Nutritional nano-selenium inclusion in fishmeal-free plant-based diets enhances stress resistance and post-stress recovery of common carp (Cyprinus carpio)

Abstract

The purpose of this investigation was to study how supplementing nutritional nano-selenium (NNSe) in diets containing all-plant-protein (APP) ingredients affects the physiological properties associated with stress resistance and post-stress recovery in common carp (Cyprinus carpio). Therefore, two basal diets with equal crude protein content were formulated: the FM-Control diet contained 35 % fishmeal (FM), and the APP-Control diet contained merely plant-protein constituents. Three additional diets were also prepared by supplementing NNSe in the APP-Control diet at levels of 1 (NNSe1), 2 (NNSe2), and 3 (NNSe3) mg/Kg. One hundred and fifty fish (average weight, 30.63 ± 0.61 g) were randomly allocated to five groups in triplicate tanks and fed the experimental diets for 60 days. The best growth performance and feed efficiency (FE) among the NNSe-supplemented groups were recorded in the NNSe3 and FM-Control groups (P < 0.05). The highest liver glutathione peroxidase (GPx) activity was detected in the FM-Control group, followed by the NNSe3 group (P < 0.05). Also, the highest and lowest liver malondialdehyde (MDA) contents were found in the FM-Control and the NNSe3 groups, respectively (P < 0.05). Following the 60-day feeding trial, the fish were challenged with acute crowding stress by reducing water volume to confine fish at the density of 200 kg/m3 for 45 min, and their blood samples were obtained at 0, 2, 4, 8, 12, and 24 h after stress to compare post-stress recovery between different groups. At most time intervals after stress, plasma levels of cortisol, glucose, lactate, alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) of the NNSe3 group were equal to or lower than values measured for the FM-Control group. The results suggest that NNSe at 3 mg/Kg enhances stress resistance and post-stress recovery in carp fed all-plant-protein diets.

Keywords

• Aminotransferases
• Antioxidant defense
• Cortisol
• Glucose
• Stress challenge