This study was designed to examine the protective effects of the extract of mulberry (Morus alba L.) leaves (EML) on crucian carp (Carassius auratus) against a high stocking density, Cu exposure and trichlorfon exposure, which adversely impact fish growth performance, feed intake and fish locomotion. High stocking densities decreased the activities of amylase, lipase, trypsin, Na⁺/K⁺-ATPase and alkaline phosphatase (AKP), and increased the content of malonaldehyde (MDA) in fish digestive organs, indicating an impairment of the digestive function and a disturbance of the antioxidant status. Cu exposure increased the activities of glutamate–oxaloacetate transaminase (GOT) and glutamate–pyruvate transaminase (GPT) in fish digestive organs, suggesting the activation of amino acid metabolism. Furthermore, trichlorfon exposure reduced the activities of lactate dehydrogenase (LDH), glutathione reductase (GR), GOT and GPT, and the capacities of the anti-superoxide anion (ASA) and anti-hydroxyl radical (AHR) in fish muscles, indicating a disruption of the bioenergetic homeostasis and antioxidant status. Our present study indicates that dietary EML supplementation relieved the detrimental effects induced by these stressors.

The study explored the effects of Angelica sinensis extract (AsE) on oxidative lesions and apoptosis in branchiae and red blood corpuscles in hypoxia–reoxygenation (HR) and Cu-treated carp (Cyprinus carpio var. Jian). After feeding trial for 30 days, the carp were exposed to HR and CuSO₄. The results indicated that dietary AsE increased the durative time, decreased the oxygen consumption rate, suppressed ROS generation and cellular component oxidation, decreased enzymatic antioxidant activity and reduced glutathione (GSH) levels in red blood corpuscles and branchiae in carp under hypoxia. Moreover, dietary AsE avoided the loss of Na⁺,K⁺-ATPase, metabolic and antioxidant enzyme activities, ROS generation and cellular component oxidation, as well as the increase in caspase-8, 9, and 3 activities in the branchiae of the carp and inhibited ROS generation. It furthermore avoided the loss of Na⁺,K⁺-ATPase and metabolic enzyme activities, the decrease in GSH levels and hemoglobin content, the increase in the activities of caspase-8, 9, and 3 and the increase in the levels of cytochrome c and phosphatidylserine exposure in the red blood corpuscles of Cu-exposed carp. The present results suggested that dietary AsE improved hypoxia tolerance and inhibited HR or Cu-triggered oxidative lesions and apoptosis. Therefore, AsE can be utilized as a natural inhibitor of Cu and HR stress in fish.

Firstly, a linoleic and linolenic acid emulsion were incubated with petroleum ether extract, ethyl acetate extract (EAE), ethanol extract and aqueous extract of Ginkgo biloba leaves. The flavonoids content, total antioxidant capacity (T-AOC) and metal-chelating ability (MCA) were determined in EGbs above. Results showed that the extracts of Ginkgo biloba leaves (EGbs) inhibited the lipid oxidation in material above. Of all of EGbs, EAE showed the strongest T-AOC, MCA and protective effects against the lipid oxidation. Next, fish feeds were incubated with graded levels of EAE. The results showed that EAE inhibited lipid oxidation in fish feeds. The optimal inclusion levels of EAE for minimizing lipid oxidation were 4.26 g kg⁻¹ feeds. The effect of EGbs on the lipid oxidation may be closely associated with their flavonoid content. Finally, juvenile carp (14.8 ± 0.4 g) were fed with EAE at concentrations ranging from 0.0 to 6.0 g kg⁻¹ for 60 days. Current data displayed that dietary EAE increased the growth performance of fish. This result of EAE may be ascribed to its enhancing effect on the activity of digestive and absorptive enzymes and antioxidant capacity in digestive organs of fish. Furthermore, dietary EAE decreased the hot-drying-induced lipid oxidation in fish meat through inhibiting the induction effect of hemoglobin in erythrocytes. Our study suggests that EGb can be considered as a potential natural antioxidant for fish and fish feed.

The objective of this study was to investigate the effects of Scoparia dulcis extract (SDE) on stress induced by high stocking density and Cu and trichlorfon exposure in crucian carp (Carassius auratus). The results showed that these stressors exerted detrimental effects in fish, such as inhibition of growth performance, reduced feed intake, and interruption of fish locomotion. Under high stocking density, dietary SDE supplementation increased the content of reduced glutathione (GSH) and the activities of amylase, catalase (CAT), and glutathione reductase (GR) and decreased the content of malonaldehyde (MDA) in the intestine of crucian carp. A similar trend was presented in the hepatopancreas under Cu exposure. Dietary SDE supplementation enhanced the activities of CAT, superoxide dismutase (SOD), glutathione peroxidase (GPx), lactate dehydrogenase, glutamate-oxaloacetate transaminase, and glutamate-pyruvate transaminase in the muscle of crucian carp under trichlorfon exposure. The optimum dietary SDE supplementation levels were 4.07, 4.33, and 3.95 g kg⁻¹ diet based on the recovery rate of weight gain (RWG), feed intake (FI), and inhibitory rate of rollover (IR) for crucian carp under high stocking density and Cu and trichlorfon exposure, respectively. Overall, dietary supplementation with SDE may be a useful nutritional strategy for relieving these stresses in aquatic animals.

The goal of this study is to assess how dietary Atractylodes lancea ultrafine powder (AUP) affects crucian carp (Carassius auratus) growth, body composition, and hypoxia tolerance. A total of 630 crucian carp (13.21 ± 0.17 g) were fed diets containing 0.0%, 3.0%, 6.0%, 9.0%, 12.0%, 15.0%, and 18.0% AUP for 15 days. In crucian carp, dietary AUP was observed to improve protein content and decrease weight gain and fat content (p < 0.05). The ideal AUP addition level for fish was 13.04%, based on broken-line regression analysis of the protein concentration in fish bodies. The tissues and organs of crucian carp showed increased enzymatic antioxidant activities and non-enzymatic antioxidant levels, indicating that dietary AUP reduced the production of reactive oxygen species (ROS) and inhibited lipid oxidation (p < 0.05). This study shows that dietary AUP has a significant anti-obesity impact in fish, which is strongly linked to boosting the anabolism of protein and antioxidant defense as well as improving glucose metabolism to reduce glucose as the raw material for body fat synthesis. Additionally, under hypoxic conditions, the addition of AUP increased duration time (DT) and decreased crucian carp oxygen consumption rate (p < 0.05). The DT broken-line regression study verified that 6.05% is the ideal AUP level for fish. According to our research, dietary AUP strengthens fish’s resistance to hypoxia by modifying the metabolism of proteins and carbohydrates for energy production and enhancing antioxidant defense in respiration-related tissues and organs. In conclusion, AUP may be a natural way to reduce fish obesity and hypoxic stress.

This study aimed to assess how dietary water extract of Aloe vera peel (WEA) affected biochemical markers and hypoxia tolerance in Jian carp (Cyprinus carpio var. Jian). 630 Jian carp (11.77 ± 0.10 g) were fed diets with increasing WEA concentrations (0.0–1.8%) for 15 days. The results showed that short-term feeding of WEA enhanced carp growth performance (p < 0.05). When WEA was added to diets in hypoxic conditions, carp’s duration time (DT) increased and their oxygen consumption rate (OCR) decreased (p < 0.05). In carp blood, feeding WEA improved hematological parameters, such as hematocrit, hemoglobin concentration, mean corpuscular volume, and mean corpuscular hemoglobin content, (p < 0.05) and decreased plasma ammonia levels. Lactic dehydrogenase levels in muscles and gills and transaminases (GOT and GPT) in red blood cells, gills, and hepatopancreas were significantly higher in carp fed diets containing WEA (p < 0.05). Additionally, dietary WEA decreased ROS generation and lipid oxidation in carp respiratory-related tissues and cells by raising both enzymatic antioxidant activities and non-enzymatic antioxidant levels (p < 0.05). Finally, dietary WEA increases hypoxia tolerance in carp by modifying protein and carbohydrate metabolism and boosting the antioxidant capacity of respiratory-related tissues and cells, suggesting that WEA may be a natural method of lowering hypoxic stress in fish.