Considering the relation between the endocrine and immune systems, the effects of zeranol, a synthetic oestrogen compound, on the growth rate and nonspecific immune system in rainbow trout (Oncorhynchus mykiss, Walbaum) were investigated. For this reason, fish were fed a diet containing 0, 2.5, 5, 10 and 20 ppm zeranol for 21 days. When the data was statistically analysed, the body length in the fish groups fed with 5, 10 and 20 ppm, and the body weight for those given 10 and 20 ppm zeranol, were found to be significantly higher than in the control group. The specific growth rate and the condition factor results also supported the above results. In experiments related to nonspecific immunity, leucocyte fractions were analysed for phagocytic activity to yeast cells and for bactericidal activity by the measurement of the production of intracellular and extracellular superoxide radicals. It was determined that the phagocytosis and bactericidal activity of cells were significantly increased in conjunction with dietary zeranol doses, but no significant changes in serum total protein levels were observed. The results of the present study showed that in addition to its anabolic effect, zeranol stimulated nonspecific immune responses in rainbow trout.

Considering the relation between the endocrine and immune systems, the effects of zeranol, a synthetic oestrogen compound, on the growth rate and nonspecific immune system in rainbow trout (Oncorhynchus mykiss, Walbaum) were investigated. For this reason, fish were fed a diet containing 0, 2.5, 5, 10 and 20 ppm zeranol for 21 days. When the data was statistically analysed, the body length in the fish groups fed with 5, 10 and 20 ppm, and the body weight for those given 10 and 20 ppm zeranol, were found to be significantly higher than in the control group. The specific growth rate and the condition factor results also supported the above results. In experiments related to nonspecific immunity, leucocyte fractions were analysed for phagocytic activity to yeast cells and for bactericidal activity by the measurement of the production of intracellular and extracellular superoxide radicals. It was determined that the phagocytosis and bactericidal activity of cells were significantly increased in conjunction with dietary zeranol doses, but no significant changes in serum total protein levels were observed. The results of the present study showed that in addition to its anabolic effect, zeranol stimulated nonspecific immune responses in rainbow trout.