Abstract
Efforts to reduce the use of fishmeal in aquafeeds for carnivorous marine fish have been a focal point of aquaculture nutrition research in recent years. Building upon such research, this study was designed to compare the digestibility, growth and performance of three soy protein products as potential replacements for fishmeal in feeds for Florida pompano, Trachinotus carolinus. Two soy protein concentrates (Solae SPC™ Profine® and Selecta SPC™) and a fermented soy protein product (Hamlet protein™) were initially tested for digestibility of crude protein, crude energy and 17 amino acids in adult Florida pompano (average weight 577g) using the indirect method of fecal collection. In the second experiment, growth and performance of diets formulated with these ingredients were evaluated in juveniles (average initial weight 27.8g) and sub-adults (average initial weight of 127.7g). The two soy protein concentrates demonstrated a significantly higher apparent digestibility of energy than the fermented soy protein (p=0.00). Solae SPC yielded the highest apparent digestibility of crude protein (p= 0.001). No significant differences were found in the digestibility of important indispensable amino acids arginine and methionine. However, Selecta SPC and Solae SPC yielded the highest digestibility of the remaining essential amino acids. In the juvenile growth experiment, performance metrics of average daily growth and gross protein intake were significantly greater in the fish fed the Solae SPC diet (p= 0.02). The feed conversion ratio (FCR) and fish in fish out (FIFO) ratio, commonly used in evaluating economic and environmental feed efficiency, were significantly lowest for the Solae SPC diet (p=0.049). In a third experiment on sub-adult pompano (127.7g average weight at stocking), a repeat of the growth experiment was conducted. Undetermined factor(s) in the manufacturing of three of the four diets led to severely reduced palatability, yielding poor performance and unreliable data through all metrics. While a comparison of the soy protein products was undermined, a commercial diet and a control diet had similar and healthy consumption rates and could be compared. While these diets were neither iso-proteic nor iso-lipidic, a comparison of their performance metrics yielded interesting results. Across almost all growth and performance metrics in sub-adult Florida pompano, the control diet (with 13.1% soybean meal), performed equally or better than the more expensive commercial diet, supporting the increasingly common notion that the diets should be both species and size-specific, as nutritional requirements appear to change throughout life. These preliminary results also corroborated the main hypothesis of this study, that a Florida pompano diet whose protein is supplemented with soybean meal is not only viable but economically and environmentally preferable to a fishmeal rich, high-protein diet.