Fasting influences the muscle quality of fish during transportation by regulating the balance between energy metabolism and ammonia nitrogen stress

Abstract

Introduction

Fasting has been widely applied in aquaculture to improve the welfare of fish. However, fasting regulate the interplay of energy metabolism and ammonia nitrogen stress on the muscle quality unclear.

Objectives

To clarify the impact of fasting on the energy metabolism, ammonia nitrogen stress, and muscle quality.

Methods

Blunt snout bream (Megalobrama amblycephala) were fasted for different days before transportation. Then changes in energy metabolism, stress response, cell apoptosis, and muscle quality were assessed using UPLC-QTOF-MS untargeted metabolomics along with classical molecular biology techniques.

Results

Our findings revealed that short-term fasting (2–3 d) effectively alleviated ammonia nitrogen stress. The cortisol and superoxide dismutase decreased gradually as the fasting time was extended from 0 to 3 d, with decreased of 28.60 % and 55.39 %. Regarding the energy reserves, a reduction in muscle glycogen, protein, and lipid content was observed after fasting. These changes were attributed to the intensified tricarboxylic acid cycle, amino acid metabolism, and lipid metabolism. Furthermore, fasting enhanced the glycolysis of glycogen, and the gluconeogenesis of glutamic acid and aspartic acid to generate adenosine triphosphate. Notably, short-term fasting alleviated muscle cell apoptosis via down-regulating expression of Caspase 9 and Bax. Moreover, the water holding capacity, shear force, and springiness were better improved after fasting 2 d, reaching 79.88 %, 407.11 g, and 0.78 g, respectively. However, when fasting was extended to 4 d, there was a decrease in energy substances in the fish muscle and an increase in oxidative stress and apoptosis, thereby inducing a decrease in the muscle quality.

Conclusion

Our data concluded that fasting affects cell apoptosis by regulating the balance between energy metabolism and stress, ultimately impacting muscle quality. For long-distance transportation, a fasting period of 2–3 d is optimal.