THE POTENTIAL EFFECTS OF COMMERCIAL FEEDING PROTOCOL ON PROTEASE ACTIVITIES AND CORTISOL STRESS RESPONSES OF MEAGRE (ARGYROSOMUS REGIUS)

The present study is designed to report the potential effects of commercial feeding protocol on protease activities and cortisol stress responses of meagre (Argyrosomus regius) from fertilized eggs to 45 days after hatching (DAH). The inhibition effects of six commercial diets (Gemma Micro 150 (100-200μ), Caviar (200-300μ), Caviar (300-500μ), Perla Larva Proactive 4.0 (300-500μ), Perla MP-S(700 μ) and Perla Plus 3.0(400-800 μ)) and protease contributions of live foods (enriched rotifer, Artemia nauplii and Artemia metanauplii) were tested in the study. Samples of meagre were collected from fertilized eggs to 45 DAH. All analyses were carried out in triplicates.The differences observed in the total length and weight values were statistically significant (p< 0.05). The lowest and highest total length values were 3.06±0.23 mm (3 DAH) mm and 33.28±0.68 mm (45 DAH), respectively. The lowest and highest weight values were 0.53±0.01 mg (3 DAH) and 467.67±1.47 mg (45 DAH), respectively. The differences in protease activities of meagre larvae were statistically significant (p< 0.05). The highest and lowest protease activities of meagre larvae were 477.13±39.30 U/mg protein (3 DAH) and 10.05±1.16 U/mg protein (20 DAH), respectively. The digestive proteases of meagre larvae showed the greatest sensitivity to protease inhibitors present in Gemma Micro 150 (100-200μ). Fertilized eggs of meagre had low cortisol level (0.68 ng/g). Cortisol values increased rapidly up to hatching (2.43±0.06 ng/g) and followed by a decrease in prelarval stage (1.80±0.01 ng/g) and then remained relatively until before mouth opening (1.76±0.03 ng/g). From 3 to 45 DAH, the highest and lowest cortisol values of meagre larvae were 6.13±0.18 ng/g (15 DAH) and 1.98±0.17 ng/g (30 DAH) respectively. In conclusion, the presence of cortisol in fertilized eggs of Argyrosomus regius confirms that they are maternal origin. Perla MP-S(700 μ) and Perla Plus 3.0(400-800 μ)) are suggested due to good performances from 3 to 45 DAH but not Gemma Micro 150 (100-200μ). Caviar (200-300μ) and Caviar (300-500μ) are the moderately advisable as commercial diets in the feeding protocol of meagre larvae except for more inhibitions than 50%.