Production Performance and Stress Tolerance of Sunshine Bass Raised on Reduced Fish Meal Feeds Containing Ethanol Yeast

Abstract

Ethanol yeast (EY) has been shown to be an effective alternative to fish meal (FM) in diets of sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis). Diets containing blends of FM and EY yield production performance similar or superior to that of diets containing no EY. Complete replacement of FM with EY, however, reduces feed palatability, impairs production performance, and may affect other aspects of livestock vigor. Accordingly, the objectives of this study were to determine the effects of dietary EY inclusion (with or without a palatant) on the feed intake, growth performance, and physiological robustness of sunshine bass after stressor exposure. Formulations were developed containing 15, 7.5, and 0% FM with EY as the primary alternative protein source. Experimental diets were prepared according to these formulations with and without the addition of 1% soluble canola protein concentrate as a palatant. Replicate tanks of juvenile sunshine bass (∼4.4 g) were fed the experimental feeds twice daily to apparent satiation for 9 weeks. Production performance was assessed, and then the fish were subjected to a 2-min net-chasing stress challenge protocol. Tissue samples were collected to allow for the determination of organosomatic indices and pre- and postchallenge hematology. Complete replacement of FM with EY resulted in reduced growth performance and efficiency and significantly altered whole-body proximate composition, reducing carcass protein and increasing carcass lipid. Palatant inclusion had no effect on diet acceptance or production performance. Plasma glucose and lysozyme activity were significantly affected by stress; however, dietary treatment did not affect these parameters. While cortisol levels were marginally higher among stressed fish, they were higher than expected in unstressed fish. Our results confirm previous research suggesting that the optimal level of FM in EY-based sunshine bass feed is between 7.5% and 15%. Further research is needed to fully understand the utilization of these feeds and their effects on the physiological status of sunshine bass.

Received July 13, 2010; accepted October 1, 2010

ACKNOWLEDGMENTS

We thank Andy Yung, Bonnie Mulligan, Heidi Lewis, and Patrick Blaufuss for assistance with feeding trial and data collection. We thank Rebecca Atkinson for assistance with protein analysis. We also thank Archer Daniels Midland Co., Stephanie Block, and Mike Cecava for providing technical support and supplying the ethanol yeast used in this study. We thank Omega Protein (Houston, Texas) for the donation of fish meal and fish oil used in preparing our experimental feeds. This study was funded in part by a grant from the Illinois–Indiana Sea Grant 2006–02560-07.