Effects of cold stress on juvenile Piaractus mesopotamicus and the mitigation by β-carotene

This study investigated the effects of cold stress on morphometrical and hematological biomarkers, energy metabolism, and oxidative stress in different tissues of P. mesopotamicus, and the protective role of beta-carotene. Fish were fed with a control diet (CD) and the same diet supplemented with 105 mg/kg beta-carotene (BD) for 60 days. After the feeding trial, fish fed CD or BD diets were exposed to control (24 degrees C) and low temperature (14 degrees C) for 24 h. Fish (CD and BD) exposed to thermal stress showed lower hepatosomatic index. The hemoglobin increased only in CD-fed fish exposed to 14 degrees C. Increased glycemia, plasmatic protein depletion, and decreased hepatic glycogen were observed in fish fed the CD, while only the lipid levels in liver were augmented in BD-fed fish exposed at 14 degrees C. Regarding the oxidative stress, increased antioxidant enzymes activity and lipid peroxidation were observed in CD-fed fish exposed to cold. The two-way ANOVA showed an interaction between dietary treatment and temperature for glucose and oxidative stress biomarkers, with the highest values recorded in 14 degrees C-exposed fish fed with the CD. Our study demonstrated that cold stress had the greatest impact on fish oxidative status, and p-carotene reduces harmful effects induced by cold in P. mesopotamicus.