Abstract

This study aimed to show the difference in compensatory growth (CG) with different starvation and feeding periods replications, depending on the IGF-I hormone level in the blood. There were 4 treatments in 3 replications. Other indexes like food coefficient ratio (FCR), specific growth rate (SGR) and daily food intake were also examined during the experiment. Fish were fed twice a day ad libitum as follows during the 65 days. Treatment A (TA): control treatment, continues feeding. Treatment B (TB):  4 weeks of starvation and 5 weeks of re-feeding. Treatment C (TC): 3 weeks of starvation and 5 weeks of re-feeding. Treatment D (TD): 2 weeks of starvation and 5 weeks of re-feeding. Each tank contained 23 fishes in each unit with an initial mean weight (SD) of 47.19 ± 0.42 (g). Blood was sampled in IGF-I hormone concentration at the beginning of the experiment, at the end of the starvation period and every 12 days in re-feeding periods. There was no significant difference between the treatments in FCR (P > 0.05). TB and TC had significant difference (P < 0.01) in comparison with other treatments in SGR, but no significant difference was observed among them (P > 0.05). IGF-I concentrations came down in comparison with control treatment at the end of the starvation period (Day 29) (P < 0.001), but no significant difference was observed among the treatments at the end of the re-feeding period (P > 0.05). According to the results, TB and TC showed more indexes of CG in comparison with TA and TD. Still IGF-I cannot show the quality of CG alone and other growth relating physiological elements in different feeding diets and regimes will be evaluated in future studies.

Key words: Compensatory growth, food coefficient ratio, food intake, IGF-I, rainbow trout, special growth ratio.