Evaluation of the ability of Pichia guilliermondii to improve growth performance and disease resistance in rainbow trout (Oncorhynchus mykiss)

Authors: Sealey, Wendy; CONLEY, ZACHARIAH - Us Fish And Wildlife Service; HINMAN, BRETT - Us Fish And Wildlife Service; O'NEILL, THOMAS - Us Fish And Wildlife Service; BOWZER, JOHN - Adm Animal Nutrition; BLOCK, STEPHANIE - Adm Animal Nutrition

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2021
Publication Date: 1/18/2022
Citation: Sealey, W.M., Conley, Z.B., Hinman, B.T., O'Neill, T.J., Bowzer, J., Block, S. 2022. Evaluation of the ability of Pichia guilliermondii to improve growth performance and disease resistance in rainbow trout (Oncorhynchus mykiss). Journal of the World Aquaculture Society. 53(2):411-423. https://doi.org/10.1111/jwas.12872.
DOI: https://doi.org/10.1111/jwas.12872

Interpretive Summary: Feed additives are included in animal feeds to better utilize raw materials and reduce feed costs by improving animal growth and health. Natural products, like yeast, are often added to fish feeds for this purpose. However, the benefit of yeast supplementation to fish feeds is affected by both the type of yeast and the level of inclusion. USDA ARS physiologist Wendy Sealey and colleagues at the Bozeman Fish Technology Center recently tested the effects of a novel yeast product containing Pichia guilliermondii on rainbow trout growth and mortality following disease exposure. In two separate feeding trials, fish were fed rainbow trout feeds supplemented with 0.3 or 0.6% of a commercial source of P. guilliermondii alone or 0.3% P. guilliermondii in combination with a commercial dietary gut supplement at 0.1%. Dietary supplementation of either P. guilliermondii or the gut supplement improved growth efficiency in rainbow trout when fed for 16-weeks but had no effect on mortality following disease exposure. These results suggest the potential application of these products for improving rainbow trout growth. Defining the ability of novel yeast products to improve growth efficiency and health of rainbow trout can help rainbow trout producers and feed manufactures make informed decisions regarding the value of including such products in their fish feeds.

Technical Abstract: The supplementation of aquaculture diets with yeast and yeast-derived products has been investigated at length as a means of improving growth and disease resistance in aquatic species. The resultant inconsistent effects reported are purportedly due to differences in the fish and yeast species examined, and the levels of dietary supplementation employed. This study examined the effects of supplementing a novel yeast product containing Pichia guilliermondii on juvenile rainbow trout, Oncorhynchus mykiss, growth, and disease resistance. In two separate feeding trials, fish (initial weight 6.2 and 10.6 g, respectively), were fed an extruded diet (41% digestible protein and 18% crude lipid) supplemented with 0.3 or 0.6% of a commercial source of P. guilliermondii alone or 0.3% P. guilliermondii with a commercial dietary gut supplement at 0.1%. Prior to the end of each feeding trial, a subsample of fish from each tank were exposed by immersion with enteric red mouth, Yersinia ruckeri (trial 1) or injection with coldwater disease, Flavobacterium pyschrophilum (trial 2). Mortality was monitored for 21 d following pathogen exposure. No significant effect of P. guilliermondii supplementation on mortality was observed. At the conclusion of the feeding trials, dietary supplementation of either P. guilliermondii or the gut supplement improved growth and food conversion efficiency in rainbow trout when fed for 16-weeks (trial 2) but not when fish were fed for 7-weeks (trial 1), or when both supplements were used in combination. These results suggest the potential application of these products as functional additives for trout feeds; however, additional investigation regarding the efficacy of whole-cell and disrupted wall components of P. guilliermondii is needed to better assess their potential effects on rainbow trout immune responses.