Comparative evaluation of processed soybean meal (EnzoMealTM) vs. soybean meal as a fishmeal replacement in diets of rainbow trout (Oncorhynchus mykiss)

Authors: KUMAR, VIKAS - University Of Idaho; LEE, SEUNGHAN - University Of Idaho; Cleveland, Beth; ROMANO, NICHOLAS - University Of Arkansas At Pine Bluff; HARDY, RONALD - University Of Idaho; LALGUDI, RAMANATHAN - Ohio Soybean Council; MCGRAW, BARRY - Ohio Soybean Council

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2019
Publication Date: 2/1/2020
Citation: Kumar, V., Lee, S., Cleveland, B.M., Romano, N., Hardy, R., Lalgudi, R., Mcgraw, B. 2020. Comparative evaluation of processed soybean meal (EnzoMealTM) vs. soybean meal as a fishmeal replacement in diets of rainbow trout (Oncorhynchus mykiss). Aquaculture. 516:734652. https://doi.org/10.1016/j.aquaculture.2019.734652.
DOI: https://doi.org/10.1016/j.aquaculture.2019.734652

Interpretive Summary: The rapid global growth in fish farming has driven the aquafeed industry to seek alternative plant protein sources to reduce reliance upon fishmeal that originates from capture fisheries. Soybean meal (SBM) is the most commonly used plant protein in aquafeeds due to its high protein content, availability, and competitive price, however its nutritional value is limited by amino acid deficiencies and anti-nutritional factors. Industry partners developed a bioprocessing technology to improve the nutritional value of SBM and produced a product called Enzo meal with enhanced nutritional qualities. This study evaluated the effect of replacing fishmeal in rainbow trout diets with Enzo meal or SBM on growth performance, indices of nutrient utilization, and growth-related mechanisms. While fish consuming fish meal exhibited the best growth performance, the fish performance consuming Enzo meal was improved compared to fish consuming SMB. Consistent with this concept was better nutrient utilization in Enzo meal diets compared to SBM diets. These findings suggest that Enzo meal shows promise as an alternative to SBM in rainbow trout diets.

Technical Abstract: A 12-week feeding trial was conducted to compare low and high inclusions of conventional soybean meal (SBM) or enzyme-treated SBM (Enzo) as fishmeal replacements in the diets of rainbow trout, Oncorhynchus mykiss. Six isonitrogenous (43% crude protein) and isolipidic (19% crude lipid) diets were produced: a control diet (fishmeal-based) and five experimental diets replacing fishmeal protein by 8% or 16% with SBM (low or high SBM, respectively); 8% or 16% with Enzo (low or high Enzo, respectively); 16% with SBM + Enzo blended with 50:50 ratio (Enzo + SBM). Triplicate tanks, each containing 40 fish, were fed to apparent satiation. Compared with the control, all groups that consumed SBM or Enzo diets had lower growth performance and feed intake (P<0.05). However, fish fed Enzo showed significantly higher growth performance than those of fish fed SBM on each replacement level. Whole-body crude protein showed a decreasing trend with increasing dietary SBM and Enzo level, with significant differences detected between the control and the high SBM or high Enzo + SBM. However, fish fed control or low Enzo diets had no significant differences (P>0.05). Whole-body content of some essential amino acids (e.g. isoleucine, leucine and valine) showed a significant corresponding decrease with high dietary SBM inclusions. Trypsin activity decreased significantly with increasing dietary SBM and Enzo levels. Hepatic expression of GHR1 was greatest in high SBM and high Enzo + SBM treatments compared to the control diet, which exhibited the highest expression of IGF-II (P<0.05). Expression of IGFBP-1b1 was lowest in the control treatment and highest in the high SBM diet (P<0.05). Expression of myogenin and myoD, two myogenic proteins, was also affected by diet (P<0.05), with highest expression in the slowest growing treatment group (high SBM). The inferior performance of rainbow trout fed SBM compared to Enzo was likely due to reduced nutrient availability leading to alternations in the somatotrophic axis. Thus, Enzo shows promise as an alternative to SBM in rainbow trout diets.