Growth Performance Of Juveniles Research Articles

Development of Limpet aquaculture: Advances on settlement and early growth of Patella aspera Röding, 1798

The limpet Patella aspera is an endemic species to the Macaronesian Islands. Its high economic value and vulnerability to exploitation has triggered the interest in the development of its aquaculture. Significant progress has been made in recent years, with the establishment of artificial fertilization and larval production protocols. However, there are at least two major challenges that need to be addressed before a commercial production can be achieved: larval settlement and juvenile grow-out. The aim of this research was to study the effect of different algae substrates (Ulvella lens, Amphora sp., Entomoneis sp., Navicula salinicola and Nitzschia sp.) on P. aspera settlement and to test the effect of two diets on juvenile growth: a mono diet based on U. lens versus a mixed diet composed by U. lens and the diatoms Nitzschia sp. and Navicula salinicola. Results showed that U. lens was the most efficient settlement cue, given that 84.6% of the post-larvae obtained were found on this algae substrate. In the following trial, U. lens was selected as the base diet for the grow-out phase. The rearing system used ensured juvenile survival percentages above 80%. The regular supply of the diatom mixture, as a dietary supplement, significantly enhanced juvenile growth performance. After 220 days post fertilization, limpets that grew on the mixed diet (U. lens plus diatoms) presented an average shell length of 19.280 ± 5.296 mm. Additionally, developed gonads were observed in females with less than 8 months. This study presents the first record of P. aspera juvenile grow-out, born from artificial fertilization, which represents a major step toward the development of limpet aquaculture.

Effect of Stocking Density and Diets Supplemented with Essential oils and or Probiotic on the Performance of Juveniles Nile tilapia (Oreochromis niloticus)

The present study was carried out to investigate the interactive effect of stocking density and diets supplemented with essential oils and or probiotic on the growth performance of juveniles Nile tilapia (Oreochromis niloticus), water quality parameters, intestinal morphology, and protection against Aeromonas hydrophila infection of Oreochromis niloticus. Total number of 640 O. niloticus fish (14.2 ± 0.95 g) were used in our work were allotted into eight groups with three replicates with two stocking densities (36 fish m-3 and 72 fish m-3) and four diets (control, Probiotic (Sanolife PRO-F®), Essential oils (EOs) blend (Super Immune®) and mix of Probiotic (Sanolife PRO-F®) and EOs blend (Super Immune®) respectively for 14 weeks and subsequently, challenged with A. hydrophila. The fish raised at the low stocking density exhibited increased weight gain, feed intake and specific growth rate compared with those raised at the high stocking density. Probiotic and/or EOs blend dietary supplementation improved Nile tilapia weight gain, daily gain, specific growth rate, total feed intake and feed conversion ratio. The water quality metrics' readings throughout the experiment all stayed within acceptable ranges for tilapia production despite the density increase. The fish raised at the low stocking density and received diet supplemented with mix of probiotic and EOs showed marked increased length of intestinal villi compared with the other groups. The EOs blend promoted better relative percent of survival with percentage of 100 % after challenge by A. hydrophila. It could be concluded that using EOs blend (Super Immune) and/or Probiotic (Sanolife PRO-F) as a dietary supplement for tilapia fingerlings would be a good choice due to their effective growth promoting, antibacterial effect and their positive impacts on fish intestinal morphology.

Comparison of live microalgae and Spray-dried algae powder effects on growth, digestive and antioxidant capacity of juvenile pearl oyster Pinctada maxima

The pearl production through the pearl oyster Pinctada maxima’s culture has developed slowly over the past decades due to over-fishing of wild populations and mass mortality at juvenile stages. Indoor farming is an alternative mode for P. maxima juvenile cultivation to improve survival rates. In pursuit of optimizing healthy management under the indoor farming mode, the objective of this investigation was to compare the growth performance, digestion, and antioxidant capacity of juveniles fed with different microalgae-based diets (live Isochrysis zhanjiangensis, Platymonas subcordiformis, Chaetoceros muelleri; and spray-dried I. zhanjiangensis, P. subcordiformis, C. muelleri powder). The juvenile survival rates fed with spray-dried microalgae powder (except C. muelleri powder) were not significantly different from those fed on live microalgae. However, the growth performance of juveniles fed with spray-dried microalgae powder could have been better than the live one. The digestive enzymatic activities were consistent with growth performance, and diets affected the antioxidant capacity. The spray-dried I. zhanjiangensis powder can serve as a substitute for live microalga in P. maxima juvenile indoor farming and is recommended under controlled conditions. The findings from this study would provide essential data to improve health management for P. maxima juveniles in indoor farming conditions.

The influence of in ovo feeding of black cumin extract on the physiological responses of broilers under hot tropical environments

An experiment was conducted to investigate the influence of in ovo feeding of black cumin extract (BC) on the intestinal morphology and physiological responses of broilers thermally challenged during incubation. The study involved the use of seven hundred Marshall broiler hatching eggs, which were assigned to 7 in ovo feeding treatments at embryonic day 17.5, as follows: eggs injected with 8 mg (EN), 6 mg (SN), 4 mg (FN), 2 mg (TN)BC, no in ovo feeding (NI), 0.9 % saline solution (SS), and 3 mg vitamin C (VC). Juvenile growth performance, plasma malondialdehyde (MDA), triiodothyronine (T3), superoxide dismutase (SOD), and haematological and serum biochemical indices were evaluated. The results revealed that the juvenile growth performance of SN birds was better than those of the NI, SS, FN and TN groups. The plasma SOD and T3 of the birds of SN and VC were significantly higher (p < 0.05) than the chickens of NI and SS treatments. The ileal crypt depth recorded in SN birds was lower (p < 0.05) compared to SS and NI values. To conclude, in ovo black cumin extract enhanced the gut health and lymphoid organs of broiler chickens with no pronounced effect on the thermotolerance of the birds at market age.

Optimization of Live Prey Enrichment Media for Rearing Juvenile Short-Snouted Seahorse, Hippocampus hippocampus

This study aimed to determine a nutritionally adequate feeding protocol for Hippocampus hippocampus juveniles. In the experimental trial, seahorses were fed copepods from 0–7 days post-parturition (DPP) and, from 8–28 DPP, four different dietary treatments: (copepods (control diet) (Cop); microalgae-enriched Artemia with a docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio of 2:1 (ArtDHA/EPA); microalgae-enriched Artemia with a DHA/EPA ratio of 2:1 along with 5% copepods (ArtDHA/EPA5%); and with 10% copepods (ArtDHA/EPA10%)). At the end of the trial, juvenile seahorses fed Cop grew significantly more (p < 0.05) (5.1 mg d−1) than those on fish-fed diets ArtDHA/EPA5% or ArtDHA/EPA10% (3.09 and 3.07 mg d−1, respectively), or those on the fish-fed ArtDHA/EPA (1.83 mg d−1) diet, all of which performed poorly. Data suggest that feeding copepods during the first 7 DPP promotes maturation of the digestive tract of juvenile seahorses, and the addition of a limited amount of copepods to the diet improves H. hippocampus juvenile growth performance when compared with the use of Artemia as a single diet due to the improvement of the essential fatty acid profile in the diets.

Effect of low crude protein breeder diets with balanced limiting amino acids on progeny chick quality and juvenile growth performance in Swarnadhara birds

A study was carried out to evaluate the effects of low crude protein diets supplemented with limiting amino acids on progeny chick quality and growth performance utilizing Swarnadhara laying hens. The feeding trial was done in 240 Swarnadhara layers from 29 to 40 weeks in a completely randomized design in five treatment groups with six replications of eight birds. The first treatment consisted of control diet (T1) based on corn soybean meal formulated at 16% CP and 2700 kcal ME meeting the ICAR (2013) requirements for CP and ME and also for the first four limiting amino acids at the following concentrations: methionine 0.35%, lysine 0.75%, threonine 0.52%, and tryptophan 0.16%. The other treatment diets (T2 to T5) were made isocaloric with control while reducing CP content to 15.5, 15, 14.5, and 14%, respectively, incorporating synthetic amino acids in sufficient quantities to match control amino acid levels. Chick quality was evaluated by grading chicks for appearance, activity and down conditions replicate-wise and individual chick hatch weights were recorded in 5 different breeder diet groups. The chicks in all the replicates were fed with the same basal diet containing 21% CP and 2800 kcal/kg ME as per ICAR (2013) requirements during first six weeks of age. The data on chick quality, body weight, feed consumption and feed efficiency showed no significant difference. Hence it can be concluded that the crude protein content of the Swarnadhara breeder diet could be reduced to 14% with essential amino acid supplementation without affecting the progeny performance.

Activation of the growth–IGF-1 axis, but not appetite, is related to high growth performance in juveniles of the Malabar grouper, Epinephelus malabaricus, under isosmotic condition

Salinity, a determining factor in aquatic environments, influences fish growth. Here, we evaluated the effect of salinity on osmoregulation and growth performance in juveniles of the Malabar grouper, Epinephelus malabaricus, a species of high commercial value in Asian markets; we also identified the salinity that maximized this species' growth rate. Fish were reared at 26 °C and under a 14:10 h photoperiod with a salinity of 5 psu, 11 psu, 22 psu, or 34 psu for 8 weeks. Change in salinity had minimal impact on the plasma Na+ and glucose concentrations, although the Na+/K+-ATPase (nkaα and nkaβ) transcript levels in the gills were significantly lower among fish reared at 11 psu salinity. Concomitantly, oxygen consumption was low in fish reared at 11 psu salinity. The feed conversion ratio (FCR) was lower in fish reared at 5 psu and 11 psu salinities than at 22 psu and 34 psu salinities. However, the specific growth rate (SGR) was higher in fish reared at 11 psu salinity. These results suggest that rearing fish at 11 psu salinity would decrease energy consumption for respiration and improve food-conversion efficiency. Among fish reared at 11 psu salinity, the transcript levels of growth hormone (gh) in the pituitary, as well as its receptor (ghr) and insulin-like growth factor I (igf-1) in the liver, were upregulated; these findings suggested stimulation of the growth axis at low salinity. In contrast, there were minimal differences in the transcript levels of neuropeptide Y (npy) and pro-opiomelanocortin (pomc) in the brains of fish reared at any salinity, suggesting that salinity does not affect appetite. Therefore, growth performance is higher in fish reared at 11 psu salinity because of activation of the GH-IGF system, but not appetite, in Malabar grouper juveniles.

Embryonic exposure to environmentally relevant levels of tributyltin affects embryonic tributyltin bioaccumulation and the physiological responses of juveniles in cuttlefish (Sepia pharaonis)

Tributyltin (TBT) is a typical organic pollutant that persists in aquatic sediments due to its wide usage as an antifouling fungicide during the past few decades. Despite increased awareness of the serious negative consequences of TBT on aquatic species, studies on the effects of TBT exposure on cephalopod embryonic development and juvenile physiological performance are scarce. To investigate the lasting effects of TBT toxicity on Sepia pharaonis from embryo to hatchling, embryos (gastrula stage, 3–5 h post fertilization) were exposed to four levels of TBT until hatching: 0 (control), 30 (environmental level), 60, and 120 ng/L. Subsequently, juvenile growth performance endpoints and behavioral alterations were assessed over 15 days post-hatching. Egg hatchability was significantly reduced and embryonic development (i.e., premature hatching) was accelerated in response to 30 ng/L TBT exposure. Meanwhile, TBT-induced alterations in embryonic morphology primarily included yolk-sac lysis, embryonic malformations, and uneven pigment distributions. During the pre-middle stage of embryonic development, the eggshell serves as an effective barrier to safeguard the embryo from exposure to 30–60 ng/L TBT, according to patterns of TBT accumulation and distribution in the egg compartment. However, even environmental relevant levels of TBT (30 ng/L) exposure during embryonic development had a negative impact on juvenile behavior and growth, including slowing growth, shortening eating times, causing more irregular movements, and increasing inking times. These findings indicate that after TBT exposure, negative long-lasting effects on S. pharaonis development from embryo to hatchling persist, suggesting that long-lasting toxic effects endure from S. pharaonis embryos to hatchlings.

Study on Juvenile Growth Performance of Non-Descript Country Chicken Under Intensive System of Management in Puducherry

Study on Juvenile Growth Performance of Non-Descript Country Chicken Under Intensive System of Management in Puducherry

Optimum dietary calcium requirement of Hypophthalmichthys molitrix juveniles

A 13-week feeding trial was conducted to determine the optimum dietary calcium (Ca) requirement of juvenile silver carp, Hypophthalmichthys molitrix (3.20 ± 0.02 g). For this, five isonitrogenous semipurified diets containing 2.3, 5.3, 8.3, 11.1 and 14.2 g/kg Ca levels were formulated. The growth performance of juveniles was significantly affected by Ca supplementation with the maximum increase recorded at 8.3 g/kg Ca and stabilized thereafter (p < 0.05). Whole-body protein and ash contents were increased (p < 0.05) with increased dietary Ca up to 8.3 g/kg and then levelled off (p < 0.05). However, the moisture and fat contents in whole body were decreased (p < 0.05) with the increased Ca supplementation up to 8.3 g/kg and plateaued thereafter. Calcium and P concentration showed an increasing trend (p < 0.05) with the increasing Ca level up to 11.1 g/kg in whole body and 8.3 g/kg in bones and scales. However, Mg and Zn concentrations were decreased (p < 0.05) with increasing dietary Ca levels. The highest alkaline phosphatase (ALP) activity (p < 0.05) was recorded in the fish-fed diet containing 11.1 g/kg Ca diet; however, serum Ca, P and Ca/P ratio remained unaffected (p > 0.05). Broken line regression showed that 8.45 g/kg Ca is the optimal requirement for the growth of silver carp. Conclusively, an increase in Ca supplementation up to 8.3 g/kg significantly improved the overall performance of silver carp without urging the negative effects.

Short initial period of high carbohydrate feeding improves nutrient utilisation in juvenile Nile tilapia (Oreochromis niloticus) fed a high carbohydrate diet

The objective of this study was to investigate the effects of different durations of early carbohydrate (CHO) feeding stimulus on the growth performance and CHO metabolism of Nile tilapia later in life. The first-feeding nutritional stimulus treatments were a low-CHO/high-protein diet for 3 weeks (control group), a short duration high-CHO/low-protein (HC/LP) diet for 1 week (short-HC/LP group), and a long duration HC/LP diet for 3 weeks (long-HC/LP group). As expected, compared to the control fry, the short- and long-HC/LP diets were associated with lower growth performance in the fry at the end of the stimulus period, which was associated with differential gene expression for protein and glucose metabolism, followed by compensatory growth later. Subsequently, to test the existence of CHO metabolic programming, juvenile fish were challenged with a high-CHO diet in weeks 21–24. Our results show that early HC/LP stimulus improved the growth performance of juveniles, suggesting that a history of early HC/LP stimulus contributes to better use of dietary CHO for growth. Interestingly, metabolism modifications linked to early HC/LP stimulus were observed in many of the parameters, irrespective of the duration of early stimulus. The upregulation of the glucose gene (involved in glycolysis and transport) in juveniles that experienced early stimulus and the downregulation of genes involved in gluconeogenesis and amino acid catabolism can explain the improved use of the CHO diet in these fish. Taken together, early HC/LP feeding in tilapia fry is associated with highly significant metabolic programming later in life. Moreover, because the long-HC/LP treatment had stronger direct negative effects on growth performance than the short-HC/LP treatment, this study suggests that a 1-week early HC/LP feeding period could be sufficient to program juvenile tilapia for better nutrient use.

First linkage maps and a pilot QTL analysis for early growth performance in common dentex (Dentex dentex) and sharpsnout seabream (Diplodus puntazzo)

Two potential candidate species for the Mediterranean aquaculture–the common dentex (Dentex dentex) and the sharpsnout seabream (Diplodus puntazzo)-are used in the present study in order to depict their genetic architecture for the first time. We have constructed the first linkage maps for both species using SNP markers derived from ddRAD sequencing. The quality of the maps produced was verified from comparative analysis with the most studied and phylogenetically related sparid species, the gilthead sea bream (Sparus aurata). A high genetic similarity was detected, based on the high number of alignments of the two new species against the reference genome of the gilthead seabream. Furthermore, a pilot study for QTL analysis per species was performed using phenotypic measurements at the juvenile stage (approximately 2 g) and revealed putative genomic areas which affect juvenile growth performance. One of those areas was located close to a candidate gene (ANGPTL6 gene) which affects growth performance. The present study improves our knowledge on the genetic architecture of those two species by presenting not only the first linkage maps, but also by providing some indications for growth performance QTL. The results can be used as a starting point to initiate further research for the genetic improvement of these two new species.

Importance of experienced thermal history: Effect of acclimation temperatures on the high-temperature tolerance and growth performance of juvenile marbled flounder.

Experienced thermal history often affects the temperature tolerance of fish; however, the effect of thermal history on growth performance is unclear. To contribute to effective stocking (release of hatchery-reared juveniles in the field), we conducted four laboratory experiments using juvenile marbled flounder (Pseudopleuronectes yokohamae, around 30mm standard length and 0.3g body wet weight) acclimated at 12°C and 24°C for approximately 2 weeks to investigate the effects of acclimation temperature on high-temperature tolerance, food consumption, and growth performance. The acclimation to 24°C increased tolerance to high temperatures, as shown in a 24-h exposure experiment and in a temperature elevation experiment. The 50% lethal temperature (upper incipient lethal temperature) was estimated to be 25.9°C and 29.0°C for the 12°C and 24°C acclimation groups, respectively. In subsequent experiments, we tested the effects of high and low temperature acclimation on the food consumption and growth performance of two size groups of juveniles (28.7±2.0 and 34.5±2.9mm, mean±SD), that were reared at temperatures ranging from 14°C to 23°C. The optimal temperature for growth was 20°C and did not differ between the acclimation temperatures or between the size groups. However, food consumption and growth performance were suppressed by acute temperature changes. Specifically, feeding and growth were lower in the 24°C-acclimated group than in the 12°C-acclimated group when exposed to 14°C, which is close to the natural water temperature at release in the field. These results suggest that experienced thermal history does not affect the optimal temperature but can affect the growth performance of juveniles. To maximize the post-release growth of hatchery-reared juveniles, the influence of thermal history should be taken into consideration and acute thermal changes before release should be avoided.

Growth, Development, and Survival of Portunus pelagicus Larvae and Juveniles in Different Feed Regimens, Rearing Media, and Stocking Densities

Various factors in P. pelagicus seed production and grow-out culture were investigated in this study. Experiments were conducted to 1) compare natural and artificial feeds for larval production, 2) evaluate indoor tank and outdoor net cages as rearing media, and 3) assess different stocking densities for grow-out culture. Growth, development, and survival were assessed for the performance of each variable. (I) In larval production, the development of megalopa larvae into crab instar was synchronous in both natural and artificial feed treatments in a 5-day rearing observation. Crab instars began to appear on Day 4 with 27% composition in both feeds. Although survival appeared to be relatively higher in natural feed (43.96 ± 6.04%), this was not significant from survival in artificial feed treatment (33.33 ± 13.34), (t = 0.726, p &gt; 0.05). (II) In Phase I growout culture, a two-variable design experiment was conducted to assess growth performance and survival of crab juveniles reared in indoor tanks and outdoor net cages at different stocking densities. Specific growth rate (SGR) differed significantly (t = 2.937, p &lt; 0.05) between indoor tanks (6.39 ± 0.24%.d-1) and outdoor net cages (8.31 ± 1.11%.d-1). However, mean survival rate was better in indoor tanks (20.83 ± 9.24%) than outdoor net cages (8.94 ± 3.58% only), (t = 2.938, p = 0.015). In terms of stocking density, SGR was highest in 75 ind.m-2 (7.87 ± 2.44%.d-1). However, growth performance and survival of juveniles among different stocking densities were not significantly different (p &gt; 0.05). Furthermore, two-factor ANOVA results have shown that growth performance of the juveniles was influenced by both the differences in rearing medium and stocking density, but not in terms of survival (F = 0.120, p = 0.888). (III) In Phase II grow-out culture, juveniles attained highest SGR (3.54 ± 0.56%.d-1) at 5 ind.m-2 stocking density. This was followed by 15 ind.m-2 (3.45 ± 2.39%.d-1) and by 10 ind.m-2 (2.33 ± 0.50%.d-1) (p &gt; 0.05). However, survival rate was highest in 15 ind.m-2 (46.67 ± 0.00%), but the differences among other stocking densities were not statistically significant (p &gt; 0.05). Overall, results suggest that artificial feed can be an alternative for Artemia in rearing megalopae to crab instar stage. Stocking density in Phase I and II grow-out culture did not substantially affect growth performance and survival of juvenile P. pelagicus. However, higher stocking density increases incidence of cannibalism among reared crabs.

Evaluation of growth performance of half sib progenies of Toona ciliata M. Roem under field conditions

The study was conducted to evaluate the juvenile growth performance of half sib progenies of twenty four genotypes of Toona ciliata M. Roem under field conditions of Punjab, India. Seed source (S3) Ludhiana exhibited outstanding performance for growth parameters. Among genotypes progenies of S3G7 (Ludhiana), S3G8 (Ludhiana), S1G1 (Talwara) and S2G4 (Kamahi Devi) were found to be most promising for growth traits. The phenotypic coefficient of variation values were observed higher for all the parameters than genotypic coefficient of variation. Moderate heritability and genetic gain was observed for branch angle and plant height. Highly significant and positive genotypic and phenotypic correlations were observed for plant height with collar diameter and stem straightness and collar diameter with number of branches per plant. The genotypes were clustered into three distinct groups with maximum diversity of (30.68) between clusters I and cluster III and can be utilized for future heterotic breeding.

Fish oil-free diets for Pacific white shrimp Litopenaeus vannamei: The effects of DHA-EPA supplementation on juvenile growth performance and muscle fatty acid profile

The influence of a combination of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in fish oil free diets were evaluated on the overall performance of Litopenaeus vannamei. Within this purpose, four isoproteic (approximately 410 g kg−1 of crude protein) and isolipidic diets were manufactured to contain 85 g kg−1 of lipids provide from beef tallow, soybean oil, and the fat contained in the ingredients, supplemented at four levels of DHA-Nature™; 0, 1, 1.7, and 2.4 g kg−1 (containing 240 and 70 g kg−1 DHA and EPA), corresponding to: Control; low, L-DHA; medium, M-DHA; and high, H-DHA. The diets resulted with the final DHA concentration of 10.7 (Control); 13.1 (L-DHA); 17.0 (M-DHA); and 23.7 mg g−1 lipid (H-DHA). Twenty-five L. vannamei juveniles (8.63 ± 0.08 g) were randomly divided into 12 tanks (500-L; in triplicate) fed to satiation four times a day, approximately to a 6% of the total biomass. After seven weeks of experimentation, it was revealed that H-DHA treatment, significantly favored the growth performance compared to the Control. In general, the muscle fatty acids (FA) reflects the diet composition, with significantly higher DHA deposition, in animals fed the H-DHA diet (23.7 mg g−1 lipids of DHA), in comparison with L-DHA and M-DHA diets (13.1 and 17.0 mg g−1 lipids, respectively). The results pointed out preferential oxidation of L. vannamei by FA included in high concentrations in the experimental diets such as 18:1n-9 and 18:2n-6, those of most representative FA in beef tallow and soybean oil composition, respectively. Inversely, it was observed an accumulation of essential long-chain polyunsaturated fatty acids (LC-PUFA), especially EPA and DHA even at low levels of FA inclusion.

Long-chain PUFA profiles in parental diets induce long-term effects on growth, fatty acid profiles, expression of fatty acid desaturase 2 and selected immune system-related genes in the offspring of gilthead seabream

The present study investigated the effects of nutritional programming through parental feeding on offspring performance and expression of selected genes related to stress resistance in a marine teleost. Gilthead seabream broodstock were fed diets containing various fish oil (FO)/vegetable oil ratios to determine their effects on offspring performance along embryogenesis, larval development and juvenile on-growing periods. Increased substitution of dietary FO by linseed oil (LO) up to 80 % LO significantly reduced the total number of eggs produced by kg per female per spawn. Moreover, at 30 d after hatching, parental feeding with increasing LO up to 80 % led to up-regulation of the fatty acyl desaturase 2 gene (fads2) that was correlated with the increase in conversion rates of related PUFA. Besides, cyclo-oxygenase 2 (cox2) and TNF-α (tnf-α) gene expression was also up-regulated by the increase in LO in broodstock diets up to 60 or 80 %, respectively. When 4-month-old offspring were challenged with diets having different levels of FO, the lowest growth was found in juveniles from broodstock fed 100 % FO. An increase in LO levels in the broodstock diet up to 60LO raised LC-PUFA levels in the juveniles, regardless of the juvenile's diet. The results showed that it is possible to nutritionally programme gilthead seabream offspring through the modification of the fatty acid profiles of parental diets to improve the growth performance of juveniles fed low FO diets, inducing long-term changes in PUFA metabolism with up-regulation of fads2 expression. The present study provided the first pieces of evidence of the up-regulation of immune system-related genes in the offspring of parents fed increased FO replacement by LO.

Disentangling the role of climate and soil on tree growth and its interaction with seed origin

When considering options for adapting forests under climate change, climate is treated as the dominant driver of forest growth, while soil properties are often ignored mainly due to shortage of accurate data. The effects of climate and soil on forest growth may vary due to local adaptation to both climate and soil, and these local adaptations might need to be considered when transferring seed provenances under climate change.Data from 29 provenance trials of Norway spruce (Picea abies (L.) Karst.) across a wide gradient of planting conditions in Austria was used to develop Structural Equation Models (SEMs) to quantified the role of climatic and soil drivers and their interactions on juvenile growth performance and to test if provenance origin affects the relative importance of these drivers.Climate and soil of the planting site location were found to have similar direct effects on juvenile tree growth, however, climate was found to be more important because of additional indirect effects via interactions with soil parameters. Notably, the relative effects of climate and soil vary among different provenance groups. Climate constraints are dominant for seed sources originating from colder and/or high altitude locations, while test site climate and soil are equally important contributors of growth for provenances originating from warmer origin and lower elevation sites. Together with the better growth performance of the latter provenance group their plasticity allows them to utilize a wide range of soil conditions.

Effects of intermittent feeding on water quality, skin parasites, feed consumption, and growth performance of juvenile longfin yellowtailSeriola rivoliana(Valenciennes, 1833)

This study investigated the effect of intermittent feeding on the water quality, occurrence of skin parasites, feed consumption, and growth performance of juveniles (102.7 ± 5.1 g) longfin yellowtail, Seriola rivoliana. Fish were exposed for 89 days to six different feeding regimes: continuous daily feeding fed one or twice a day (treatment 24R1 and 24R2); 2‐day fasting and refed once or twice a day for 1 day (treatment 48R1 and 48R2); and 3‐day fasting and refed once or twice a day for 1 day (treatment 96R1 and 96R2). Water quality was not affected by feeding strategies. Likewise, condition factor was not affected by fasting up 48 hr. On the other hand, lowest survival in 96R1 was not related with abundance of skin parasites (Neobenedenia girellae). Specific growth rate, feed intake, feed efficiency, and morphological indices were not statistically different (p > 0.05) between 2 days fasted fish and continuously fed fish. Partial compensatory growth in 48R2 could be attributed to a hyperphagic consumption (8.2 ± 1.1 g day⁻¹ fish⁻¹) and feed conversion efficiency (0.61 ± 0.03). A feeding strategy based on cyclical 48 hr of starvation followed by 1 day of refeeding twice may be used for on‐growing juvenile longfin yellowtail without reduction in growth or welfare of fish.

Growth, biochemical, fatty acid composition, and mRNA levels of hepatic enzymes in genetically improved farmed tilapia (GIFT,Oreochromis niloticus) (Linnaeus, 1758) at different stocking densities

Investigated were the effects of stocking density on juvenile growth performance, serum biochemistry, fatty acid composition, and mRNA levels of enzymes involved in lipid metabolism in genetically improved farmed tilapia (GIFT), Oreochromis niloticus. Juvenile fish (n = 900) were distributed into 15 tanks at five initial stocking densities (75, 150, 225, 300, and 375 g/m3 per 800-L tank, represented as D1–D5, respectively). Temperature was maintained at 28 ± 0.3°C, and water flow rate into the tanks was about 8 L/min. The fish accepted floating pelleted feed (crude protein 28%, crude lipid 6%, and gross energy 149.2 KJ/g diet). The feed amount offered was 4%–8% of body weight. At the end of the 60-day experiment, the final stocking densities were 1,454.18, 2,010.60, 2,913.13, 3,819.73, and 4,380.80 g/m3, respectively. Growth and body mass coefficient of variation were significantly affected (p < .05). No differences in feed conversion rate or survival were found (p > .05). Muscle lipid contents decreased with stocking density from D1 to D5. Serum total protein and cholesterol levels were not affected by the stocking density but the D5 group produced the highest serum cortisol and lactate levels and the lowest glucose levels compared to those of the other groups. Lower muscle saturated fatty acid and n−3 polyunsaturated fatty acid contents were observed in the D4 group than in the other groups, whereas the reverse was found in the n−6 polyunsaturated fatty acid content. Hepatic glucose 6-phosphate dehydrogenase, fatty acid synthetase, hormone-sensitive triglyceride lipase, and lipoprotein lipase mRNA levels were significantly upregulated in response to a high density. These data suggest that the GIFT adapted to high-density conditions by altering the composition of muscle fatty acid and stimulating lipid metabolic enzymes. These mechanisms may help fish respond to high stocking density stress in intensive aquaculture systems.