. The blue swimmer crab, Portunus pelagicus, is a commercially important species with substantial aquaculture potentials in the Indo-Pacific region. Feeding trials aimed at investigating protein nutrition of P. pelagicus larvae were undertaken with the megalopae instar. Microbound diets (MBD) with four different dietary protein sources (fish meal, squid meal, krill meal and soybean meal) were formulated and fed to newly molted megalopae until they metamorphosed to the first crab stage. Thirty megalopae were reared individually for each dietary treatment, with the addition of two control treatments of megalopae fed live Artemia nauplii and an unfed treatment. Survival was high for all fed treatments (73.3–93.3%), while total mortality was recorded for the unfed control. Megalopae fed the fish meal based MBD demonstrated higher survival than that of megalopea fed live Artemia, suggesting that MBD have the potential to completely replace live food for the culture of P. pelagicus megalopae without adversely affecting their survival. These results also suggest that P. pelagicus megalopae are able to adapt to a range of dietary protein sources. For megalopae fed live Artemia nauplii, mean development time was significantly shorter (4.0 ± 0.4 days) and the mean carapace width and dry weight of newly settled first stage crabs were significantly greater, (3.1 ± 0.0 mm, 1.3 ± 0.1 mg, respectively) than megalopae in all other fed treatments. Among MBD treatments, no significant difference in mean development time was detected, however, the mean carapace width of crabs that metamorphosed from megalopae fed fish meal based MBD (2.8 ± 0.0 mm) was larger than those fed squid meal based MBD (2.6 ±0.0 mm) and the mean dry weight of individuals fed fish meal based MBD (0.87 ± 0.04 mg) was also significantly heavier than those fed soybean meal based MBD (0.72 ± 0.04 mg). The outcome of this research provides valuable information regarding protein requirements of P. pelagicus megalopae and will aid in optimising formulated diet particles for potential use in commercial hatcheries.

Enzyme and acid treatment of fish meal for incorporation into formulated microbound diets for barramundi (Lates calcarifer) larvae

This study reports on two experiments in which the use of enzyme- and acid-treated fish meal were evaluated for incorporation into formulated microbound diets for barramundi (Lates calcarifer) larvae. In the first experiment, partially hydrolysed fish meal was used to determine whether partial hydrolysis increased the dietary value of fish meal used in microbound diets fed to L. calcarifer larvae. Total length and dry weight at the end of the experiment were both higher for larvae fed diets containing untreated fish meal than those fed diets containing any level of hydrolysate. Larval survival ranged from 15.8% to 47.2% but there were no significant differences between treatments (Fig. 3; P > 0.05). Carcass pepsin levels of larvae fed diets containing untreated fish meal were significantly higher than pepsin levels of larvae fed all other diets (P < 0.05). The second experiment determined the effects of incorporating graded levels of denatured fish meal (DF) into microbound diets for L. calcarifer larvae. Acid treatment increased the digestibility of fish meal approximately twofold when compared with intact fish meal. Larvae fed diets containing 45% DF had significantly higher total length and dry weight at the end of the growth trial than those fed a diet containing only intact fish meal. Larval survival ranged from 30.2% to 58.2%, with no significant differences between treatments. Whole homogenate pepsin levels were significantly affected by the level of dietary DF inclusion with larvae fed diets containing a greater proportion of intact fish meal containing higher pepsin levels. There was a significant correlation between dietary DF inclusion level and decreasing pepsin level (r2 = 0.569, P < 0.01); however, larval pepsin level did not correlate to either dry weight or total length (Pearson correlation, P > 0.05). The results of this study are a valuable contribution to our understanding of factors influencing the utilization of ingredients in microbound diets developed for marine fish larvae and will facilitate development of more effective formulated foods for them. Figure 3Open in figure viewerPowerPoint Mean (±SE) survival of barramundi larvae fed experimental diets containing fish meal hydrolysed for varying period (7.5–60 min), from 14 to 28 days after hatching. Means with different superscripts are significantly different (P < 0.05).

Chitosan as a wall material for a microencapsulated delivery system for Macrobrachium rosenbergii (de Man) larvae

Chitosan has been widely accepted as a wall material for preparing microcapsules of various purposes in human medicine. The possibility of using chitosan as a wall material for microencapsulating nutrients and drugs for aquaculture purposes, specifically to Macrobrachium rosenbergii larvae was evaluated in this study. Two types of chitosan-coated microcapsules were prepared using either acetone (MEC-A) or NaOH (MEC-N) as the cross-linking agents. They were compared with a microbound diet relative to total leaching of nutrients and free amino acids (FAA). Among the microcapsules, MEC-N showed the lowest level of total leaching of nutrients (23.3%) during 5 h of immersion in seawater and released 65% FAA after 60 min. During laboratory trials, 75% larvae had accepted the MEC-N capsule. The results of the study suggest that chitosan can be used as a wall material for preparing microcapsules to deliver drugs and nutrients to M. rosenbergii larvae.