Physical properties of commercial infant milk formula products

[EN] The physical properties of 12 commercially available infant milk formula (IMF) and follow-on (FO) powders were assessed. Polarised light micrographs of powders revealed that two types of powders existed: Type I - homogenous mixtures of milk powder particles and Type II – heterogeneous mixtures of milk powder particles and tomahawk-shaped a-lactose monohydrate crystals. Conventionally employed correlations between particle size, flowability and compressibility were found to be highly dependent on the presence of crystalline lactose in powders. Overall, results showed the importance of micro-structural evaluation during analysis of physical properties of dairy powders and, in particular, IMF/FO powders.Murphy, E.; Regost, N.; Roos, Y.; Fenelon, M. (2018). Physical properties of commercial infant milk formula products. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 765-772. https://doi.org/10.4995/IDS2018.2018.7413OCS76577

Ovary and egg fatty acid composition of greater amberjack broodstock (Seriola dumerili) fed different dietary fatty acids profiles

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Cloning and functional characterisation of polyunsaturated fatty acid elongases of marine and freshwater teleost fish

Enzymes that lengthen the carbon chain of polyunsaturated fatty acids are key to the biosynthesis of the highly unsaturated fatty acids, arachidonic, eicosapentaenoic and docosahexaenoic acids from linoleic and α-linolenic acids. A Mortierella alpina cDNA polyunsaturated fatty acid elongase sequence identified mammalian, amphibian, zebrafish and insect expressed sequence tags (ESTs) in GenBank. Consensus primers were designed in conserved motifs and used to isolate full length cDNA from livers of several fish species by Rapid Amplification of cDNA Ends (RACE). The amplified cDNAs encoded putative open reading frames (ORFs) of 288-294 amino acids that were highly conserved among the fish species. Heterologous expression in yeast, Saccharomyces cerevisiae, demonstrated that all of the ORFs encoded elongases with the ability to lengthen polyunsaturated fatty acid substrates with chain lengths from C18 to C22 and also monounsaturated fatty acids, but not saturated fatty acids. There were differences in the functional competence of the elongases from different fish species. Most of the fish elongases showed a pattern of activity towards different fatty acid substrates in the rank order C18 > C20 >C22, although the tilapia and turbot elongases had similar activity towards 18:4n-3 and 20:5n-3. The fish elongases generally showed greater activity or similar activities with n-3 than with n-6 homologues, with the exception of the cod enzyme which was more active towards n-6 fatty acids

Highly Unsaturated Fatty Acid Synthesis in Atlantic Salmon: Characterization of ELOVL5- and ELOVL2-like Elongases

Fish species vary in their capacity to biosynthesize the n-3 long-chain polyunsaturated fatty acids (LC-PUFA) eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids that are crucial to the health of higher vertebrates. The synthesis of LC-PUFA involves enzyme-mediated fatty acyl desaturation and elongation. Previously, a cDNA for an elongase, now termed elovl5a, had been cloned from Atlantic salmon. Here we report on the cloning of two new elongase cDNAs: a second elovl5b elongase, corresponding to a 294 aa protein, and an elovl2-like elongase, coding for a 287 aa protein, characterized for the first time in a non-mammalian vertebrate. Heterologous expression in yeast showed that the salmon Elovl5b elongated C18 and C20 PUFA, with low activity towards C22, while Elovl2 elongated C20 and C22 PUFA with lower activity towards C18 PUFA. All three transcripts showed predominant expression in the intestine and liver, followed by the brain. Elongase expression showed differential nutritional regulation. Levels of elovl5b and particularly of elovl2, but not of elovl5a, transcripts were significantly increased in liver of salmon fed vegetable oils (VO) compared to fish fed fish oil (FO). Intestinal expression showed a similar pattern. Phylogenetic comparisons indicate that, in contrast to salmon and zebrafish, Acanthopterygian fish species lack elovl2 which is consistent with their neglible ability to biosynthesise LC-PUFA and to adapt to VO dietary inclusion, compared to predominantly freshwater salmonids. Thus the presence of elovl2 in salmon explains the ability of this species to biosynthesise LC-HUFA and may provide a biotechnological tool to produce enhanced levels of LC-PUFA, particularly DHA, in transgenic organisms

Growth, sensory and chemical characterization of Mediterranean yellowtail (Seriola dumerili) fed diets with partial replacement of fish meal by other protein sources

[EN] An 84-day trial was performed to assess the use of alternative protein sources in Seriola dumerili. Three diets were used, FM100 diet, as a control diet without fishmeal substitution, and FM66 and FM33 diets with a fishmeal replacement of 330 g/kg and 660 g/kg, respectively. At the end of experiment, fish fed the FM66 diet showed the no differences in growth, nutritional parameters and fatty acid composition. Heavy metals present some differences but are always lower than risk levels. In sensory analysis, differences between diets appeared in pH and color, and also in some texture parameters between FM33 and the other two diets. No differences appeared between diets related to flavor. In summary, long periods of feeding with high fish meal substitution diets, affects Seriola dumerili growth; despite this the quality of the fillet was not affected even with a 66 % of substitution.This project was financed by "Generalitat Valenciana. Ayudas para grupos de investigacion consolidables."Monge-Ortiz, R.; Martínez-Llorens, S.; Lemos-Neto, M.; Falco, S.; Pagán Moreno, MJ.; Godoy-Olmos, S.; Jover Cerda, M.... (2020). Growth, sensory and chemical characterization of Mediterranean yellowtail (Seriola dumerili) fed diets with partial replacement of fish meal by other protein sources. Aquaculture Reports. 18:1-10. https://doi.org/10.1016/j.aqrep.2020.100466S11018Abbas, K. A., Mohamed, A., Jamilah, B., & Ebrahimian, M. (2008). A Review on Correlations between Fish Freshness and pH during Cold Storage. American Journal of Biochemistry and Biotechnology, 4(4), 416-421. doi:10.3844/ajbbsp.2008.416.421Álvarez, A., García García, B., Garrido, M. D., & Hernández, M. D. (2008). The influence of starvation time prior to slaughter on the quality of commercial-sized gilthead seabream (Sparus aurata) during ice storage. Aquaculture, 284(1-4), 106-114. doi:10.1016/j.aquaculture.2008.07.025AMIARD, J., AMIARDTRIQUET, C., BARKA, S., PELLERIN, J., & RAINBOW, P. (2006). Metallothioneins in aquatic invertebrates: Their role in metal detoxification and their use as biomarkers. Aquatic Toxicology, 76(2), 160-202. doi:10.1016/j.aquatox.2005.08.015Baeverfjord, G., Refstie, S., Krogedal, P., & Åsgård, T. (2006). Low feed pellet water stability and fluctuating water salinity cause separation and accumulation of dietary oil in the stomach of rainbow trout (Oncorhynchus mykiss). Aquaculture, 261(4), 1335-1345. doi:10.1016/j.aquaculture.2006.08.033Baeza-Ariño, R., Martínez-Llorens, S., Nogales-Mérida, S., Jover-Cerda, M., & Tomás-Vidal, A. (2014). Study of liver and gut alterations in sea bream,Sparus aurataL., fed a mixture of vegetable protein concentrates. Aquaculture Research, 47(2), 460-471. doi:10.1111/are.12507Bell, J. G., McEvoy, J., Tocher, D. R., McGhee, F., Campbell, P. J., & Sargent, J. R. (2001). Replacement of Fish Oil with Rapeseed Oil in Diets of Atlantic Salmon (Salmo salar) Affects Tissue Lipid Compositions and Hepatocyte Fatty Acid Metabolism. The Journal of Nutrition, 131(5), 1535-1543. doi:10.1093/jn/131.5.1535Benedito-Palos, L., Navarro, J. C., Sitjà-Bobadilla, A., Gordon Bell, J., Kaushik, S., & Pérez-Sánchez, J. (2008). High levels of vegetable oils in plant protein-rich diets fed to gilthead sea bream (Sparus aurataL.): growth performance, muscle fatty acid profiles and histological alterations of target tissues. British Journal of Nutrition, 100(5), 992-1003. doi:10.1017/s0007114508966071Bjerkeng, B., Refstie, S., Fjalestad, K. T., Storebakken, T., Rødbotten, M., & Roem, A. J. (1997). Quality parameters of the flesh of Atlantic salmon (Salmo salar) as affected by dietary fat content and full-fat soybean meal as a partial substitute for fish meal in the diet. Aquaculture, 157(3-4), 297-309. doi:10.1016/s0044-8486(97)00162-2De Francesco, M., Parisi, G., Médale, F., Lupi, P., Kaushik, S. J., & Poli, B. M. (2004). Effect of long-term feeding with a plant protein mixture based diet on growth and body/fillet quality traits of large rainbow trout (Oncorhynchus mykiss). Aquaculture, 236(1-4), 413-429. doi:10.1016/j.aquaculture.2004.01.006DE FRANCESCO, M., PARISI, G., PÉREZ-SÁNCHEZ, J., GÓMEZ-RéQUENI, P., MÉDALE, F., KAUSHIK, S. J., … POLI, B. M. (2007). Effect of high-level fish meal replacement by plant proteins in gilthead sea bream (Sparus aurata) on growth and body/fillet quality traits. Aquaculture Nutrition, 13(5), 361-372. doi:10.1111/j.1365-2095.2007.00485.xEstruch, G., Collado, M. C., Peñaranda, D. S., Tomás Vidal, A., Jover Cerdá, M., Pérez Martínez, G., & Martinez-Llorens, S. (2015). Impact of Fishmeal Replacement in Diets for Gilthead Sea Bream (Sparus aurata) on the Gastrointestinal Microbiota Determined by Pyrosequencing the 16S rRNA Gene. PLOS ONE, 10(8), e0136389. doi:10.1371/journal.pone.0136389Estruch, G., Collado, M. C., Monge-Ortiz, R., Tomás-Vidal, A., Jover-Cerdá, M., Peñaranda, D. S., … Martínez-Llorens, S. (2018). Long-term feeding with high plant protein based diets in gilthead seabream (Sparus aurata, L.) leads to changes in the inflammatory and immune related gene expression at intestinal level. BMC Veterinary Research, 14(1). doi:10.1186/s12917-018-1626-6Estruch, G., Tomás-Vidal, A., El Nokrashy, A. M., Monge-Ortiz, R., Godoy-Olmos, S., Jover Cerdá, M., & Martínez-Llorens, S. (2018). Inclusion of alternative marine by-products in aquafeeds with different levels of plant-based sources for on-growing gilthead sea bream (Sparus aurata, L.): effects on digestibility, amino acid retention, ammonia excretion and enzyme activity. Archives of Animal Nutrition, 72(4), 321-339. doi:10.1080/1745039x.2018.1472408Estruch, G., Martínez-Llorens, S., Tomás-Vidal, A., Monge-Ortiz, R., Jover-Cerdá, M., Brown, P. B., & Peñaranda, D. S. (2020). Impact of high dietary plant protein with or without marine ingredients in gut mucosa proteome of gilthead seabream (Sparus aurata, L.). Journal of Proteomics, 216, 103672. doi:10.1016/j.jprot.2020.103672Fountoulaki, E., Vasilaki, A., Hurtado, R., Grigorakis, K., Karacostas, I., Nengas, I., … Alexis, M. N. (2009). Fish oil substitution by vegetable oils in commercial diets for gilthead sea bream (Sparus aurata L.); effects on growth performance, flesh quality and fillet fatty acid profile. Aquaculture, 289(3-4), 317-326. doi:10.1016/j.aquaculture.2009.01.023Francis, G., Makkar, H. P. ., & Becker, K. (2001). Antinutritional factors present in plant-derived alternate fish feed ingredients and their effects in fish. Aquaculture, 199(3-4), 197-227. doi:10.1016/s0044-8486(01)00526-9Korkmaz Görür, F., Keser, R., Akçay, N., & Dizman, S. (2012). Radioactivity and heavy metal concentrations of some commercial fish species consumed in the Black Sea Region of Turkey. Chemosphere, 87(4), 356-361. doi:10.1016/j.chemosphere.2011.12.022Hu, L., Yun, B., Xue, M., Wang, J., Wu, X., Zheng, Y., & Han, F. (2013). Effects of fish meal quality and fish meal substitution by animal protein blend on growth performance, flesh quality and liver histology of Japanese seabass (Lateolabrax japonicus). Aquaculture, 372-375, 52-61. doi:10.1016/j.aquaculture.2012.10.025Izquierdo, M. S., Obach, A., Arantzamendi, L., Montero, D., Robaina, L., & Rosenlund, G. (2003). Dietary lipid sources for seabream and seabass: growth performance, tissue composition and flesh quality. Aquaculture Nutrition, 9(6), 397-407. doi:10.1046/j.1365-2095.2003.00270.xIzquierdo, M. S., Montero, D., Robaina, L., Caballero, M. J., Rosenlund, G., & Ginés, R. (2005). Alterations in fillet fatty acid profile and flesh quality in gilthead seabream (Sparus aurata) fed vegetable oils for a long term period. Recovery of fatty acid profiles by fish oil feeding. Aquaculture, 250(1-2), 431-444. doi:10.1016/j.aquaculture.2004.12.001Jover, M., Garcı́a-Gómez, A., Tomás, A., De la Gándara, F., & Pérez, L. (1999). Growth of mediterranean yellowtail (Seriola dumerilii) fed extruded diets containing different levels of protein and lipid. Aquaculture, 179(1-4), 25-33. doi:10.1016/s0044-8486(99)00149-0Martínez-Llorens, S., Baeza-Ariño, R., Nogales-Mérida, S., Jover-Cerdá, M., & Tomás-Vidal, A. (2012). Carob seed germ meal as a partial substitute in gilthead sea bream (Sparus aurata) diets: Amino acid retention, digestibility, gut and liver histology. Aquaculture, 338-341, 124-133. doi:10.1016/j.aquaculture.2012.01.029MARTINS, D. A., VALENTE, L. M. P., & LALL, S. P. (2011). Partial replacement of fish oil by flaxseed oil in Atlantic halibut (Hippoglossus hippoglossus L.) diets: effects on growth, nutritional and sensory quality. Aquaculture Nutrition, 17(6), 671-684. doi:10.1111/j.1365-2095.2011.00869.xMatallanas, J., Casadevall, M., Carrasson, M., Bolx, J., & Fernandez, V. (1995). The Food of Seriola Dumerili (Pisces: Carangidae) in the Catalan Sea (Western Mediterranean). Journal of the Marine Biological Association of the United Kingdom, 75(1), 257-260. doi:10.1017/s0025315400015356Monge-Ortiz, R., Tomás-Vidal, A., Gallardo-Álvarez, F. J., Estruch, G., Godoy-Olmos, S., Jover-Cerdá, M., & Martínez-Llorens, S. (2018). Partial and total replacement of fishmeal by a blend of animal and plant proteins in diets for Seriola dumerili : Effects on performance and nutrient efficiency. Aquaculture Nutrition, 24(4), 1163-1174. doi:10.1111/anu.12655Monge-Ortiz, R., Tomás-Vidal, A., Rodriguez-Barreto, D., Martínez-Llorens, S., Pérez, J. A., Jover-Cerdá, M., & Lorenzo, A. (2017). Replacement of fish oil with vegetable oil blends in feeds for greater amberjack (Seriola dumerili) juveniles: Effect on growth performance, feed efficiency, tissue fatty acid composition and flesh nutritional value. Aquaculture Nutrition, 24(1), 605-615. doi:10.1111/anu.12595Mourente, G., & Bell, J. G. (2006). Partial replacement of dietary fish oil with blends of vegetable oils (rapeseed, linseed and palm oils) in diets for European sea bass (Dicentrarchus labrax L.) over a long term growth study: Effects on muscle and liver fatty acid composition and effectiveness of a fish oil finishing diet. Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 145(3-4), 389-399. doi:10.1016/j.cbpb.2006.08.012Nanton, D. A., Vegusdal, A., Rørå, A. M. B., Ruyter, B., Baeverfjord, G., & Torstensen, B. E. (2007). Muscle lipid storage pattern, composition, and adipocyte distribution in different parts of Atlantic salmon (Salmo salar) fed fish oil and vegetable oil. Aquaculture, 265(1-4), 230-243. doi:10.1016/j.aquaculture.2006.03.053O’Fallon, J. V., Busboom, J. R., Nelson, M. L., & Gaskins, C. T. (2007). A direct method for fatty acid methyl ester synthesis: Application to wet meat tissues, oils, and feedstuffs. Journal of Animal Science, 85(6), 1511-1521. doi:10.2527/jas.2006-491Olsen, R. L., & Toppe, J. (2017). Fish silage hydrolysates: Not only a feed nutrient, but also a useful feed additive. Trends in Food Science & Technology, 66, 93-97. doi:10.1016/j.tifs.2017.06.003De Paiva, E. L., Alves, J. C., Milani, R. F., Boer, B. S., Quintaes, K. D., & Morgano, M. A. (2016). Sushi commercialized in Brazil: Organic Hg levels and exposure intake evaluation. Food Control, 69, 115-123. doi:10.1016/j.foodcont.2016.04.029Panserat, S., Hortopan, G. A., Plagnes-Juan, E., Kolditz, C., Lansard, M., Skiba-Cassy, S., … Corraze, G. (2009). Differential gene expression after total replacement of dietary fish meal and fish oil by plant products in rainbow trout (Oncorhynchus mykiss) liver. Aquaculture, 294(1-2), 123-131. doi:10.1016/j.aquaculture.2009.05.013Piazzon, M. C., Calduch-Giner, J. A., Fouz, B., Estensoro, I., Simó-Mirabet, P., Puyalto, M., … Pérez-Sánchez, J. (2017). Under control: how a dietary additive can restore the gut microbiome and proteomic profile, and improve disease resilience in a marine teleostean fish fed vegetable diets. Microbiome, 5(1). doi:10.1186/s40168-017-0390-3Regost, C., Arzel, J., Robin, J., Rosenlund, G., & Kaushik, S. . (2003). Total replacement of fish oil by soybean or linseed oil with a return to fish oil in turbot (Psetta maxima). Aquaculture, 217(1-4), 465-482. doi:10.1016/s0044-8486(02)00259-4Robaina, L., Izquierdo, M. ., Moyano, F. ., Socorro, J., Vergara, J. ., & Montero, D. (1998). Increase of the dietary n−3/n−6 fatty acid ratio and addition of phosphorus improves liver histological alterations induced by feeding diets containing soybean meal to gilthead seabream, Sparus aurata. Aquaculture, 161(1-4), 281-293. doi:10.1016/s0044-8486(97)00276-7Serradell, A., Torrecillas, S., Makol, A., Valdenegro, V., Fernández-Montero, A., Acosta, F., … Montero, D. (2020). Prebiotics and phytogenics functional additives in low fish meal and fish oil based diets for European sea bass (Dicentrarchus labrax): Effects on stress and immune responses. Fish & Shellfish Immunology, 100, 219-229. doi:10.1016/j.fsi.2020.03.016Shimeno, S., Masumoto, T., Hujita, T., Mima, T., & Ueno, S. (1993). Protein Source for Fish Feed-V. Alternative Protein Sources for Fish Meal in Diets of Young Yellowtail. NIPPON SUISAN GAKKAISHI, 59(1), 137-143. doi:10.2331/suisan.59.137Sitjà-Bobadilla, A., Peña-Llopis, S., Gómez-Requeni, P., Médale, F., Kaushik, S., & Pérez-Sánchez, J. (2005). Effect of fish meal replacement by plant protein sources on non-specific defence mechanisms and oxidative stress in gilthead sea bream (Sparus aurata). Aquaculture, 249(1-4), 387-400. doi:10.1016/j.aquaculture.2005.03.031SLOTH, J. J., JULSHAMN, K., & LUNDEBYE, A.-K. (2005). Total arsenic and inorganic arsenic content in Norwegian fish feed products. Aquaculture Nutrition, 11(1), 61-66. doi:10.1111/j.1365-2095.2004.00334.xStergiou, K. I., & Karpouzi, V. S. (2001). Reviews in Fish Biology and Fisheries, 11(3), 217-254. doi:10.1023/a:1020556722822Thakur, D. P., Morioka, K., Itoh, N., Wada, M., & Itoh, Y. (2009). Muscle biochemical constituents of cultured amberjack Seriola dumerili and their influence on raw meat texture. Fisheries Science, 75(6), 1489-1498. doi:10.1007/s12562-009-0173-2TOMAS, A., DE LA GANDARA, F., GARCIA-GOMEZ, A., PEREZ, L., & JOVER, M. (2005). Utilization of soybean meal as an alternative protein source in the Mediterranean yellowtail, Seriola dumerili. Aquaculture Nutrition, 11(5), 333-340. doi:10.1111/j.1365-2095.2005.00365.xTomás‐Vidal, A., Monge‐Ortiz, R., Jover‐Cerdá, M., & Martínez‐Llorens, S. (2019). Apparent digestibility and protein quality evaluation of selected feed ingredients in Seriola dumerili. Journal of the World Aquaculture Society, 50(4), 842-855. doi:10.1111/jwas.12597Torstensen, B. E., Bell, J. G., Rosenlund, G., Henderson, R. J., Graff, I. E., Tocher, D. R., … Sargent, J. R. (2005). Tailoring of Atlantic Salmon (Salmo salar L.) Flesh Lipid Composition and Sensory Quality by Replacing Fish Oil with a Vegetable Oil Blend. Journal of Agricultural and Food Chemistry, 53(26), 10166-10178. doi:10.1021/jf051308iTurchini, G. M., Moretti, V. M., Mentasti, T., Orban, E., & Valfrè, F. (2007). Effects of dietary lipid source on fillet chemical composition, flavour volatile compounds and sensory characteristics in the freshwater fish tench (Tinca tinca L.). Food Chemistry, 102(4), 1144-1155. doi:10.1016/j.foodchem.2006.07.003Valente, L. M. P., Linares, F., Villanueva, J. L. R., Silva, J. M. G., Espe, M., Escórcio, C., … Peleteiro, J. B. (2011). Dietary protein source or energy levels have no major impact on growth performance, nutrient utilisation or flesh fatty acids composition of market-sized Senegalese sole. Aquaculture, 318(1-2), 128-137. doi:10.1016/j.aquaculture.2011.05.026Watanabe, K., Ura, K., Yada, T., Kiron, V., Satoh, S., & Watanabe, T. (2000). Energy and protein requirements of yellowtail for maximum growth and maintenance of body weight. Fisheries Science, 66(6), 1053-1061. doi:10.1046/j.1444-2906.2000.00168.

Transcriptomic analyses of intestinal gene expression of juvenile Atlantic cod (Gadus morhua) fed diets with Camelina oil as replacement for fish oil

For aquaculture of marine species to continue to expand, dietary fish oil (FO) must be replaced with more sustainable vegetable oil (VO) alternatives. Most VO are rich in n-6 polyunsaturated fatty acids (PUFA) and few are rich in n-3 PUFA but Camelina oil (CO) is unique in that, besides high 18:3n-3 and n-3/n-6 PUFA ratio, it also contains substantial long-chain monoenes, commonly found in FO. Cod (initial weight ~1.4 g) were fed for 12 weeks diets in which FO was replaced with CO. Growth performance, feed efficiency and biometric indices were not affected but lipid levels in liver and intestine tended to increase and those of flesh, decrease, with increasing dietary CO although only significantly for intestine. Reflecting diet, tissue n-3 long-chain PUFA levels decreased whereas 18:3n-3 and 18:2n-6 increased with inclusion of dietary CO. Dietary replacement of FO by CO did not induce major metabolic changes in intestine, but affected genes with potential to alter cellular proliferation and death as well as change structural properties of intestinal muscle. Although the biological effects of these changes are unclear, given the important role of intestine in nutrient absorption and health, further attention should be given to this organ in future

Highly unsaturated fatty acid synthesis in marine fish: Cloning, functional characterization, and nutritional regulation of fatty acyl delta6 desaturase of Atlantic cod (Gadus morhua L.)

Fish contain high levels of the n-3 highly unsaturated fatty acids (HUFA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids that are crucial to the health of higher vertebrates. Biosynthesis of HUFA requires enzyme-mediated desaturation of fatty acids. Here we report cloning and functional characterisation of a ∆6 fatty acyl desaturase of Atlantic cod (Gadus morhua), and describe its tissue expression and nutritional regulation. PCR primers were designed based on the sequences of conserved motifs in available fish desaturases and used to isolate a cDNA fragment from liver of cod. The full-length cDNA was obtained by Rapid Amplification of cDNA Ends (RACE). The cDNA for the putative fatty acyl desaturase was shown to comprise 1980bp which included a 5’-UTR of 261bp and a 3’-UTR of 375bp. Sequencing revealed that the cDNA included an ORF of 1344 bp that specified a protein of 447 amino acids. The protein sequence included three histidine boxes, two transmembrane regions, and an N-terminal cytochrome b5 domain containing the haem-binding motif HPGG, all of which are characteristic of microsomal fatty acid desaturases. The cDNA displayed Δ6 desaturase activity in a heterologous yeast expression system. Quantitative real time PCR assay of gene expression in cod showed that the ∆6 desaturase gene, was highly expressed in brain, relatively highly expressed in liver, kidney, intestine, red muscle and gill, and expressed at much lower levels in white muscle, spleen and heart. In contrast, the abundance of a cod fatty acyl elongase transcript was high in brain and gill, with intermediate levels in kidney, spleen, intestine and heart, and relatively low expression in liver. The expression of the Δ6 desaturase gene and the PUFA elongase gene may be under a degree of nutritional regulation, with levels being marginally increased in livers and intestine of fish fed a vegetable oil blend by comparison with levels in fish fed fish oil. However, this was not reflected in increased Δ6 desaturase activity in hepatocytes or enterocytes, which showed very little highly unsaturated fatty acid biosynthesis activity irrespective of diet. The study described has demonstrated that Atlantic cod express a fatty acid desaturase gene with functional Δ6 activity in a yeast expression system. This is consistent with an established hypothesis that the poor ability of marine fish to synthesise HUFA is not due to lack of a Δ6 desaturase, but rather to deficiencies in other parts of the biosynthetic pathway. However, further studies are required to determine why the Δ6 desaturase appears to be barely functional in cod under the conditions tested

Effects of the total replacement of fish-based diet with plant-based diet on the hepatic transcriptome of two European sea bass (Dicentrarchus labrax) half-sibfamilies showing different growth rates with the plant-based diet

Background: Efforts towards utilisation of diets without fish meal (FM) or fish oil (FO) in finfish aquaculture have been being made for more than two decades. Metabolic responses to substitution of fishery products have been shown to impact growth performance and immune system of fish as well as their subsequent nutritional value, particularly in marine fish species, which exhibit low capacity for biosynthesis of long-chain poly-unsaturated fatty acids (LC-PUFA). The main objective of the present study was to analyse the effects of a plant-based diet on the hepatic transcriptome of European sea bass (Dicentrarchus labrax). Results: We report the first results obtained using a transcriptomic approach on the liver of two half-sibfamilies of the European sea bass that exhibit similar growth rates when fed a fish-based diet (FD), but significantly different growth rates when fed an all-plant diet (VD). Overall gene expression was analysed using oligo DNA microarrays (GPL9663). Statistical analysis identified 582 unique annotated genes differentially expressed between groups of fish fed the two diets, 199 genes regulated by genetic factors, and 72 genes that exhibited diet-family interactions. The expression of several genes involved in the LC-PUFA and cholesterol biosynthetic pathways was found to be up-regulated in fish fed VD, suggesting a stimulation of the lipogenic pathways. No significant diet-family interaction for the regulation of LC-PUFA biosynthesis pathways could be detected by microarray analysis. This result was in agreement with LC-PUFA profiles, which were found to be similar in the flesh of the two half-sibfamilies. In addition, the combination of our transcriptomic data with an analysis of plasmatic immune parameters revealed a stimulation of complement activity associated with an immunodeficiency in the fish fed VD, and different inflammatory status between the two half-sibfamilies. Biological processes related to protein catabolism, amino acid transaminations, RNA splicing and blood coagulation were also found to be regulated by diet, while the expression of genes involved in protein and ATP synthesis differed between the half-sibfamilies. Conclusions: Overall, the combined gene expression, compositional and biochemical studies demonstrated a large panel of metabolic and physiological effects induced by total substitution of both FM and FO in the diets of European sea bass and revealed physiological characteristics associated with the two half-sibfamilies