Effect of Different Photoperiod and Compensatory Growth on Growth, Immunology and Hematology in rainbow trout (Oncorhynchus mykiss)

In this study the combined effects of photoperiod and compensatory growth on growth, hematology indexes, biochemical indexes, cortisol and lysozyme of rainbow trout were investigated. In this regard, 552 specimens of rainbow trout fingerlings )8± 0/9gr (were treated with different photoperiod regimes (LD 06:18, LD 12:12, LD 18:06, and LD 24:00) with intermittent periods of satiety and starvation (4 days starvation and 4 days refeeding for 60 days) in compared to control groups. In photoperiod regimes 24 h light had the highest growth and food intake efficiency, but 6 h light treatment with compensatory growth had the lowest feed conversion ratio in compare to other treatments. The 4 days of starvation reduced amount of biochemical parameters and the light did not cause any changes in these parameters. In terms of 24 h of light regime, Hct (33/04%), Hb (9/43g dL-1) and RBC (1/31*106Ml-1) amounts were significantly higher than other treatments, but lysozyme level was not affected by light and starvation treatments. Also, cortisol levels during starvation (4 days) were significantly higher than 4 days refeeding. According to the results, the treatment of 6h of light in both photoperiod techniques alone and the combination of photoperiod with compensatory growth was determined as the optimal treatment.