Ontogeny of digestive enzymatic capacities in juvenile seahorses Hippocampus guttulatus fed on different live diets

Differences in survival and growth rates in seahorse Hippocampus guttulatus juveniles feeding on Artemia sp. or copepods have been related to specific digestive capacities of seahorse newborn, which are capable of actively forage on available prey from the first day of live. Other seahorse species, such as H. abdominalis and H. hippocampus, show high success feeding on Artemia nauplii suggesting species-specific differences in the digestibility of prey among seahorses. In this study, the profiles of digestive enzyme activity during the initial 15 days after release (DAR) were very low for trypsin, chitinase and α-amylase. In contrast, higher activities towards any of the assayed substrates for lipase (butyrate, octanoate and oleate) were evident from 0 DAR onwards. From 15 DAR onwards, the effect of diet composition became evident in juveniles previously fed on a mixed diet (Artemia + copepods), which showed a clear increase in all the assayed enzymes when compared with juveniles fed on Artemia as a sole prey. As a practical applicability of this study, a feeding schedule ensuring an adequate digestibility of the prey is proposed based on ontogenetic enzymatic activities of seahorse juveniles fed on different prey.     

Rearing the spotted seahorse Hippocampus kuda by feeding live and frozen copepods collected from shrimp ponds

This study evaluated the use of live and frozen copepods collected from shrimp ponds for rearing juveniles of the spotted seahorse Hippocampus kuda. Protein and HUFA contents in frozen copepods were all higher than in Artemia nauplii, the conventional live food for seahorse juveniles. The results of this study showed that copepods can be used as feed for rearing seahorse fry and juvenile. The spotted seahorse showed obvious preference for live copepods and rarely fed on dead copepods on the tank bottom. Furthermore, the combination of frozen copepods and live Artemia nauplii resulted in highest growth and highest survival of the experimental seahorses. Further research on possible effects of DHA:EPA ratio on survival and growth of young H. kuda is recommended.     

A Comparison of Growth,Survival, and Fatty Acid Composition of the Lined Seahorse,Hippocampus erectus,Juveniles Fed Enriched Artemia and a Calanoid Copepod,Schmackeria dubia

The purpose of this study was to evaluate the effect of varying dietary levels of highly unsaturated fatty acids (HUFAs) in live prey (Artemia nauplii and a calanoid copepod, Schmackeria dubia) on the growth performance, survival, and fatty acid composition of the lined seahorse, Hippocampus erectus, juveniles. Artemia nauplii were enriched with a commercial product (SS^? 50DE‐microcapsule as HUFA source, 2/3 DHA, 1/3 EPA. Shengsuo Fishery Feed Research Center of Shandong Province, Qingdao, China) at four concentrations of 0.0, 14.0, 28.0, and 56.0. Newly hatched juveniles were cultured for 35 days. The content of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and n‐3 HUFAs in the Artemia nauplii was positively related to the enrichment concentration. At the end of the trials, growth performance of the juveniles was positively related to the enrichment concentration as well. However, the juveniles fed prey enriched with the highest concentration of enrichment (56.0 μL/L) had the significantly lower (P < 0.05) survival rate. The juveniles fed the copepod had the best growth performance and the highest survival rate, suggesting that the copepod, S. dubia, is suitable for feeding the seahorse juveniles. The comparisons between the growth, survival, and fatty acid profiles of the juveniles fed Artemia and copepods indicate that the seahorse juveniles require dietary levels of DHA beyond those achieved by enriching prey with the HUFA enrichment. Surplus EPA resulted from an imbalance between DHA and EPA in the enriched Artemia nauplii probably caused an adverse effect on the seahorse juveniles. This study suggests that DHA and EPA requirement of the lined seahorse juveniles is roughly 32% of total fatty acid, and the optimal DHA/EPA ratio for the species is circa 4:1. To avoid an adverse effect resulting from excessive EPA, maximum proportion of EPA in enriched Artemia nauplii should not exceed 13% of total fatty acid, and a recommended minimum DHA/EPA ratio in the enriched Artemia nauplii is 1.46. Arachidonic acid (20:4n‐6) might not be an essential fatty acid for the seahorse juveniles.     

Live prey first feeding regimes for short‐snouted seahorse Hippocampus hippocampus (Linnaeus, 1758) juveniles

As with many species of seahorses, Hippocampus hippocampus wild populations are being subjected to uncontrolled exploitation in their natural environment. Thus, aquaculture could contribute to satisfy the commercial demand for animals while promoting the recovery of wild stocks. The present study was conducted to compare the effect of the substituting Artemia nauplii with rotifers for first feeding seahorse juveniles. Survival, growth and biochemical composition of prey organisms and fish were studied during the feeding trial. In addition, to help the biometric study, an anaesthetic test was also carried out using clove oil. The results showed excellent survival (average 60%) in juveniles exclusively fed with Artemia, with better values than those reported previously obtained by other authors for this species. By comparison, high mortality and poor growth were observed during first feeding with seahorses fed on rotifers. This could have been related to the lower energy intake and poorer nutritional value of the rotifers. Furthermore, clove oil concentrations of 25 ppm were found to work well as an anaesthetic for seahorse juveniles. Overall, first feeding Artemia alone was found to be an efficient and simplified method for feeding young H. hippocampus fry, building the principles for their culture for ornamental or re‐stocking purposes.     

Use of the microalga Nannochloropsis occulata in the rearing of newborn longsnout seahorse Hippocampus reidi (Syngnathidae) juveniles

The aim of this study was to evaluate the effect of microalgae on the rearing of newborn juveniles of the longsnout seahorse, Hippocampus reidi. Two treatments in three replicates were tested over a 15‐day period: with and without the addition of the microalgae Nannochloropsis oculata at a concentration of 2.02 ± 0.44 × 10⁶ cells mL^?1. At each replicate, beginning on the second day of life, 120 H. reidi juveniles (stocking density of 3 ind L^?1) were fed the offspring of the benthic copepod Tisbe biminiensis (100 copepod cm^?2) together with newly hatched Artemia nauplii (3.8 mL^?1). From the sixth day of life, enriched Artemia metanauplii replaced newly hatched Artemia nauplii. After 15 days, the H. reidi individuals were counted, measured and weighed. Mean survival was significantly greater in the microalgae treatment (76.42 ± 5.07%) than in the treatment with no microalgae (25.44 ± 6.91%). Moreover, total length, height and dry weight were significantly larger in the microalgae treatment. Thus, the addition of microalgae increases the growth and survival of H. reidi juveniles fed T. biminiensis and Artemia. The higher growth and survival of H. reidi juveniles was not related to the larger ingestion rates but probably to the nutritional improvement of the live feeds or to the probiotic effect. The protocol developed for rearing H. reidi juveniles resulted in a high survival, and represents an advance in the farming of this species.     

The impact of dietary supplementation with astaxanthin on egg quality and growth of long snout seahorse (Hippocampus guttulatus) juveniles

This study investigated the effect of dietary astaxanthin supplementation on egg quality and juvenile growth of long snout seahorse (Hippocampus guttulatus). Captive breed seahorse broodstock were fed four diets composed of frozen shrimp [Atlantic ditch shrimp, Palaemonetes varians) used as a vector to deliver artificial diets with increasing levels of astaxanthin (0, 75, 100 and 125 mg kg^?1 dry weight)]. The results indicated that the astaxanthin uptake into eggs from the enriched shrimp diets was highly efficient. Females fed unsupplemented astaxanthin diet produced similar‐sized eggs with lower concentration of astaxanthin than females fed diets with astaxanthin. The lower concentration of astaxanthin in the eggs was correlated with the production of smaller juveniles in comparison with the juveniles hatched from parents fed supplemented astaxanthin diets. Juvenile growth and survival was limited by their size on release from the male's pouch as at the end of 28‐day postparturition juveniles produced with the diet with no astaxanthin were still significantly smaller (P < 0.05) than those produced from parents fed astaxanthin‐supplemented diets. These results demonstrate a significant benefit of dietary astaxanthin supplementation in long snout seahorse diets in terms of improved egg quality and juvenile growth and survival.     

Effects of early weaning strategies on growth,survival and digestive enzyme activities in cobia (<Emphasis Type="Italic">Rachycentron canadum</Emphasis> L.) larvae

The effects of weaning strategies of cobia (Rachycentron canadum L.) larvae to commercial microdiets, either from rotifers or from Artemia, on growth, survival and enzymatic digestive capacity, were investigated. In the first experiment, cobia larvae were weaned from rotifers by co-feeding with a microdiet (Otohime) from 8, 13 or 20 days post-hatching (dph). The larvae in the control treatment were fed rotifers (2–12 dph), Artemia nauplii from 7 dph, and co-fed with the microdiet from 20 dph. In the second experiment, the larvae were weaned from Artemia, which was fed to the larvae from 7 dph, by co-feeding with a microdiet (NRD) from 8, 13 or 18 dph. The larvae in control treatment were fed rotifers, then Artemia to the end of the experiment (28 dph). Weaning of cobia larvae onto a microdiet directly from rotifers significantly reduced growth, survival and digestive capacity of the larvae and did not lead to larval acceptance of the microdiet, compared to those weaned from Artemia in the first experiment. Early weaning of cobia larvae onto NRD microdiet (on 8 or 13 dph) from Artemia in the second experiment also reduced growth, survival rate and gut maturation index, compared to those fed live feed. With available microdiets, weaning of cobia larvae could start from Artemia at around 18 dph in order to obtain comparable growth, survival and gut maturation to larvae fed live feed.     

Effect of photoperiod and tank colour on growth and survival of pelagic‐phase seahorse Hippocampus reidi

The effect of photoperiod and tank colour on the survival and growth of juvenile seahorse Hippocampus reidi was investigated in the first 15 days after release (DAR). In the first experiment, newly released seahorses were exposed to six photoperiods – 6 h of light (L):18 h of darkness (D), 10L:14D, 12L:12D, 14L:10D, 18L:6D and 24L:0D. In the second experiment, juveniles were kept in tanks of different background colours – blue, white, black, clear and red. No significant differences were observed in the growth and survival among seahorse subjected to 10–24 h of light (P > 0.05). At the end of 15 DAR, fish exposed to 6L:18D showed lower growth in height and weight compared to other treatments (13.8 mm vs. 20.0–22.2 mm and 13.4 mg vs. 37.2–43.2 mg respectively) and lower survival (80% vs. 88–95% respectively). Tank colour did not affect growth and survival of juveniles up to 15 DAR.     

The Effects of Different Feed Enrichments on Survivorship and Growth of Early Juvenile Longsnout Seahorse,Hippocampus reidi

Culturing the longsnout seahorse, Hippocampus reidi, remains challenging because unlike most cultured seahorse species, Artemia is not an optimal first feed. Ideally, more nutritious live feeds such as wild plankton or copepods should be used, but are not always readily available. Therefore, facilities commonly utilize enriched rotifers. Numerous feed enrichment products exist, including Dan's Feed Artemia Enrichment^®, (Dan's Feed) which is a blend of commercially available enrichment products. The aim of this study was to assess the survivorship, growth, and condition factor (CF) of 0–28 DPR (days post release) H. reidi fed with rotifers and Artemia enriched with Dan's Feed. This enrichment was evaluated against (1) rotifers and Artemia enriched with live alga (Isochrysis galbana), and (2) wild plankton and Artemia enriched with Dan's Feed. At 28 DPR, in terms of survivorship and growth, seahorses fed with rotifers and Artemia enriched with Dan's Feed had a lower CF and outperformed those fed rotifers and Artemia enriched with I. galbana. Seahorses fed with rotifers and Artemia enriched with Dan's Feed performed on par with those fed with wild plankton and Artemia with no significant difference in CF. These findings demonstrated that the culture of H. reidi may be feasible with rotifers and Artemia enriched with Dan's Feed .     

Early introduction of an inert diet and unenriched Artemia enhances growth and quality of Atlantic cod (Gadus morhua) larvae

The effects of two weaning diets and different weaning protocols on growth, survival, skeletal deformity and gut morphology of Atlantic cod larvae were studied in four groups from 16 to 45 days posthatch (dph). Cod larvae in groups 1 (early weaning with control diet) and 2 (early weaning with experimental diet) were used to evaluate the effects of different polar lipid content of weaning diets on larval and juvenile performance. Cod larvae in groups 2, 3 (early weaning with experimental diet + cofeeding with Artemia) and 4 (earlier weaning with experimental diet and earlier cofeeding with Artemia) were used to evaluate the effects of early introduction of dry diet and Artemia. From 45 to 170 dph, cod juveniles from all four groups were reared using a standard feeding protocol. No significant differences in growth, survival, deformities and gut morphology were found between cod larvae and juveniles from groups 1 and 2. Cod larvae fed on cofeeding regime with Artemia nauplii (groups 3 and 4) were bigger and had lower frequencies of jaw and neck deformities and higher foregut microvillus circumference than cod larvae from group 2. Our results demonstrate the importance of proper weaning protocols in producing better quality cod juveniles.     

A comparison of artificial and natural foods and their combinations in the rearing of goldfish, Carassius auratus (L.)

Intensive grow‐out of goldfish, Carassius auratus (L.), larvae and juveniles in closed systems requires the control of environmental conditions and feeding. This study investigates the use of different types of live food and combinations of live food and dry food in a series of four rearing experiments. Juvenile goldfish can be weaned from Artemia onto live food at about 24 days after the onset of feeding without causing a reduction in growth and survival. The replacement of Artemia by Daphnia at day 10 appears feasible, as growth and survival were not significantly affected. Fish fed decapsulated Artemia cysts grew better than fish fed live Artemia. Within the first 14 days, goldfish juveniles should be fed at least 155 cysts per fish per day to achieve fast growth and to minimize size variation.     

Effects of plant oligosaccharides derived from dragon fruit on growth,reproduction and survival of freshwater crustacean Daphnia magna

The freshwater crustacean Daphnia is widely used as live food for ornamental fish. To increase production, food supplementations are required when culturing Daphnia. Here, we aimed to clarify the effects of plant oligosaccharides derived from dragon fruit (DFO) on growth rate, egg production, number of first clutch juveniles and survival of Daphnia supplemented with five different concentrations of DFO, that is 0, 1, 3, 9, 27 mg/L. The results showed the growth and reproduction of Daphnia were enhanced when supplemented with DFO. Growth rate of Daphnia supplemented with 9 mg/L DFO was the highest among all treatments. The time that Daphnia produced the first clutch eggs was shorter in high concentration of DFO (3, 9, 27 mg/L). The number of juveniles in the first clutch increased in treatments of higher concentration of DFO (3, 9, 27 mg/L). These results suggest that plant oligosaccharides derived from dragon fruit increase growth and fecundity of Daphnia. Survival rates of Daphnia were 100% except for the treatment supplemented with 27 mg/L of DFO in which the survival rate was reduced to 87%. To our knowledge, this is the first functional evidence demonstrating that oligosaccharides derived from dragon fruit enhance growth and fecundity of Daphnia.     

The use of Pseudoalteromonas sp. F15 in larviculture of the Yesso scallop,Patinopecten yessoensis

A 49‐day rearing trial was conducted to investigate the effects of Pseudoalteromonas sp. F15 on growth, survival, digestive and immune‐related enzyme activities in larval and juvenile Yesso scallop, Patinopecten yessoensis. Larvae (Day 2 post‐fertilization) (d2 PF)) were provided with a diet only of microalgae (control) and supplemented with F15 at final concentrations of 1×10⁴ and 1×10⁶ cells/mL, respectively. Results indicated that the specific growth rates and survival rates of umbo larvae (d13 PF), crawling pediveliger larvae (d28 PF) and juveniles (d51 PF) fed the F15 supplementation diets at 10⁴ and/or 10⁶ cells/mL were significantly higher than those fed the diet of microalgae. Larvae and juveniles fed 10⁴ and/or 10⁶ cells/mL F15 supplementation diets showed a significant increase in pepsin, amylase and cellulase activities compared with the control group. The lysozyme, superoxide dismutase and catalase activities of larvae and juveniles fed the F15 supplementation diets at 10⁴ and/or 10⁶ cells/mL significantly increased compared to those fed the diet of microalgae. In addition, F15 protected juveniles against challenge with Vibrio splendidus. These data suggest that F15 can be useful in scallop larviculture.     

Mouth Growth and Prey Selection in Juveniles of the European Long‐snouted Seahorse,Hippocampus guttulatus

Seahorses are ambush predators that swallow the prey through their tubular snout. In order to better understand mouth growth and its effect on prey preference by juveniles of the seahorse Hippocampus guttulatus, experimental assays were carried out by feeding juveniles (0–30 – d after male's pouch release [dar]) on a mixture of rotifers, Brachionus plicatilis; Artemia nauplii; and copepods; Acartia tonsa. Mouth development in juveniles was accomplished by growth of upper and lower jaws, which were linearly correlated with juvenile length, whereas mouth width (MW) and height (MH) grew exponentially with juvenile size. Additionally, MW and MH were exponentially correlated, so that the transversal section of the mouth increased linearly with juvenile age and length. Gut content and Ivlev' selectivity index demonstrated a permanent rejection of rotifers for the whole experimental period and a clear preference of juveniles for copepods from 0 to 15 dar and for Artemia nauplii afterwards. Results also suggest that juveniles are able to ingest larger prey than those provided as the limiting factor in prey ingestion was not MW, as for many marine fish larvae, but mouth area. A tentative feeding schedule to successfully feed H. guttulatus juveniles from 0 to 30 dar is proposed.     

The performance of larval Seriola lalandi (Valenciennes, 1833) is affected by the taurine content of the Artemia on which they are fed

This study describes the effects of feeding taurine‐supplemented Artemia on the growth, survival, whole body taurine content and jaw malformation rate of larval yellowtail kingfish Seriola lalandi. Larvae were fed rotifers containing no supplemental taurine from 3 to 15 day post hatch (dph) and Artemia co‐enriched with taurine from 12 to 22 dph. Artemia were supplemented at concentrations of either 0, 0.8, 1.6, 2.4, 3.2 or 4.0 g of taurine L^?1 during the 18 h HUFA enrichment process. Taurine content in the Artemia increased from 0.76 ± 0.04% DW in those without supplementation to 3.95 ± 0.17% DW in those supplemented at 4.0 g L^?1. Survival rates of larval yellowtail kingfish were significantly lower in all taurine‐supplemented treatments compared to the unsupplemented control. Growth was significantly improved in those larvae fed taurine‐supplemented Artemia; however, we cannot attribute this improvement solely to taurine, as improved growth may have been a function of the reduced survival, and therefore increased prey availability, in these treatments. The whole body taurine content of larvae fed unsupplemented Artemia was significantly lower (1.85 ± 0.03% DW) than those fed supplemented Artemia, which did not differ from each other (pooled average 2.48 ± 0.03% DW), suggesting either a functional excretion mechanism is in place or that this represents the saturation value for larvae of this age. Jaw malformation rates were not affected by Artemia taurine content. The results of this research suggest yellowtail kingfish larvae may have a lower requirement and/or a reduced tolerance to excess dietary taurine than juveniles.     

Effects of the diet on seahorse (Hippocampus hippocampus) growth,body colour and biochemical composition

The short‐snouted seahorse (Hippocampus hippocampus) is a benthic fish that bases its survival on camouflage with the environment; therefore, both in wild and in captivity specimens, differences in coloration have been observed. This study was conducted to study the effect of five different diets, based on Artemia and frozen mysis, on fish survival, growth, skin colour parameters and biochemical composition. After 102 days of feeding different diets, no effect was observed on fish survival, growth, protein, ash or humidity content, except for colour changes on yellow and red fish. Differences on seahorse lipid and total carotenoids content were obtained in the experiment because of experimental diets. Fish eating Artemia showed the highest colour pattern response during the trial, with a maximum yellowness attained of 21. Additionally, a plateau of the skin colour expression for Artemia‐feeding fish was reached on day 180. A reversion of the yellowish skin colour was determined after a change of diet.     

Dietary organic acid salts mitigate plant protein induced inflammatory response and improve humoral immunity,antioxidative status and digestive enzyme activities in yellowfin seabream,Acanthopagrus latus

An eight‐week research was conducted to investigate the effects of single or combined administration of sodium propionate (Na‐P) and sodium acetate (Na‐A) on the performance of yellowfin seabream (Acanthopagrus latus) juveniles (6.5 ± 0.3 g). A plant protein (PP)‐rich diet was supplemented with sole or blends of organic acid salts (OAS) namely Na‐P and Na‐A to design six experimental feeds including control (without OAS), Na‐P5 (5 g/kg Na‐P), Na‐P10 (10 g/kg Na‐P), Na‐A5 (5 g/kg Na‐A), Na‐A10 (10 g/kg Na‐A) and Na‐P + A (5 g/kg Na‐P + 5 g/kg Na‐A). Except for Na‐A5 group, the other OAS‐supplemented treatments had higher growth and feed efficiency ratio than the control (p < .05). The inclusion of OAS in the experimental feeds pronouncedly enhanced plasma lysozyme and alternative complement pathway activities compared to the control. Furthermore, fish fed on the OAS‐supplemented diets had greater catalase and glutathione peroxidase activities in the liver than the control (p < .05). Total antioxidant capacity in the liver of fish fed on the OAS‐supplemented diet also was higher than the control. Fish fed on the OAS‐supplemented diets had higher pepsin, trypsin and lipase activities than the control. The insulin‐like growth factor 1 (IGF‐1) gene expression was remarkably down‐regulated in the liver of fish fed on the OAS‐supplemented diets compared to the control especially in groups fed on the Na‐P10 and Na‐A10 diets. The greatest IGF‐1 gene down‐regulation level in the gut was in fish fed on the Na‐P5 and Na‐P10 diets. The interleukine‐1β in the gut was remarkably up‐regulated in the control compared to the other groups (p < .05). The lactic acid bacterial colonies count in the gut of the control was lower than the OAS‐supplemented groups. Based on the findings of the present study, supplementing PP‐rich diets with 10 g/kg Na‐P or blends of Na‐P (5 g/kg) and Na‐A (5 g/kg) beneficially alleviated inflammatory responses and improved immune parameters and digestive capacity in yellowfin seabream juveniles.     

Rearing juvenile tench (Tinca tinca L.) under controlled conditions using Artemia nauplii as supplement to a dry diet

A 120-day experiment was performed with 4-month-old juvenile tench [initial mean weight: 0.31 g; total length (TL): 32 mm] to evaluate live Artemia nauplii as supplement to a dry diet for salmonids. All groups received the dry diet. Five treatments, differing in the amount of supplemented Artemia, were tested: without supplement, 450, 900, and 1,800 nauplii g⁻¹ initial fish biomass, and nauplii in excess. Groups that received Artemia supplement had significantly higher survival (between 89.4 and 98.7%) compared to those that received dry diet alone (49.2%), while among them there was no significant difference. Juvenile tench fed the dry diet supplemented with Artemia in excess had a specific growth rate (1.98), weight (3.40 g), and TL (63.90 mm) significantly higher than those in the rest of the treatments. The latter three features were not significantly different under limited co-feeding (450, 900, and 1,800 nauplii g⁻¹ biomass) averaging 1.26 specific growth rate, 1.40 g weight, and 48.50 mm TL. Tench fed the dry diet alone grew significantly less than the rest. Thus, the drawbacks of feeding juvenile tench with dry foods originally formulated for other fish species can be overcome by providing a supplement of Artemia nauplii.     

The administration of Lactobacillus plantarum directly to food: An effective way to improve the survival and growth of juvenile lined seahorses (Hippocampus erectus)

Previously, we found Lactobacillus plantarum had probiotic effects on lined seahorse (Hippocampus erectus) juveniles by the addition Lactobacillus directly into rearing seawater containing juveniles and their food (i.e. copepods). However, how the juveniles consumed Lactobacillus, directly from water or from copepods in whose guts Lactobacillus may have accumulated by ingestion, is still unclear. To clarify this, three experiments were successively carried out in this study. In the first experiment, the manner by which juveniles consumed Lactobacillus, namely, directly from food, was discovered via a 2 × 2 factorial design with two factors of water and food, and two levels with and without L. plantarum. In the second experiment, a 5 × 4 factorial design with five levels of L. plantarum doses (D: 5, 10, 20, 40 and 80 × 10⁸ cfu/L) and four levels of enrichment time (T: 0.5, 1.0, 1.5 and 2.0 hr) was conducted to analyse lactic acid bacteria (LAB) contents in the enriched copepods under different treatments. In the third experiment, six kinds of Lactobacillus‐enriched copepods chosen from the second experiment that carried significantly different LAB contents were fed to juveniles, and it was found that the copepods containing LAB greater than 5 log₁₀colonies/g had the most improved effects for survival and growth. In conclusion, the effective manner of L. plantarum administration in seahorses is by the addition to their food. Additionally, D40 * T1.0, whose LAB content was more than 5 log₁₀colonies/g, is generally the most economic copepod treatment for improving survival and growth in H. erectus rearing.     

Fructooligosaccharide supplementation in diets for tropical gar (Atractosteus tropicus) juvenile: Effects on morphophysiology and intestinal barrier function

Supplementary fructooligosaccharides (FOS) were evaluated on growth, survival, gut morphology, digestive enzyme activity and expression of intestinal barrier genes in tropical gar (Atractosteus tropicus). Four treatments were designed to include FOS (5, 10, 15 and 20 g/Kg) and were compared with a control (0 g/Kg) and the current commercial trout diet. Ten fish were stocked (0.25 ± 0.01 g and 4.2 ± 0.4 cm total length) per experimental unit by triplicate in a 45‐day experiment. Fish fed with 5 and 10 g/Kg of FOS had the highest average weight and total average length. Fish fed 5 g/Kg FOS showed the best growth indexes (absolute weight gain: 2.16; specific growth rate: 4.96; and feed conversion rate: 1.23) and survival (96.66%) and also had the highest acid protease, chymotrypsin and leucine aminopeptidase activities. Fish fed 5 g/Kg FOS had a high absorption area and accumulation of lipids in the liver. Finally, relative overexpression of occluding (occ), nucleotide‐binding oligomerization domain‐2 (nod2) and mucin 2 (muc2) was detected in fish fed 10 and 15 g/Kg FOS. The supplementation between 5 and 10 g/Kg FOS in diets for A. tropicus juveniles could be beneficial for growth, digestive enzyme activities, gut morphology and intestinal barrier function.