The effects of short-term growth hormone (somatotropin) bath on some growth and immunity indices in the early stages of growth in rainbow trout (Oncorhynchus mykiss)

This study was conducted to determine the effect of growth hormone on some growth and immunity parameters at three stages of rainbow trout eyed egg, alvin and fry. The experiment was carried out in 4 treatments with concentrations of 0, 0.1, 0.5 and 1 mg/l of somatotropin hormone. For permeability, different experimental groups were treated with sodium hypochlorite (0.005 %) for 15 seconds before bathing with growth hormone; then they were immersed with different concentrations of growth hormone for 5 min. The specimens were then transferred to the tanks and were kept to 1.5 grams of weight. The results showed that the lowest feed conversion ratio (0.44) was observed at 0.1 mg concentration of were immersed with growth hormone in the egg stage, followed by in the alvine and then in the fry stage. The highest feed conversion ratio (0.59 ± 0.007) was observed in control group. The specific growth factor was the highest amount in the treatment of 0.1 egg stage (3.77 ± 0.77) and was significantly difference with control group (p <0.05). The lowest specific growth factor (3.33 ± 0.1) was observed in the control group. The highest lysozyme activity (0.0044 ± 0.055005) was observed in 0.1 and 0.5 concentrations in fish exposed to hormone in the egg stage, which was significantly higher than other experimental treatments (p <0.05). Also, the levels of immunoglobulin in fishes that were immersed with growth hormone in egg stage were significantly higher than other treatments (p <0.05). The results showed that growth hormone had a better performance in rainbow trout egg stage than the alvine and fry stage