Effect of confinement stress on rainb ow trout (Oncorhynchus mykiss) juvenile fed on spirulina platensis extract

Aquaculture in enclosed spaces ha s negatively affected the health of fish resu lting in increased susceptibility to diseases and stress (1).Due to the restrictions placed on th e use of chemicals such as antibiotics and ho rmones in feeding aquatic animals, which will be later consumed by humans, the use of na tural substances such as those derived from plant and algae in fish food processing has been increased (2). The purpose of this study was to ev aluate the physiological responses of Rainbow trout fed on diets supplemented with methano lic extract of Spirulina platensis. 150 fish with a mean initial weight of 12.6±0.3 g were randomly divided into five groups.The juveniles were fed for 8 weeks with the diets containin g 0 (T1), 250 (T2), 500 (T3), 1000 (T4) and 2 500 (T5) mg of Spirulina extract per kg of di et. At the end of experiment, fish were kept outside the water for 30 seconds (air exposure stress). Then, they were transferred in small b askets in water for one hour (increasing fish density from 10 g L-1 to 100 g L-1) as a con finement stress (3). Then blood plasma was st ored at -20 ºC for glucose and cortisol measurem ents. The results showed that three hours after the air exposure and confinement stress, m inimum (2.42 mg dl-1) and maximum (6.18 ± 2.5 mg dl-1) levels of plasma cortisol were obs erved in 2500 and 500 mg kg-1 treatments, re spectively. Moreover, the minimum and maximum level of glucose was observed in 0 and 500 mg kg-1 treatments, respectively. After eig ht hours, Plasma cortisol and glucose showed the highest level in 500 mg kg-1 treatment. T herefore, based on the results, it can be sugge sted that adding 250 mg/ kg of Spirulina extract to the diet can reduce stress in juvenile rainbow trout especially handling stress.

Aquaculture in enclosed spaces ha s negatively affected the health of fish resu lting in increased susceptibility to diseases and stress (1).Due to the restrictions placed on th e use of chemicals such as antibiotics and ho rmones in feeding aquatic animals, which will be later consumed by humans, the use of na tural substances such as those derived from plant and algae in fish food processing has been increased (2). The purpose of this study was to ev aluate the physiological responses of Rainbow trout fed on diets supplemented with methano lic extract of Spirulina platensis. 150 fish with a mean initial weight of 12.6±0.3 g were randomly divided into five groups.The juveniles were fed for 8 weeks with the diets containin g 0 (T1), 250 (T2), 500 (T3), 1000 (T4) and 2 500 (T5) mg of Spirulina extract per kg of di et. At the end of experiment, fish were kept outside the water for 30 seconds (air exposure stress). Then, they were transferred in small b askets in water for one hour (increasing fish density from 10 g L-1 to 100 g L-1) as a con finement stress (3). Then blood plasma was st ored at -20 ºC for glucose and cortisol measurem ents. The results showed that three hours after the air exposure and confinement stress, m inimum (2.42 mg dl-1) and maximum (6.18 ± 2.5 mg dl-1) levels of plasma cortisol were obs erved in 2500 and 500 mg kg-1 treatments, re spectively. Moreover, the minimum and maximum level of glucose was observed in 0 and 500 mg kg-1 treatments, respectively. After eig ht hours, Plasma cortisol and glucose showed the highest level in 500 mg kg-1 treatment. T herefore, based on the results, it can be sugge sted that adding 250 mg/ kg of Spirulina extract to the diet can reduce stress in juvenile rainbow trout especially handling stress.