Growth Performance and Body Composition of Palmetto Bass Fed Five Levels of Dietary Protein at Two Energy-to-Protein Ratios

Abstract

A feeding trial was conducted to determine the effects of dietary crude protein (CP) level and digestible energy-to-protein (DE:P) ratio on the growth performance and body composition of palmetto bass (female striped bass Morone saxatilis × male white bass M. chrysops). Ten soybean-meal-based diets were prepared to contain 30, 35, 40, 45, or 50% CP at DE:P ratios of 33.48 or 41.85 kJ/g CP. The diets contained lyophilized palmetto bass muscle as the sole animal protein source to improve dietary amino acid composition. Wheat middlings and corn grain were the major sources of carbohydrates, and the diets were formulated to meet the known nutritional requirements of palmetto bass. Fish fed 35% or 40% CP at 33.48 or 41.85 kJ/g CP had significantly (P ≤ 0.05) greater weight gains and higher feed efficiency ratios than fish fed the other diets. The protein efficiency ratio (g weight gain/g CP consumed) decreased and visceral fat ([g visceral fat × 100]/g body weight) increased as the dietary protein level increased in both DE:P treatments. The hepatosomatic index ([g liver weight × 100]/g body weight) increased with the dietary protein level up to 40–45% CP. Whole-body muscle content and fillet yield did not differ significantly among fish fed any of the diets at either DE:P ratio. The lipid content of fillets was higher among fish fed 45–50% CP than among those fed up to 40% CP. Hematocrit and serum protein concentrations were not affected by the dietary CP level or the DE:P treatment. Overall, the DE:P ratio had little or no effect on most of the parameters of interest. Based on our comparisons of weight gain, diet utilization efficiency, and body composition among treatment groups, a 35% CP diet with 41.85 kJ/g CP was considered optimum for palmetto bass under the conditions of this study.