Effects of exercise training on carbohydrate and lipid catabolism in the swimming muscles of Nile tilapia (Oreochromis niloticus)

Effects of flow velocity on the growth performance, antioxidant activity, immunity and intestinal health of Chinese Perch (Siniperca chuatsi) in recirculating aquaculture systems

The cultivation of Chinese Perch (Siniperca chuatsi) in recirculating aquaculture systems (RASs) has become a common trend. To explore the effect of flow velocity on the growth performance, antioxidant activity, immunity and intestinal health of Chinese Perch in RAS, 240 Chinese Perch with an initial weight of 70.66 ± 0.34 g were selected and randomly divided into 4 groups: control group [CK, 0 body length per second (bl/s)], low flow velocity (LF, 0.4 bl/s), middle flow velocity (MF, 0.8 bl/s) and high flow velocity (HF, 1.2 bl/s) for a 56-days experiment. The results showed that the flow velocity significantly increased the weight gain rate and feed intake in Chinese Perch. At 1.2 bl/s, the flow velocity increased the intestinal trypsin content and intestinal villus length. Furthermore, the relative expression of appetite-related genes showed a tendency to increase, and the relative expression of appetite-inhibiting genes had a significant decrease in HF. Regarding immune-related indicators, the activities of alanine aminotransferase (ALT) and aspartate transaminase (AST) were significantly higher in MF and HF. However, the activities of lysozyme (LZM) significantly decreased. Moreover, the activities of total superoxide dismutase (T-SOD) and catalase (CAT) were significantly higher in the CK group than in the other groups. Excessive flow velocity also caused the mRNA level of most immune-relevant genes to markedly decrease. With regard to intestinal health, the intestinal content sequencing results showed that MF could increase the intestinal diversity index of Chinese Perch. In addition, with increasing flow velocity, the relative abundance of Proteobacteria gradually increased, while the proportion of Firmicutes decreased. In conclusion, although the high flow velocity could promote growth, feeding, and digestion, inhibit fat deposition and increase the intestinal microbial abundance, the flow velocity caused stress, which leads to a decline in immunity and increases the death rate and the risk of intestinal disease in Chinese Perch. These findings provide theoretical support for the development of RASs for Chinese Perch.

Oral pyruvate prevents high-intensity interval exercise-induced metabolic acidosis in rats by promoting lactate dehydrogenase reaction

Introduction

There is no denying the clinical benefits of exogenous pyruvate in the treatment of pathological metabolic acidosis. However, whether it can prevent exercise physiological metabolic acidosis, delay the occurrence of exercise fatigue, and improve the beneficial effects of exercise and its internal mechanism remain unclear.

Methods

We randomly divided 24 male SD rats into 3 groups: one group was a control without exercise (CC, n = 8), and the other two groups were supplemented with 616 mg/kg/day pyruvate (EP, n = 8) or distilled water of equal volume (EC, n = 8). These groups completed acute high-intensity interval exercise (HIIE) after 7 days of supplementation. The acid metabolism variables were measured immediately after exercise including blood pH (pH_e), base excess (BE), HCO₃ ^-, blood lactic acid and skeletal muscle pH (pH_i). The redox state was determined by measuring the oxidized coenzyme I/reduced coenzyme I (nicotinamide adenine dinucleotide [NAD⁺]/reduced NAD⁺ [NADH]) ratio and lactate/pyruvate (L/P) ratio. In addition, the activities of lactate dehydrogenase A (LDHA), hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) were determined by ELISA.

Results

Pyruvate supplementation significantly reversed the decrease of pHe, BE, HCO₃ ^- and pH_i values after HIIE (p < 0.001), while significantly increased the activities of LDHA (p = 0.048), HK (p = 0.006), and PFK (p = 0.047). Compared with the CC, the NAD+/NADH (p = 0.008) ratio and the activities of LDHA (p = 0.002), HK (p < 0.001), PFK (p < 0.001), and PK (p = 0.006) were significantly improved in EP group.

Discussion

This study provides compelling evidence that oral pyruvate attenuates HIIE-induced intracellular and extracellular acidification, possibly due to increased activity of LDHA, which promotes the absorption of H⁺ in the LDH reaction. The beneficial effects of improving the redox state and glycolysis rate were also shown. Our results suggest that pyruvate can be used as an oral nutritional supplement to buffer HIIE induced metabolic acidosis.

Effects of sustained swimming exercise on growth and body composition responses of Nile tilapia (Oreochromis niloticus), red drum (Sciaenops ocellatus), and hybrid striped bass (Morone chrysops × M. saxatilis)

Exercise has been shown to increase growth of many salmonid species. However, limited research has evaluated exercise on warmwater species. The present study was conducted to evaluate with tilapia, red drum (RD), and hybrid striped bass (HSB), the effects of swimming (exercising) in a constant slow current of approximately one body length/s (1bl/s) compared to not being forced to swim in a static culture system. Concurrent trials were conducted with 22 advanced juvenile male Nile tilapia (Wt₀ 97.9 ± 2.4 g), 38 juvenile red drum (Wt₀ 74.9 ± 4.4 g), and 20 juvenile HSB (Wt₀ 78.0 ± 3.2 g). Equal numbers of fish of each species were pit tagged and randomly assigned to two tanks, one operated static (control) and the other with current (exercised), which were all part of the same recirculating aquaculture system. Fish were fed to satiation twice daily a commercial diet and individually weighed every 2 weeks through 7 weeks. Significant (P ≤ 0.05) enhancements of weight gain were observed for exercised tilapia and RD vs static (control) treatments. Reduced growth was observed in exercised HSB, possibly due to consistently skittish feeding behavior. Hepatosomatic index was lower in all exercised fish, though not significantly so for RD and tilapia. Significant reductions also were detected in liver glycogen of exercised tilapia and RD. Results from this study indicate that continuous exercise beneficially affected aspects of tilapia and red drum growth and altered their body composition.

Differences in swimming ability and its response to starvation among male and female Gambusia affinis

To explore the differences in the swimming ability and environmental adaptive abilities between male and female Gambusia affinis, we assessed the differences in burst swimming speeds (U_burst), critical swimming speeds (U_crit) and their related fin areas, and consumption of energy substances after starvation at 0 (control group), 15, 30, 45, and 60 days, respectively. The results showed that the pectoral and caudal fin areas did not differ significantly between male and female G. affinis. However, the dry mass, condition factors, and absolute contents of glycogen, lipids, and proteins were significantly elevated in females in the control group (P<0.05), whereas U_burst and U_crit were significantly low (P<0.05). After starvation of 60 days, the rate of consumption of lipids was significantly low in the females (P<0.05). Although U_burst and U_crit decreased linearly with increased duration of starvation, the coefficient of linear equation between U_crit and starvation time was significantly lower in females than males (P<0.05). These findings indicated that low body mass and condition factors reduce the relative bear load and moving resistance that causes high swimming performance in male G. affinis. High contents of energy substances and low rate of consumption of lipids result in stable U_crit in females during hunger.

Summary: The study explored the causes of variation in swimming performance with respect to morphological and physiological characteristics, which provides further information about environmental adaptive ability in Gambusia affinis.