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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #310642
Title: Effects of a phytogenic feed additive on susceptibility of channel catfish to Edwardsiella ictaluri and levels of mannose binding lectin

Author
item Peterson, Brian
item PEATMAN, ERIC - Auburn University
item OURTH, DON - University Of Memphis
item Waldbieser, Geoffrey - Geoff

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2015
Publication Date: 4/1/2015
Citation: Peterson, B.C., Peatman, E., Ourth, D.D., Waldbieser, G.C. 2015. Effects of a phytogenic feed additive on susceptibility of channel catfish to Edwardsiella ictaluri and levels of mannose binding lectin. Fish and Shellfish Immunology. 44:21-25.

Interpretive Summary: A study was conducted to investigate the effect of essential oils (Digestarom® P.E.P. MGE) on growth performance and disease susceptibility to Edwardsiella ictaluri. Two hundred and fifty juvenile channel catfish were allotted into the following treatments: Control (floating diet, Fishbelt Feeds, Inc.) and EO (floating diet supplemented with essential oils). The fish were fed their respective diets for 6 weeks. At the end of the study, all fish were exposed to virulent E. ictaluri by bath immersion. Plasma and tissue samples were taken to quantify protein and gene expression levels of mannose binding lectin (MBL). MBL has been shown to be an important player in the immune response to microbial infections. Weight gain and food conversion ratio were similar between treatments. After exposing fish to virulent E. ictaluri for 21 days, survival was higher (69.5 vs 48.4%) in fish fed EO compared to controls. One day after challenge, plasma MBL levels were down-regulated in the control fish compared to non-challenged fish. In the EO fish, MBL levels were similar to non-challenged fish but significantly higher than control fed fish. By day 7, plasma MBL levels increased in control fed fish to levels observed in the EO and non-challenged fish. Gene expression levels of MBL were similar between treatments except on day 14, MBL mRNA levels were upregulated 15-fold in fish fed EO compared to control fed fish and non-challenged fish. The results demonstrate that essential oils improved survival of channel catfish challenged with E. ictaluri. Mechanisms through which essential oils improve survival may involve MBL.

Technical Abstract: A study was conducted to investigate the effect of a phytogenic feed additive (Digestarom® P.E.P. MGE) on growth performance and disease susceptibility to Edwardsiella ictaluri. Two hundred and fifty juvenile channel catfish (7.2 ± 0.1 g) were allotted into the following treatments: Control (floating diet, Fishbelt Feeds, Inc.) and EO (floating diet supplemented with essential oils; Digestarom® P.E.P. MGE at 200 g/ton). The fish were fed their respective diets for 6 weeks. At the end of the study, all fish were exposed to virulent E. ictaluri by bath immersion. Plasma and tissue samples were taken to quantify protein and gene expression levels of mannose binding lectin (MBL). Weight gain and food conversion ratio were similar between treatments. After exposing fish to virulent E. ictaluri for 21 days, survival was higher (69.5 vs 48.4%) in fish fed EO compared to controls (P < 0.05). One day after challenge, plasma MBL levels were down-regulated in the control fish compared to non-challenged fish. In the EO fish, MBL levels were similar to non-challenged fish but significantly higher than control fed fish (P < 0.001). By d 7, plasma MBL levels increased in control fed fish to levels observed in the EO and non-challenged fish. Gene expression levels of MBL were similar between treatments except on d 14, MBL mRNA levels were upregulated 15-fold in fish fed EO compared to control fed fish and non-challenged fish (P < 0.001). The results demonstrate that essential oils improved survival of channel catfish challenged with E. ictaluri. Mechanisms through which essential oils improve survival may involve MBL.