No abstract

Summary The present study investigated the interaction of feeding times with two dietary fat levels on physiological responses to handling stress in juvenile Beluga sturgeon. Fish were fed with two different diets (high energy; HE: 24% fat and low energy; LE: 12% fat) for 8 weeks at two feeding times; 09:00 and 16:00 (during the day) or 21:00 and 04:00 (during the night). At the end of the trial, blood samples were taken and the resting fish were held in a net out of water for 90 s as the handling stressor. Three hours after application of stress, post‐stress blood was taken. Cortisol, glucose, and lactate concentrations were considered as stress indicators. The mean values of cortisol and lactate levels did not reveal a significant difference between pre‐ and 3‐hr post‐stress samples, but the average concentration of glucose showed a significant difference. Cortisol, lactate and glucose concentrations were not influenced by the difference in the diets. Moreover, the cortisol and lactate concentrations were not affected by the different feeding times, while glucose levels were significantly affected by the feeding times with the lowest level in fish fed during the day. With respect to stress indicators, the results revealed that feeding times affected pre‐ and post‐stress secondary response to handling stress, but the rate and magnitude of metabolites (cortisol, glucose and lactate) were not affected by dietary fat levels. Therefore, it is necessary to examine the best feeding times with the interaction of feed ingredients in sturgeon farming.