Nutrigenomic and Nutritional Analyses Reveal the Effects of Pelleted Feeds on Asian Seabass (Lates calcarifer)

Abstract

As nutrition-related expenses constitute the majority of the costs for aquaculture farms, it is essential for them to use feeds that provide an ideal combination of nutrients for the species of choice. In this study, the relative effect of consuming three different pelleted feeds (B, C and D) in comparison to frozen baitfish (A; control) were compared on juvenile Asian seabass (77.3 ± 22.4g) that were selected for increased growth rate over two generations. Our objectives were: 1) to evaluate the effects of different pelleted feeds based on overall physiological changes and nutritional quality of fillets; 2) improve our understanding of the underlying mechanisms with transcriptomic analysis; 3) if possible, identify the feed type that supports the growth of these fishes without substantially reducing the nutritional quality of fillet. The growth performance, fatty acid composition of fillet, hepatic histology and transcriptome of the fishes (Groups A-D) were analyzed. The majority of fatty acids of the fillets, except γ-linolenic acid (GLA, C18:3n6), correlated significantly with the respective diets. Asian seabass fed Feed C showed highest specific growth rate (SGR) and feed conversion efficiency (FCE) with closest histology and transcriptomic profile to control, but their fillet contained the highest n6/n3 ratio. When the liver-based transcriptomes were analyzed, a complex set of differentially expressed genes were detected between groups fed pelleted feeds and controls as well as among the pellet-fed groups themselves. Significant enrichment of genes with growth-related function tallied with the morphological data measured. When compared with control (Group A), ‘Biosynthesis of unsaturated fatty acids’ and ‘Steroid biosynthesis’ pathways were significantly enriched in pellet-fed groups. Reduced goblet cell numbers were observed in the gut of pellet-fed fish compared to controls and fads6 was found to be a suitable candidate gene to separate wild-caught Asian seabass, from pellet-fed ones. These results provide insights for researchers on the various effects of feeds on the biochemistry and global gene expression of the fish and potentially for seabass farms to make more informed feed choices.

Identification of Fatty Acid Desaturase 6 in Golden Pompano Trachinotus Ovatus (Linnaeus 1758) and Its Regulation by the PPARαb Transcription Factor

“…In this study, the functional characteristics of T. ovatus Fads6 , via heterologous expression in S. cerevisiae, indicated that the T. ovatus putative desaturase was Fads6 , with Δ4 desaturation activity. This was functionally similar to the Fads6 from Arabidopsis thaliana , Medicago truncatula , and Homo sapiens [12,13,14]. T. ovatus Fads6 exhibited low activity towards 22:4n-6 and 22:5n-3 substrates, such as 22:5n-6 (1.04%) and 22:6n-3 (39.29%).…”

“…Previous studies using yeast heterologous expression systems have indicated that Fads2 exhibits ∆6, ∆5, ∆4, and ∆8 activity in the biosynthetic pathway of LC-PUFAs [1,4,7,8,9,10,11]; however, little information on Fads6 has been reported. Ngoh et al (2015) [12] revealed that fads6 expression was detected to be underlying, and suitable as a bioindicator to identify wild and farmed Lates calcarifer [1,2]. Some studies stated that Fads6 is involved with lipid and fatty acid metabolism in Homo sapiens [13,14].…”

Dietary tuna hydrolysate modulates growth performance, immune response, intestinal morphology and resistance to Streptococcus iniae in juvenile barramundi, Lates calcarifer

“…Lates calcarifer , a euryhaline carnivorous fish species commonly known as barramundi or Asian sea bass, is widely cultured throughout the Indo-Pacific region and Australia 1 , 2 . Currently, the commercial farming of this species is well established in ponds, net cages and recirculating aquaculture systems (RAS) in both fresh and saline water.…”

Morpho-histological characterisation of the alimentary canal of an important food fish, Asian seabass (Lates calcarifer)

“…The Asian seabass ( Lates calcarifer ; Centropomidae ), also known as barramundi or giant perch, is an important food fish in many parts of the world ( Nelson, 2006 ; Vij et al, 2016 ; Vij et al, 2014 ). As such, there has been an increasing interest in its growth mechanism and nutritional needs in recent years, especially with a view to improve the production of good fillet of marketable quantity and quality ( Alhazzaa et al, 2011 ; Glencross et al, 2008 ; Katersky & Carter, 2009 ; Matthews et al, 1997 ; Ngoh et al, 2015 ; Srichanun et al, 2013 ; Tu et al, 2013 ; Xia et al, 2013 ).…”

“…Over the past two decades, an increasing number of research projects and publications have been focusing on the Asian seabass ( Kuznetsova et al, 2014 ; Ngoh et al, 2015 ). Selection projects utilized the tools of molecular genetics to improve seabass lines ( Wang et al, 2011 ; Wang et al, 2006 ), transcriptomic studies have analyzed the genetic regulation of its sex change ( Ravi et al, 2014 ) or responses to a vaccine and bacterial infection ( Jiang et al, 2014 ) and others have investigated the evolution of the species ( Vij et al, 2016 ; Vij et al, 2014 ).…”