Assessing the nutritional value of an enzymatically processed soybean meal in early juvenile red drum, Sciaenops ocellatus L

Abstract

We assessed the nutritional value of an enzymatically processed soybean meal (HP300, Hamlet Protein Inc., Findlay, Ohio, USA; hereafter ESBM) in the diet of red drum, Sciaenops ocellatus. A digestibility and two growth trials (Trials I and II) were conducted to: i) assess the in vivo digestibility of ESBM and commodity soybean meal (SBM); ii) assess the maximum replacement of the digestible protein (DP) from fishmeal (FM) with ESBM (MAX REPLESBM); iii) validate the estimated MAX REPLESBM and compare it against SBM. All experimental diets were formulated to contain 32% DP, 12% lipid, and an estimated 13.8kJg−1 digestible energy. Seven experimental diets were designed in Trial I: a FM reference diet (FM-100), designed to contain all its protein from Special Select menhaden FM; and six test diets designed to replace the DP from FM in the FM-100 diet on a isonitrogenous basis, at 15% incremental levels (ESBM-15 to ESBM-90). Each diet was fed to juvenile red drum (5.72g) in duplicate aquaria connected as a closed recirculating system. After 6weeks of feeding, responses of red drum fed the various diets differed considerably, with survival ranging from 78 to 95%, final weight from 24.5 to 40.0g, weight gain (% of initial) from 330 to 597%, and feed efficiency (FE) from 0.7 to 1.0. Second order polynomial regression analysis of weight gain and FE data indicated a MAX REPLESBM of 72 and 63%, respectively. After feeding the FM-100, ESBM-70, and a SBM-70 diets to juvenile red drum (1.7g) in Trial II (8weeks, n=3), no differences in production performance of fish were found among treatments. These results indicated that either ESBM or SBM can replace up to 70% of FM DP in the diet of early juvenile red drum without detrimental effects on production performance. Statement of relevanceThe currently study represents an addition to the increasing number of studies evaluating alternative protein sources in the diet of carnivorous fish species. We used red drum as a model and demonstrated the applicability of soybean products as partial substitutes for dietary fishmeal. Once replicated under commercial production settings, our results will contribute for a more sustainable aquaculture industry.