Inês Guerreiro

Effects of temperature and dietary protein level on hepatic oxidative status of Senegalese sole juveniles (Solea senegalensis)

Effects of 55 and 45% dietary protein levels (55P and 45P diets, respectively) and temperature (12 and 18 °C) on hepatic activity of superoxide dismutase (SOD), catalase, glutathione peroxidase, glutathione reductase (GR), glucose-6-phosphate dehydrogenase and lipid peroxidation (LPO) levels of Solea senegalensis juveniles were studied. Further, effects of acute thermal shocks provoked by a drop (18 °C to 12 °C) or a rise (12 °C to 18 °C) of water temperature on sole oxidative state was also evaluated. Dietary protein reduction increased LPO levels though no major alterations were found on antioxidant enzyme activities between dietary treatments. At 12 °C GR activity was higher and SOD activity was lower than 18 °C but LPO levels were not affected. In both thermal shock cases, LPO levels increased in 55P group, probably due to insufficient antioxidant enzyme activation. In contrast, fish of 45P group under acute exposition to warmer and colder temperature exhibited no substantial changes and a significant decrease on LPO levels, respectively, along with no major changes in antioxidant enzymes. Overall, results suggest that independently of rearing temperatures 45P group was more susceptible to oxidative stress than 55P group. Thermal shock either due to rise or drop of temperature seemed to induce oxidative stress in 55P group.

Prebiotics effect on immune and hepatic oxidative status and gut morphology of white sea bream (Diplodus sargus)

The aim of this study was to evaluate the effects of short-chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS) and galactooligosaccharides (GOS) on immune and hepatic oxidative status, and gut morphology of white sea bream juveniles. Four diets were formulated: a control diet with fish meal (FM) and plant feedstuffs (PF) (30FM:70PF) and three test diets similar to the control but supplemented with 1% of scFOS, XOS or GOS. Dietary prebiotic incorporation did not affect total blood cell counts, hematocrit, hemoglobin, red blood indices or differential white blood cell counts. Fish fed GOS had lower ACH50 and nitric oxide than fish fed control diet. XOS enhanced immune status through the increase in alternative complement pathway (ACH50), lysozyme and total immunoglobulin. The higher activity of glucose 6-phosphate dehydrogenase in fish fed FOS compared to the other dietary groups was the only related antioxidant enzyme affected by prebiotics in the liver. GOS ameliorated the precocious adverse effects of PF based diet on gut histomorphology, as denoted by the lower incidence of histological alterations in fish fed GOS for 15 days. In conclusion, XOS and GOS at 1% might have potential to be used as prebiotics in white sea bream juveniles.

Effect of temperature and short chain fructooligosaccharides supplementation on the hepatic oxidative status and immune response of turbot (Scophthalmus maximus).

In this study the effect of diet supplementation with different levels of short-chain fructooligosaccharides (scFOS) on the hepatic oxidative status, hematology and innate immune parameters was evaluated in turbot reared at 15 °C and 20 °C. Four practical diets containing half of the protein provided by plant ingredients and the other half by fish meal were supplemented with scFOS at 0%, 0.5%, 1.0% and 2.0% and fed to turbot juveniles for 9 weeks. Independently of the rearing temperature, diet with 1% scFOS increased the haematocrit (Ht) while 2% scFOS augmented the mean corpuscular haemoglobin concentration (MCHC). Mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), white blood cells (%) and lysozyme were higher in fish reared at 15 °C, whereas red blood cells and neutrophil numbers increased in fish reared at 20 °C. Catalase (CAT) and glutathione peroxidase (GPX) activities were affected by rearing temperature being lower in fish reared at 20 °C. Compared to the control diet, at 15 °C, turbot fed 0.5 or 1% scFOS presented lower activities of CAT and glutathione reductase (GR). At 20 °C turbot fed the 2% scFOS diet presented lower activities of CAT and GPX. Lipid peroxidation (LPO) and glucose 6-phosphate dehydrogenase (G6PDH) activity were not affected by temperature nor dietary prebiotic incorporation. Results of this study suggest scFOS has no effect on innate immunology or hematology. High temperature (20 °C) does not induce turbot oxidative stress, but the recommended dietary scFOS incorporation level for counteracting oxidative stress may differ with other rearing temperature.

Gut morphology and hepatic oxidative status of European sea bass ( Dicentrarchus labrax ) juveniles fed plant feedstuffs or fishmeal-based diets supplemented with short-chain fructo-oligosaccharides and xylo-oligosaccharides

The effects of short-chain fructo-oligosaccharides (scFOS) and xylo-oligosaccharides (XOS) on gut morphology and hepatic oxidative status were studied in European sea bass juveniles weighing 60 g. Fish were fed diets including fishmeal (FM diets) or plant feedstuffs (PF diets; 30 FM:70 PF) as main protein sources (control diets). Four other diets were formulated similar to the control diets but including 1 % scFOS or 1 % XOS. At the end of the trial, fish fed PF-based diets presented histomorphological alterations in the distal intestine, whereas only transient alterations were observed in the pyloric caeca. Comparatively to fish fed FM-based diets, fish fed PF diets had higher liver lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) activities, and lower glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase activities. In fish fed the PF diets, prebiotic supplementation decreased SOD activity and XOS supplementation further decreased CAT activity. In fish fed the FM diets, XOS supplementation promoted a reduction of all antioxidant enzyme activities. Overall, dietary XOS and scFOS supplementation had only minor effects on gut morphology or LPO levels. However, dietary XOS reduced antioxidant enzymatic activity in both PF and FM diets, which indicate a positive effect on reduction of hepatic reactive oxygen species production.