The effect of different dietary protein levels on growth performance and nutrient utilization of snarpsnout sea bream (Diplodus puntazzo)

摘要

Abstract This study evaluated the effects of different dietary protein levels on growth performance and nutrient utilization of snarpsnout sea bream (Diplodus puntazzo) juveniles. Five isoenergetic diets were formulated to contain a dietary protein level at 30 (P30), 35 (P35), 40 (P40), 45 (P45) and 50 (P50). Each diet was randomly assigned to triplicate groups of fish (IBW 2.80 g) and fed to apparent satiation for 100 days. The dietary protein to energy ratio significantly affected the feed intake with the lower ratios leading to a higher feed consumption. The growth performance of D. puntazzo was gradually increased as the dietary protein level increased up to 40 and then gradually reduced as the dietary protein increased further to 45 and 50. The feed efficiency got improved as dietary protein levels increased up to 45 but slightly decreased at 50 protein level. A second‐degree polynomial regression analysis estimated that a dietary protein level at 41.4 and 43.8 delivered the maximum weight gain and the higher feed efficiency, respectively. The increased dietary carbohydrate and lipid levels in fish fed a low protein diet (P30) resulted in a significant deterioration of feed conversion and growth rates showing also reduced nutrient retentions and causing severe mortalities.