عنوان مقاله [English]
The objective of this study was to evaluate the effect of recombinant bovine somatotropin 1% (Eltosil®) on growth performance in rainbow trout. 1200 rainbow trout (Oncorhynchus mykiss) weighing 0.5±0.05 gram were randomly distributed in two groups 1) the control group and 2) Eltosil® group, each in three replications. These fishes were randomly divided in six 100 liter square troughs with a continuous water flow of 1 liter per minute. Troughs were supplied with a well water (temperature range: 15±1ºC, O2: 7.2±0.2mg/l, pH= 8±0.3). In this research, the fish received of 200g Eltosil® per 100kg BW. The administration method of Eltosil®-mixed feed to fish was once a week for 4 consecutive weeks at each treatment stage, totally 8 times for 12 weeks (once a week, 4 times in the first step, withdrawal for four weeks in the second step, once a week for 4 times in the third step). To calculate growth factors, fish were weighed weekly and their body lengths were measured every two weeks (before and after each experiment). At the end of each rearing period (on day 28, 56, 84) the means of whole body weight, weight gain, average daily growth, total length, average daily length, grams of weight gain per gram of food, specific growth rate, condition factor, food conversion rate, and the percentage of survival ratio were calculated in the control and Eltosil® groups. Moreover, at the end of rearing period (on day 84), comparative growth rate was calculated. The results of this study demonstrated that there were no significant differences between growth factors in the control and Eltosil® groups on days 28, 56, 84 of rearing periods (P>0.05). These results show that oral administration of recombinant bovine somatotropin (Eltosil®) was not a suitable way to increase rapid growth in rainbow trout weighing 0.5±0.05 gram.