Browsing by Author "Marques, Alexandra"
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- Comparative analysis between synthetic vitamin E and natural antioxidant sources from tomato, carrot and coriander in diets for market-sized dicentrarchus labraxPublication . Pereira, Ricardo; Costa, Mónica; Velasco, Cristina; Cunha, Luís M.; Lima, Rui C.; Baião, Luís F.; Batista, Sónia; Marques, Alexandra; Sá, Tiago; Campos, Débora A.; Pereira, Miguel; Jesus, Diva; Fernández-Boo, Sergio; Costas, Benjamin; Pintado, Manuela; Valente, Luisa M.P.Synthetic vitamin E is commonly used in aquafeeds to prevent oxidative stress in fish and delay feed and flesh oxidation during storage, but consumers’ preferences tend towards natural antioxidant sources. The potential of vegetable antioxidants-rich coproducts, dried tomato (TO), carrot (CA) and coriander (CO) was compared to that of synthetic vitamin E included in diets at either a regular (CTRL; 100 mg kg−1) or reinforced dose (VITE; 500 mg kg−1). Natural antioxidants were added at 2% to the CTRL. Mixes were then extruded and dried, generating five experimental diets that were fed to European sea bass juveniles (114 g) over 12 weeks. Vitamin E and carotenoid content of extruded diets showed signs of degradation. The experimental diets had very limited effects on fish growth or body composition, immunomodulatory response, muscle and liver antioxidant potential, organoleptic properties or consumer acceptance. Altogether, experimental findings suggest that neither a heightened inclusion dose of 500 mg kg−1 of vitamin E, nor a 2% inclusion of natural antioxidants provided additional antioxidant protection, compared to fish fed diets including the regular dose of 100 mg kg−1 of vitamin E.
- Exploring relations between social and emotional skills and bullying: the role of self-concept and empathyPublication . Veríssimo, Lurdes; Marques, Alexandra; Costa, Marisa; Castro, Isabel; Martins, Filipe; Miranda, FranciscaBullying in school has become a public health problem. Among the various bullying’s risk factors, the vulnerabilities associated with socio-emotional skills stand out. The present study aims to explore the relationship between bullying, victimization, selfconcept, and empathy; to test differences in victimization and bullying between boys and girls; and to study predictors of victimization and bullying. Participated 107 adolescents from 12 to 17 years old characterized by multiple family, social, and economic vulnerabilities. Three measures were used to assess empathy, self-concept, and bullying/victimization experience. The results show a significant negative correlation between victimization and all dimensions of self-concept. Bullying is only associated to popularity. There is no association between empathy and bullying or victimization. Girls significantly experienced more victimization than boys. Boys performed more bullying than girls. Self-concept is a significant predictor of victimization and bullying. Results are discussed in light of the socio-emotional skills paradigm and its power in preventing bullying.
- Use of technological processing of seaweed and microalgae as strategy to improve their apparent digestibility coefficients in European seabass (Dicentrarchus labrax) juvenilesPublication . Batista, Sónia; Pintado, Manuela; Marques, Alexandra; Abreu, Helena; Silva, Joana L; Jessen, Flemming; Valente, Luísa M.P.Algae are natural sources of nutrients, but the presence of anti-nutritional factors often compromises nutrient apparent digestibility coefficients (ADCs) in several fish species. In this study, physical-mechanical and enzymatic technological processing was applie to two seaweeds (Gracilaria gracilis and Ulva rigida) and three microalgae (Nannochloropsis oceanica, Chlorella vulgaris, and Tetraselmis sp.) in order to evaluate its effectiveness in improving nutrient ADC values in diets for European seabass. A practical commercial-based diet was used as reference (REF) and experimental diets were prepared by replacing 30% of REF diet with each test alga used either intact or after processing. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fast performance liquid chromatography (FPLC) analyses revealed that enzymatic processing was more effective than the physical one in changing the protein and peptides composition, increasing the amount of low-molecular-weight compounds in seaweeds and N. oceanica microalgae. Protein digestibility was significantly affected by algae species and in the case of the microalgae by the technological process. Gracilaria gracilis is better digested than U. rigida and physical processing enhanced protein and energy ADC values. Nannochloropsis oceanica and C. vulgaris are better digested than Tetraselmis sp.; the highest protein and energy ADCs were observed in diets containing enzymatically processed N. oceanica (NAN-ENZ) and physically processed C. vulgaris (CHLO-PHY), followed by the diet with physically processed Tetraselmis sp. (TETR-PHY). Results clearly showed that it is possible to increase nutrient accessibility and digestibility of algae by fish, by selecting the most adequate method to disrupt the cell wall. Moreover, the physical-mechanical and enzymatic technological processes used in this study are scalable to the industrial level.