Digestive enzymes of meagre (Argyrosomus regius) and white seabream (Diplodus sargus). Effects of dietary brewer's spent yeast supplementation Carolina Castro a,b, ⁎, Amalia Pérez-Jiménez a,c , Filipe Coutinho a,b , Pedro Pousão-Ferreira d , Tiago M. Brandão e , Aires Oliva-Teles a,b , Helena Peres a a CIMAR/CIIMAR—Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal b Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, Edifício FC4, 4169-007 Porto, Portugal c Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva s/n, 18071 Granada, Spain d IPMA, Aquaculture Research Centre/Estação Piloto de Piscicultura de Olhão, Olhão, Portugal e Unicer Bebidas, SA, Via Norte, Leça do Balio, Portugal abstract article info Article history: Received 30 April 2013 Received in revised form 23 September 2013 Accepted 25 September 2013 Available online 3 October 2013 Keywords: Digestive enzymes Probiotic Brewer's spent yeast Species diversification Characterization of the major classes of digestive enzymes (amylase, protease and lipase) in the pyloric caeca and intestine of an omnivorous, white seabream (Diplodus sargus) and a carnivorous, meagre (Argyrosomus regius) fish species was assessed in response to dietary brewer's spent yeast (BSY, Saccharomyces pastorianus) supplementa- tion. For that purpose, three isonitrogenous (50%) and isolipidic (12%) diets were formulated: unsupplemented (control) or supplemented with BSY at 1 or 2%. White seabream exhibited lower proteolytic but higher amylase and lipase activities than meagre. In white seabream, BSY administration enhanced amylase and protease activities in the pyloric caeca and the intestine and lipase activity in the pyloric caeca, while in meagre, improvement on amylase activity in the pyloric caeca was observed with the 2% BSY diet. The results of the current study indicate that white seabream has higher ability to digest non-protein energy sources than meagre and that diet supplemen- tation with BSY improved digestive capacities in both species. © 2013 Elsevier B.V. All rights reserved. 1. Introduction In recent years, efforts for fish market expansion in the Mediterranean area have stimulated demand for new species to promote aquaculture diversification. Among potential new species, white seabream (Diplodus sargus) and meagre (Argyrosomus regius) were considered attractive candidates for fish culture diversification due to their high flesh quality and market prices, easy adaptation to captivity and production technol- ogy similar to that of other well established marine fish species (Basurco et al., 2011; Cárdenas, 2010; Monfort, 2010). Knowledge of nutritional requirements and specific aspects of physiology, namely the digestive capacity, is however essential for the development of adequate diet formulations and therefore for improvement of production under inten- sive culture conditions (Bakke et al., 2010; Caruso et al., 2009). Although still limited, data on the nutritional requirements of these species has accumulated recently. White seabream is known to have low dietary protein requirement and to efficiently use starch as energy source (Sá et al., 2007, 2008a,b), corroborating its reported omnivorous nature. Accordingly, Sá et al. (2007) showed that in white seabream dietary pro- tein to carbohydrate ratio could be reduced from 64:0 to 38:36 without impairing growth or feed utilization. On the other hand, meagre is carnivorous species, with a dietary protein requirement of 50% (Chatzifotis et al., 2012). Both species seem to tolerate moderate dietary lipid levels (up to 17%) (Chatzifotis et al., 2010, 2012; Sá et al., 2008a). Worldwide application of probiotics (live microbial dietary supple- ments) in aquafeed industry is increasing rapidly due to the described beneficial effects of these nutraceutics on several fish species (Balcázar et al., 2006; Irianto and Austin, 2002; Nayak, 2010; Oliva-Teles, 2012; Wang et al., 2008). Special emphasis has been given to the potential of probiotics in improving health and disease resistance in fish (Merrifield et al., 2010b; Suzer et al., 2008). With the increasing demands of modern aquaculture industry for high production and profits, probiotic potential in enhancing digestive function must not be overlooked (Merrifield et al., 2010b). At this regard, promising results have been published referring improved morphological properties and the proliferation capacity of mi- crovilli of the intestinal epithelium (JarmoŁowicz et al., 2012; Merrifield et al., 2010a; Sáenz de Rodrigáñez et al., 2009), promotion of intestinal maturation in larvae (Tovar-Ramírez et al., 2004; Waché et al., 2006) or increased digestive enzyme activity (Lazado et al., 2012; Wang and Xu, 2006). Overall, the effects of probiotics on fish digestive function would Aquaculture 416–417 (2013) 322–327 ⁎ Corresponding author at: Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, 4099-002 Porto, Portugal. Tel.: +351 22 340 1507; fax: +351 22 340 1511. E-mail address: carolinacastro23@gmail.com (C. Castro). 0044-8486/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquaculture.2013.09.042 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online