Assessment of dietary yeast-based additives for cultured catfish and tilapia health

Authors: CACOT, GUILLAUME - Auburn University; DAVIS, ALLEN - Auburn University; Lafrentz, Benjamin; LILES, MARK - Auburn University; BUTTS, IAN - Auburn University; Shoemaker, Craig; Beck, Benjamin; FARMER, MARK - Diamond V Mills, Inc; BRUCE, TIMOTHY - Auburn University

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Identification of alternatives to antibiotics for treatment of disease is critical for the sustainability of aquaculture. In this research, the use of a commercial fermented yeast product (postbiotic) was tested for an ability to enhance growth of catfish and tilapia and to stimulate the immune response for an enhanced ability to fight disease. Catfish and tilapia were fed a control diet and two experimental diets containing different levels of the fermented yeast product for approximately two months. After the feeding trial, fish were sampled for growth metrics and metrics of the immune system. There were no differences in the growth metrics of both fish species at the end of the feeding trial, and a few of the immune function metrics did differ among the treatment groups. Catfish and tilapia were experimentally infected with bacterial pathogens following the feeding period to evaluate survival. There were no differences among the catfish treatment groups; however, tilapia fed the fermented yeast product did exhibit increased survival. These results suggest that this postbiotic may be beneficial in protecting Nile tilapia against Streptococcus iniae infection by influencing immune parameters and additional research is needed to evaluate the potential of this postbiotic for improving catfish health and disease control.

Technical Abstract: Channel catfish (Ictalurus punctatus) and Nile tilapia (Oreochromis niloticus) are two aquaculture species of great importance. Intensive production is often hindered by poor growth performance and disease mortality. The aim of this study was to evaluate the potential of a commercial fermented yeast product, DVAQUA, on channel catfish and Nile tilapia growth performance metrics and disease resistance. Channel catfish and Nile tilapia were fed practical diets supplemented with 0, 1, or 4 g kg-1 of DVAQUA over an approximate 2 months feeding periods in recirculation aquaculture systems. To assess the potential of the postbiotic against common aquaculture pathogens, juvenile catfish were subsequently challenged by immersion with Edwardsiella ictaluri S97-773 or virulent Aeromonas hydrophila ML09-119. Nile tilapia juveniles were challenged by injection- with Streptococcus iniae ARS-98-60. Serum lysozyme activity, blood chemistry, and growth metrics were measured at the end of the feeding period, but no differences were observed across the different metrics, except for survival. For the pathogen challenges, there were no differences in endpoint mortality for channel catfish with either pathogen (P>0.05). In contrast, Nile tilapia survivability to S. iniae infection increased proportionally to the inclusion of DVAQUA (P=0.005). Changes to sera lysozyme activity were also noted in the tilapia trial, with a reduction of activity in the fish fed 4 g kg-1 of DVAQUA compared to the control diet (P=0.031). Expression profiles of proinflammatory genes and antibodies were also found to be modulated in channel catfish fed the postbiotic, indicating some degree of protective response. These results suggest that this postbiotic may be beneficial in protecting Nile tilapia against S. iniae infection by influencing immune parameters and additional research is needed to evaluate the potential of this postbiotic for improving catfish health and disease control.