Potential for a Mycotoxin Deactivator to Improve Growth and Performance of Rainbow Trout fed High Levels of an Ethanol Industry Co‐Product, Grain Distiller's Dried Yeast

Abstract

Coproducts from the production of fuel ethanol may have the potential to be used as protein sources for Rainbow Trout Oncorhynchus mykiss if dietary supplementation strategies that can maintain fish performance can be identified. A random sample of one such coproduct, grain distiller's dried yeast (GDDY), contained detectable levels of ochratoxin A, deoxynivalenol, zearalenone, fumonsin B1, and fumonsin B3. Therefore, the goal of this study was to test whether growth performance of Rainbow Trout fed GDDY could be improved by dietary supplementation of a mycotoxin deactivator (Mycofix Plus). The study was conducted as a 2 × 3 factorial design in which there were two levels of mycotoxin deactivator (0.1% or 0%) and three levels of GDDY inclusion (0, 15, and 30%). All diets were formulated to include 42% digestible protein and 20% crude lipid and were balanced for lysine, methionine, threonine, and total phosphorus. Juvenile Rainbow Trout (average initial body weight, 26.4 ± 0.9 g [mean ± SD]) were stocked at 15 fish per tank, three replicates per diet, and were fed twice daily for 12 weeks. Grain distiller's dried yeast inclusion at 15% and 30% of the diet reduced the growth of Rainbow Trout (P = 0.0010). In contrast, no significant differences in feed intake and feed conversion ratio (FCR) were observed for Rainbow Trout fed diets having the 0% and 15% GDDY inclusion levels. However, increased feed intake (P = 0.0002) and FCR (P = 0.0002) were observed in Rainbow Trout fed the 30% GDDY diet. Only minor trends of increased fish growth (P = 0.0773) and protein (P = 0.0527) and energy (P = 0.0538) retention were observed when mycotoxin deactivator was supplemented regardless of yeast inclusion. These results suggest that there are minor benefits of myctoxin deactivator supplementation to Rainbow Trout diets where mycotoxin contamination may be suspected but was independent of GDDY inclusion level.

Refining Inclusion Levels of Grain Distiller's Dried Yeast in Commercial‐type and Plant‐based Diets for Juvenile Rainbow Trout, Oncorhynchus mykiss

“…FCRs for both feeding trials showed no significant effect of increased FCR with increased GDDY inclusion level ( P = 0.358 and 0.064, respectively). These data support recommended inclusion levels that are in general agreement but higher than those of Hauptman et al (, ). Hauptman et al () examined the effects of eight different GDDY inclusion levels from 0 to 30% and found that levels higher than 11.2% lead to a linear decrease in performance and increased FCR when fish meal protein was replaced with GDDY.…”

“…The reasons for the success of higher inclusion levels in this study as compared to Hauptman et al (, ) likely stem from the replacement strategy used in the current study. In this study, the effect of GDDY inclusion was evaluated independent of any possible confounding effects of decreasing fish meal levels.…”

“…Hauptman et al () examined the effects of eight different GDDY inclusion levels from 0 to 30% and found that levels higher than 11.2% lead to a linear decrease in performance and increased FCR when fish meal protein was replaced with GDDY. In a subsequent study, Hauptman et al () examined inclusion levels of 0, 15, and 30% and found that GDDY at 15 and 30% of the diet reduced growth but FCR was only negatively increased at 30% GDDY inclusion. Using a similar fish meal replacement approach, Gause and Trushenski (, ) recommended dietary GDDY inclusion levels of 27.0–41.3% for hybrid striped bass.…”

“…Gause and Trushenski (, ) explored the potential of GDDY as a fish meal replacement in diets for sunshine bass and found that GDDY can replace up to 75% of the protein provided by fish meal without having a negative effect on growth rate and FCR. Similarly, studies with rainbow trout, O. mykiss , demonstrated that GDDY could effectively replace up to approximately 40% of dietary fish meal protein (Hauptman et al , ). Hauptman et al () also demonstrated that the protein digestibility of GDDY was higher than the average fish meals analyzed by Gaylord et al (, ), and was comparable to the plant concentrate ingredients soy protein concentrate (99%) and corn protein concentrate.…”

“…Grain distiller's dried yeast (GDDY), the yeast fraction suspended in the supernatant and separated from distiller's dried grains when manufacturing ethanol from corn, has been investigated as a partial replacement ingredient for the protein and amino acids from fish meals (Gause and Trushenski , ; Hauptman et al , ). Gause and Trushenski (, ) explored the potential of GDDY as a fish meal replacement in diets for sunshine bass and found that GDDY can replace up to 75% of the protein provided by fish meal without having a negative effect on growth rate and FCR.…”