Influence of Physical Activity and Nutritional Limitation on Amino Acid, Fatty Acid Metabolism, and Biochemical Responses in Juvenile Rainbow Trout (Oncorhynchus mykiss, Walbaum, 1792)

Abstract

This study investigates the synergistic effects of swimming activity and dietary restriction on the metabolic and nutritional characteristics of muscle tissue in juvenile rainbow trout (Oncorhynchus mykiss, Walbaum, 1792). During a 6-week study, four groups of juvenile rainbow trout, each starting with an average weight of 26.54 ± 0.36 g, were analyzed: the first group was allowed to feed freely in static water (SW group), the second experienced a dietary limitation (25% feed restriction) (LF group), the third was required to swim at a speed of one body length per second (SE group), and the fourth group faced a combination of dietary restriction (25% feed restriction) and enforced swimming activity (SELF group). Swimming activity was implemented using a water flow rate of one body length per second (1 BL s⁻¹), ensuring a standardized exercise intensity. Comprehensive analysis revealed significant alterations in biochemical parameters, amino acid composition, and fatty acid profiles in rainbow trout muscle tissue. The results indicate a decrease in histidine levels (p  < 0.05) with the combined effect of both swimming and feeding restrictions. Additionally, cysteine and semi-essential amino acids (EAAs) showed a decrease (p  < 0.05) solely due to the influence of swimming. As for fatty acid outcomes, linolenic acid exhibited a reduction with the combined impact of both swimming and feeding restrictions (p  < 0.05), while margaric acid significantly decreased (p  < 0.05) only with the influence of swimming. Crucial shifts in antioxidant defense mechanisms, including glutathione (GSH) and lipid peroxidation (LPO) levels, were identified, highlighting the roles of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) as biochemical parameters. Detailed examination further clarified modifications in glucose-6-phosphate dehydrogenase (G6PD) activities, reactive oxygen species (ROS) levels, and lactate dehydrogenase (LDH) activity, serving as pivotal indicators of oxidative stress and tissue damage. These findings contribute to a holistic understanding of nutritional dynamics within rainbow trout muscle tissue, offering insights crucial for optimizing fish health and productivity in aquaculture.