Gastrointestinal modelling and optimization of protein and phosphorus bioaccessibility by phytase in fish diets

Programa de doctorado: Acuicultura

Marine and freshwater crab meals in diets for the red porgy (Pagrus pagrus): growth, colour, and fish composition

[EN] Red porgy, Pagrus pagrus, is one of the marine fish species for the aquaculture diversification in the Mediterranean and Mid Atlantic coasts. Relevance of its nutrition has been demonstrated not only from growth and body composition, but also because it?s important role in fish skin colour and carotenoids deposition (Kalinowski et al., 2005; Pavlidis et al., 2006). Present study evaluate the influence of two different crab meals by products, marine and freshwater origin, as protein and pigment sources in experimental diets for red porgy and its effects on fish growth and feed utilization parameters, fish skin colour and fish composition. Both crab meals used in present study are suitability as partial replacers of fish meal in diets for the red porgy. Dietary inclusion levels of 10% and 20% of the dietary protein from these meals have no detrimental effects on growth and feed utilization parameters respect to a fish meal based diet, with high improvements in fish skin redness and skin colour saturation by increased inclusion levels. Digestibility and retention efficiency parameters are being analyzing at the moment.

PepT1 mRNA expression levels in sea bream (Sparus aurata) fed different plant protein sources

[EN] The expression and regulation of intestinal oligopeptide transporter (PepT)-1 when vegetable sources are used as a substitute for fish meal in the diet of marine fish has not yet been explored. In the present study, as part of our ongoing work on elucidating PepT1 gene expression in relation to different dietary treatments, we have now isolated and deposited in Genbank database (accession no. GU733710) a cDNA sequence representing the PepT1 in the sea bream (Sparus aurata). The ?de novo? prediction of the three-dimensional structure of PepT1 protein is presented. We also analyzed diet-induced changes in the expression of PepT1 mRNA via real-time RT-PCR using the standard curve method. Sea bream were fed for 140 days with one of the following four diet formulations (43% protein/21% lipid): a control fast growth-promoting diet (C), and three diets with the same formulation but in which 15% of the fish meal was substituted by protein concentrates either from lupine (LPC), chick pea (CPC), or green pea (PPC). Fish fed PPC had significantly (p < 0.05) lower levels of PepT1 transcripts in the proximal intestine than the controls, whereas PepT1 transcript levels in fish fed LPC or CPC were not significantly different from the controls. Although growth was similar between fish fed with different diets during the first 72 days of feeding, growth of the fish fed with PPC was reduced during the second part of the trial and was significantly (p < 0.05) lower than fish fed LPC and CPC diets by the end of the experiment. Correlation between these results and fish growth performances highlights that the intestinal PepT1 mRNA level may serve as a useful marker of the dietary protein quality and absorption efficiency.