EAS 2016 Meeting Poster Presentation

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Nutritional stimuli of gilthead seabream (Sparus aurata) larvae by dietary fatty acids

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The concept of nutritional programming raises the interesting possibility of directing specific metabolic pathways or functions in juvenile fish, for example, to improve the use of substitutes to fishmeal and oil, and hence to promote sustainability in aquaculture. The aim of the study was to determine effects of early nutritional stimuli of gilthead seabream larvae and check if nutritional programming of gilthead sea bream is possible between 16 days post hatching (dph) and 26 dph. A trial was conducted to determine the effects of early nutritional stimuli of gilthead seabream larvae. Five experimental microdiets (pellet size <250 μm) were formulated containing five different proportions of a marine lipid source rich in long-chain polyunsaturated fatty acids (LC-PUFA) and two vegetable lipid sources rich in linolenic and linoleic acids. The results of this study demonstrate that dietary n-3 LC-PUFA levels increased larval growth and survival affecting Δ6 desaturase gen (fads2) expression and retinal neurons density. However, the high mortalities obtained along on-growing in fish fed low n-3 LC-PUFA at 16 dph constrained the feasibility of nutritional programming of gilthead seabream during this late developmental window and needs to be further investigated.

Link to full article: http://onlinelibrary.wiley.com/doi/10.1111/are.12874/abstract


Parent diets effect utilization of different lipids on the progeny

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The complete removal of fishmeal (FM) and fish oil (FO) is required to promote the sustainable development of aquaculture and for that, fast growing high quality fish that are fed without FM and FO are necessary. Early nutritional programming may allow the production of fish better adapted to utilize diets with vegetable meals (VM) and oils (VO). The main objective of this study was to research in the potential value of fatty acids as modulators of early nutritional programming in marine fish for a better utilization of VO/VM. For that purpose gilthead sea bream (Sparus aurata) broodstock were fed four different replacement levels of FO by linseed oil (LO) and their effect on fecundity and spawn quality, egg composition, Δ-6-desaturase (Δ6D) gene expression, progeny growth performance and their growth response to a challenge with diets low in FO and FM, but high in VO and VM. The results showed that feeding gilthead sea bream broodstock with high LO diets had very long-term effects on the progeny. Thus, FO replacement by LO up to 80–100% in broodstock diets for gilthead sea bream not only reduced fecundity and spawn quality, but also growth of 45 dah and 4-month-old juveniles, as well as Δ6D gene expression. However, when the 4 month-old juveniles were fed with a low FM and FO diet, even those from broodstock fed only 60% replacement of FO by LO showed a higher growth and feed utilization than juveniles from parents fed FO. These results demonstrate the interesting potential of early nutritional programming of marine fish by broodstock feeding to improve long-term performance of the progeny. Further studies are being conducted to determine optimum nutrient levels in the broodstock diets and the molecular mechanisms implied to develop effective nutritional intervention strategies for this species.

Statement of relevance

This study demonstrates for the first time in fish the potential of broodstock nutrition to conduct early nutritional programming of culture fish for a better utilization of low fish meal and fish oil diets by the progeny, showing its effect not only during reproduction and larval development but also during on-growing.

 Link to article: http://www.sciencedirect.com/science/article/pii/S0044848615001908

Long time effects of parent’s diet and “reminder” programming effect of 16 month juveniles

Presented as a poster in Epiconcept Cost Action’s workshop Periconception Environment

26-29 April 2015, Dubrovnik, Croatia

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Nutritional programming is widely studied in vertebrates and it has been shown that nutritional stimuli during developmental stages may trigger short or/and longterm effects on several physiological functions of the organism. Studies about nutritional programming on different fish species also showed that functioning of certain metabolic pathways involved in lipid and carbohydrate metabolism of juveniles may be influenced by an early diet. Our research on sea bream revealed that nutritional programming through broodstock nutrition is very effective and improves the ability of 4 month juveniles to use vegetable oils (VO) and vegetable meals (VM). However, it is still unknown longer term effects of this type of programming. The present study examined the longterm influences of programming through broodstock nutrition in 16 month juveniles. Therefore, sea bream broodstock were fed four different replacement levels of fish oil (FO) by VO. FO replacement by VO affected growth of 45 day and 4 month-old juveniles, as well as Δ6 desaturase gene expression. Besides, when 4 month-old juveniles were fed with a VO-VM based diet, fish from broodstock fed VOs utilized more effectively this diet and showed a higher growth. Afterwards, all fish were fed with a standard fishmeal/FO based commercial diet for 16 months. Then, fish were challenged with a VM/VO based diets for 2 months. The results showed that the influence of parental feeding had disappeared on 16 month-old fish. However, those fish that were challenged at 4th month with a VM-VO based diet significantly showed the effect of parental feeding, suggesting that the nutritional challenge at 4 months may acted as a “reminder” effect added of the parental programming. Furthermore, long effects of nutritional programing and a remainder diet on fatty acids and gene expression involved in lipid metabolism were studied. Grant support:European Commission Directorate for Research & Innovation Grant A KBBE-2001-5-288925 (ARRAINA)

Meeting’s web page

Nutritional reprogramming in fish: Importance of developmental windows

Presented in Epiconcept Cost Action’s workshop Epigenomic Toolbox: from Methods to Models.

07-09 May 2014, Las Palmas, Spain

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Studies in mammals and humans show that dietary influences exerted at critical developmental stages early in life (neonatal nutrition, post-natal nutrition) may have long-term consequences on physiological functions in later life. Nutritional programming phenomenon is largely studied in mammalian models for the understanding of diseases such as the metabolic syndrome or diabetes. The functioning of certain metabolic pathways such as fatty acid metabolism in juvenile fish also depends on specific nutritional signals during the critical larval periods, demonstrating that the concept of metabolic programming also exists in fish. Modulation of key enzymes for fatty acid synthesis is possible by feed given to juveniles. The present study will examine the influences early nutritional programming either during embryonic phase or during metamorphosis. To affect nutrient intake during these two periods either broodstock or early weaning diets were modified and their effects studied on sea bream performance, lipid metabolism, gene expression and response after a feeding challenge. Specific genes such as those involved in essential fatty acids metabolism, were markedly affected by the nutritional programing at both developmental windows. For instance an up regulation of delta-6 desaturase gene expression was obtained when fish was conditioned with moderate levels of vegetable oils, whereas extreme conditioning conditions inhibited the expression. Despite it was potentially possible to condition fish during metamorphosis, the larvae were very sensitive during this period and high mortalities occurred during the treatment. When fishes were programmed through broodstock nutrition, a very high survival rate was obtained. Even extreme conditioning produced reliabe survival rates. After treatment with different conditioning during the embryonic period, all fish were fed standard fishmeal diet for three months and, afterwards, challenged with vegetable oils. A significant positive effect of the nutritional programming was observed in lipid metabolism response as well as a better utilization of the feeds. Grant support: European Commission, Directorate for Research & Innovation, Grant Agreement KBBE-2001-5-288925 (ARRAINA)

Meeting’s web page

Growth response of European sea bass under different starvation cycles and feeding rates

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The compensatory growth response of the European sea bass (Dicentrarchus labrax) faced cycling starvation and restricted ration was assessed. Juveniles (10.5 g) were stocked into 15 tanks at a density of 25 fish per tank. Five different feeding regimes were tested on triplicate groups of fish: CSatiation: control fed for 60 days without deprivation, CRestricted: 25% restricted feeding, S-R: 1 day starvation then 4 days CRestricted feeding, R-F: 1 day CRestricted feeding then 4 days CSatiation feeding, and, finally, S-F: 1 day starvation then 4 days CSatiation feeding. The specific growth rate of fish in the CSatiation (2.5±0.06 %/day), S-F (2.5±0.11 %/day) and R-F (2.4±0.18 %/day) were significantly higher than that of CRestricted (2.2±0.05 %/day) or S-R (2.0±0.01 %/day). Fish in S-F group was able to achieve catching up with the CSatiation. There was no significant difference in feed conversion rates but R-F and S-F consumed ~34% more feed than CSatiation following the first re-feeding day. While the highest lipid content was observed in CSatiation (14.4 %), S-R (33.3 % dry matter) had the highest water content compare to the CSatiation and CRestricted (37.8 and 36.9 % dry matter, respectively). In conclusion, it may be concluded that sea bass has rapid response to cycling starvation/re-feeding and that a 25% restricted feeding ratio is insufficient to invoke a compensatory growth response in sea bass.

Link to article: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2109.2011.02970.x/abstract

Thermal tolerance of European sea bass

Screen Shot 2015-04-02 at 12.09.23 AMThis study was carried out to determine upper (CTMax) and lower (CTMin) thermal tolerance, acclimation response ratio (ARR) and thermal tolerance polygon of the European sea bass inhabiting the Iskenderun Bay, the most southeasterly part of the Mediterranean Sea, at three acclimation temperatures (15, 20, 25 °C). Acclimation temperature significantly affected the CTMin and CTMax values of the fish. At 0.3 °C/min cooling or heating rate, CTMin ranged from 4.10 to 6.77 °C and CTMax ranged from 33.23 to 35.95 °C in three acclimation temperatures from 15 to 25 °C. Thermal tolerance polygon for the juveniles at the tested acclimation temperatures was calculated to be 296.14 °C. In general, the current data show that our sea bass population possesses acclimation response ratio (ARR) values (0.25–0.27) similar to some tropical species. The cold tolerance values attained for this species ranged from 4.10 to 6.77 °C, suggesting that cold winter temperatures may not pose danger during the culture of European sea bass in deep ponds or high water exchange rate systems. Upper thermal tolerance is more of a problem in the southern part of the Mediterranean as maximum water temperature in ponds may sometimes exceed 33–34 °C, during which underground cool-water should be used to lower ambient water temperature in the mid-summer. For successful culture of sea bass in ponds, temperature should be maintained around 25 °C throughout the year and this can be managed under greenhousing systems using underground well-waters, commonly available in the region.

Effects of Salinity and Acclimation Temperature on CTMin of Whiteleg shrimp

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Critical thermal minima (CTmin) values were determined for the Pacific white shrimp Litopenaeus vannamei juveniles at combination of four different acclimation temperatures (15, 20, 25, and 30°C) and salinity levels (10, 20, 30, and 40‰). The lowest and highest CTmin of shrimps ranged between 7.2°C at 15°C/30‰ and 11.44°C at 30°C/20‰ at cooling rate of 1°C h-1. Acclimation temperature and salinity, as well as the interaction of both parameters, had significant effects on the CTmin values of L. vannamei (P<0.01). Yet, the results showed a much more profound effect of temperature on low thermal tolerance of juveniles. Only, 40‰ salinity had an influence on the CTmin values (P<0.01). As the acclimation-temperature was lowered from 30°C to 15°C, the thermal tolerance of the shrimp significantly increased up by 3.25–4.14°C. The acclimation response ratio (ARR) of the Pacific white shrimp exposed to different combinations of salinity and temperature ranged from 0.25 to 0.27. When this species is farmed in sub-tropical regions, its pond water temperature in the over-wintering facilities (regardless of the water salinity level) must never fall below 12°C throughout the cold-season to prevent mortalities.

Link to article, http://www.sciencedirect.com/science/article/pii/S0306456510000641

Thermal tolerance of Whiteleg Shrimp

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Critical thermal minima (CTMin) and maxima (CTMax) values were determined for the Pacific white shrimp Litopenaeus vannamei post-larvae and juveniles at four different acclimation temperatures (15, 20, 25, and 30 °C). The CTMin of shrimp at these acclimation temperatures were 7.82, 8.95, 9.80, and 10.96 °C for post-larvae and 7.50, 8.20, 10.20, and 10.80 °C for juveniles, respectively, at 1 °C/h cooling rate. The CTMax values were 35.65, 38.13, 39.91, and 42.00 °C for post-larvae and 35.94, 38.65, 40.30, and 42.20 °C for juveniles at the respective acclimation temperatures. Both acclimation temperature and size of the shrimp affected CTMin values of L. vannamei (P<0.01). Overall, juveniles displayed significantly lower CTMin values than the post-larvae (P<0.0001). However, the CTMax response by post-larvae and juveniles were not significantly different from each other and no interaction was determined between the acclimation temperature and development stage (P<0.01). The area of the thermal tolerance polygon over four acclimation temperatures (15, 20, 25, and 30 °C) for the post-larvae of L. vannamei was calculated to be 434.94 °C. The acclimation response ratio (ARR) values were high ranging from 0.35 to 0.44 for both post-larvae and juveniles. L. vannamei appears to be more sensitive to low temperatures than other penaeid species and its cold tolerance zone ranged from 7.5 to 11 °C. In successful aquaculture temperature must never fall below 12 °C to prevent mortalities. Upper thermal tolerance is less of a problem as in most subtropical regions maximum water temperature rarely exceeds 34 °C, but care should be given if shallow ponds with low water renewal rate are being used.

Link to article, http://www.sciencedirect.com/science/article/pii/S0306456510000653

Off-season Maturation and Spawning of Whiteleg Shrimp in Subtropical Conditions

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This study deals with investigations on how to control off-season maturation and spawning of Pacific white shrimp Litopenaeus vannamei by using various maturation techniques. For the experiment, the broodstock were separated into five groups (Group 1: Control, Group 2: Serotonin-injected, Group 3: Ablated, Group 4: Temperature-fluctuated, and Group 5: Another ablated groups). Each of the first four groups were stocked into a 2-m diameter round tank at density of 9.44 shrimps per m2 (2:1, female/male), while Group 5 were stocked into a 3-m diameter tank at density of 5.67 shrimps per m2 (1:1, female/male). The experiment continued for 2 months until maturation in a recirculation system. Each female was tagged and any ripe female carrying a spermatophore was removed to spawn individually in a spawning tank. The first spawnings occurred on 25-28th days of the experiment in all the groups. The highest female spawning rate (55-90%) and fecundity (79,778-125,015 eggs) were obtained in the eyestalk-ablated groups (P<0.05). Serotonin (Group 2) induced ovarium development in 35% of the females, generating 60,277 eggs per female. Cyclic temperature fluctuation (Group 4) stimulated ovarium maturation in 39% of the females with a mean fecundity of 28,500 eggs per female (P<0.05). Mean egg fertility rates ranged from 63.08% to 96%, and hatching rates from 8.53% to 31%. Spawning, fecundity and hatching rates were found to be different between the two eyestalk-ablated groups (Group 3 and 5), and the reasons were thought to be due to tank size and/or shrimp stocking density. Our broodstock displayed poor reproductive performance with abnormal egg morphology and low egg hatching rates. The stress caused by off-season reproduction and low genetic variation due to past selective breeding programs might have seriously hampered the reproductive performance of our broodstock. The results of this study has demonstrated that, under Mediterranean climatic conditions, the broodstock of this non-indigenous shrimp species can be readily matured and spawned out of season in recirculating systems.

Link to full text: http://www.trjfas.org/pdf/issue_11_01/0103.pdf