The effect of dietary supplementation of L-carnitine on resistance to temperature and salinity stresses in Sobaity seabream Sparidentex hasta

To investigate the effect of dietary supplementation of L-carnitine on resistance to temperature and salinity stresses in Sobaity fry، an experiment was carried out with 240 pieces of fish with average initial weight of 3. 01±0. 03 g for 10 weeks. Experimental treatments were consisted of four levels of 0، 500، 1000 and 1800 (respectively control، LC500، LC1000 and LC1800) mg L-Carnitine per kg of diet، each with three replicates in a completely randomized design. During the experimental period، feeding was performed by hand and the fish were daily fed to satiation at three intervals. At the end of the experimental period، fish were exposed to two temperatures of 15 and 37°C for 30 minutes for thermal stress test and to two salinity levels of 12 and 70 ppt for one hour for salinity stress test. The results showed that in LC1000 and LC1800 treatments، the resistance to high temperature، low temperature and high salinity stresses increased significantly compared to control group (P<0. 05). Furthermore، there was no significant difference in resistance to low salinity stress between the treatments (P>0. 05). The results of present research revealed that the dietary supplementation of L-carnitine could favorably affect the resistance to temperature and salinity stresses in Sobaity fry. Between the different levels of L-carnitine used، the most effective dose on resistance to temperature and salinity stresses in Sobaity seabream fry was the level of 1000 mg L-carnitine per kg of diet.