Effects of Fasting on Intermediary Metabolism Enzymes in the Liver and Muscle of Rainbow Trout

Fish can go through periods of feed deprivation, either due to natural causes influenced by temperature or management techniques in animal production, affecting their energy metabolism differently, depending on the duration of fasting in days and water temperature. This study showed the effect of different days of fasting before slaughter in rainbow trout by analyzing the intermediary metabolic enzymes in the muscle and liver. For this purpose, a non-fasting group was compared with trout that fasted for 5, 10, and 20 days (55, 107, and 200 degree days (degrees C d), respectively). A first phase of increased activity of enzymes involved in glycolysis was observed, increasing hexokinase enzyme activity in muscle and pyruvate kinase enzyme activity in muscle and liver. As the fasting days progressed, enzymes involved in the gluconeogenic and glycogenolytic pathways in the liver such as lactate dehydrogenase and glycogen phosphorylase increased their activity regarding the no fasted group. After 20 days of fasting (200 degrees C d), lipogenic and protein related enzyme activity depletion was observed, leading to significant changes in energy metabolism. Therefore, prolonged fasting with high degree days duration may compromise the energy supply for the vital development of rainbow trout.

Automated summary

Fish can experience periods of feed deprivation due to natural causes or management techniques in animal production. This study analyzed the effects of different fasting durations on rainbow trout's energy metabolism by studying metabolic enzymes in muscle and liver. Results showed increased activity of glycolytic enzymes in the early fasting phase, while enzymes involved in gluconeogenesis and glycogenolysis increased their activity as fasting days progressed. After 20 days of fasting, lipogenic and protein related enzyme activity depletion was observed, leading to significant changes in energy metabolism. Thus, prolonged fasting with high degree days duration can compromise the energy supply for rainbow trout's development.