Growth efficiency, survival and haematological changes in great sturgeon (Huso huso Linnaeus, 1758) juveniles fed diets supplemented with different levels of thymol-carvacrol

This study was conducted to evaluate the effects of dietary thymol-carvacrol on the growth performance and blood parameters in great sturgeon. A basal diet was formulated using common feed ingredients supplemented with thymol-carvacrol powder at 0, 1, 2, and 3 g kg−1, leading to four experimental diets. Each experimental diet was randomly assigned to triplicate 350 L tanks. Great sturgeon with an initial weight of 43.6 ± 1.6 g was randomly distributed in the experimental tanks. Results showed that inclusion of dietary thymol-carvacrol significantly increased the final weight, specific growth rate (SGR) and weight gain (P<0.05) of great sturgeon compared to the control. Feed conversion ratio (FCR) was also improved (P<0.05) in fish that received thymol-carvacrol, but it had no effect on survival (P>0.05). The total number of red and white blood cells was not different among the treatments but fish feeding on thymol-carvacrol diets had more lymphocytes (P<0.05). In conclusion, administration of thymol-carvacrol can improve growth performance and immunity of great sturgeon.