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.