Replacement of fish meal in sunshine bass diets with ethanol yeast

Ethanol yeast (EY), a co-product of bio-ethanol production, has potential to be a new fish meal (FM) alternative protein in aquafeeds. Two trials were conducted with sunshine bass to determine if EY could spare FM, and if FM replacement with EY affected stress tolerance. Sunshine bass fed diets containing a blend of EY and FM exhibited higher growth rates than fish fed FM or EY exclusively as the primary protein source. Low feed intake and increased FCR associated with the FM-free feed suggested that palatability may have been a barrier to complete replacement however a second trial evaluating the inclusion of a palatant/attractant to the EY-based formulations demonstrated little benefit of feed supplementation.  Dietary treatment had no significant effect on plasma cortisol or glucose in stressed fish. Our data suggest that optimal FM levels in EY based feeds are between 7.5% and 15%.  Although EY appears to be a suitable protein source for sunshine bass feeds and inclusion of this product in aquafeeds increases the sustainability of the aquaculture and biofuels industries, it cannot completely supplant FM as a critical constituent in feeds for this carnivorous taxon.