Aquaculture Europe 2023

September 18 - 21, 2023


Add To Calendar 20/09/2023 16:15:0020/09/2023 16:30:00Europe/ViennaAquaculture Europe 2023HYDROXYTYROSOL-RICH EXTRACT FROM OLIVE JUICE AS AN ADDITIVE IN GILTHEAD SEA BREAM FED A HIGH FAT DIET AND WITH FOOD RESTRICTION: DIGESTIVE ENZYME ACTIVITYStolz 1The European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982


I . García-Meilán*1 , G. Puig-Valero1, S. Balbuena-Pecino1, M. Montblanch1, R. Fontanillas 2, J. Gutiérrez1 ,  E. Capilla1, I. Navarro1, and A. Gallardo 1


1 Departament de Biologia Cel·lular, Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona, Diagonal 643, 08028, Barcelona, Spain.

2 Skretting Aquaculture Research Centre (ARC), Sjøhagen 3, Stavanger, Norway.




Increasing  inclusion of plant-based products and highly lipid  commercial diets due to the elevated cost of fish meal highlights the need of the sustainable development of aquaculture through the formulation of functional diets .  In this sense,  olive (Olea europaea ) juice extract incorporation in aquafeeds  has been found to enhance  immune properties, gut health and functionality, and somatic growth (Gisbert et al., 2017; Rong et al., 2020) , possibly due to  the presence  of  bioactive  compounds such as phenols , mainly hydroxytyrosol, which has anti-obesogenic properties (Lutfi et al., 2017) .

 The aim of this study was to evaluate  the digestive process in gilthead sea bream ( Sparus aurata) fed a high-fat diet , administered at two rations, ad libitum or restricted, and to test the effects of an olive juice extract rich in hydroxytyrosol as an additive .

Materials and methods

 Gilthead sea bream juveniles ( ±  80.8 g)  were acclimated to the animal facilities of the Faculty of Biology at the University of Barcelona (Spain). An experimental high-fat diet (24% lipids, 47% protein and 23 MJ/kg of digestible energy ) was formulated and produced by Skretting ARC (Stavanger, Norway). The diet was produced in the absence (HF) or presence (HF-HT) of an  olive hydroxytyrosol -rich extract (HIDROX®, 1.66% )  provided by Oliphenol LLC. (Hayward, CA, USA). To establish two different conditions in terms of energy intake, the diets were administered at ad libitum (1.8 %  of body weight (BW)  in the morning and 1.2% in the afternoon), or at restricted  ration (1. 8%  of BW only in the morning ,  named R-HF and R-HF-HT groups). After 8 weeks of growth, samples of pyloric caeca (PC) and proximal intestine (PI) were obtained from nine animals per condition and time, just before feeding in the morning and at 5h post-feeding. Samples  were directly frozen in liquid nitrogen and stored at 80 ºC for later analysis.  Intestinal pH was measured,  and after sample homogenization, t he activity of digestive enzymes (alkaline protease, α-amylase, and lipase) and the  trypsin/chymotrypsin ratio were analyzed.

Results and Discussion

 No  significant  differences were found in growth  between the  HF and HF-HT groups, whereas food restriction significantly diminished it (-22.1%) (Balbuena-Pecino et al., 2023) . Regarding digestive enzyme activities (Figure 1),  higher levels were found in PC before feeding,  as  pancreatic enzymes  can be released  in this intestinal region  prior to  food  intake to improve  the digestive process . Conversely, 5h after feeding, the highest digestive activity was found in PI, where  the  digestion was taking place. When comparing HF  and R-HF groups,  in PC,  a  significant  reduction  in α -amylase activity was observed in PC, both anticipatory and 5h post-feeding,  and lipase anticipatory activity was also down-regulated. However, both groups showed similar enzyme activities  in PI . HYDROX addition  to the  high-fat diet  tended to up- regulate the anticipatory activity  of α- amylase in PC ,  and alkaline protease, α- amylase, and lipase  activities  in PI. In addition, it also increased the digestive activity at 5h post-feeding in the PC for all the enzymes studied. Finally,  R-HF-HT fish  showed the highest  PC  lipase  anticipatory activity and  an intermediate α- amylase activity  between R-HF  and HF -HT fish  in  both intestinal segments  before feeding , as well as  at 5h post-feeding in PC. Additionally , both restricted ration groups presented  similar  alkaline protease  activity  in PI  before feeding.


 Food restriction promoted an optimization of the digestive function in fish, leading to  relatively good growth performance despite a reduction in food intake. The observed  growth reduction  was  less  than what would be  expected with a  40% food restriction .  On the other hand, the effect of HT needs further studies  as the observed  increase in anticipatory activities suggests in general an adjustment of the digestive function to optimize the  use of the given diet.


Balbuena-Pecino et al., (2023).  Front. Physiol . 13: 966175. doi: 10.3389/fphys.2022.966175

 Gisbert et al., (2017).  Br. J. Nutr. 117, 351-363. doi: 10.1017/S0007114517000228

Lutfi et al., (2017). PLos One 12 , e0178833. doi:10.1371/journal.pone.0178833

Rong , et al., (2020).  J. Ocean . Univ. China 19, 428438. doi:10.1007/s11802-020-4232-8