Humic substance combined with butyric acid could promote resistance to bacteria co-infections in channel catfish production

Authors: OLADIPUPO, ABDULMALIK - Auburn University; KELLY, ANITA - Auburn University; Lafrentz, Benjamin; ROY, LUKE - Auburn State University; DAVIS, D. - Auburn State University; BRUCE, TIMOTHY - Auburn University

Submitted to: Fish Farming News
Publication Type: Popular Publication
Publication Acceptance Date: 11/25/2024
Publication Date: 12/4/2024
Citation: Oladipupo, A.A., Kelly, A.M., Lafrentz, B.R., Roy, L.A., Davis, D.A., Bruce, T.J. 2024. Humic substance combined with butyric acid could promote resistance to bacteria co-infections in channel catfish production. Fish Farming News 2024 2024(2):16-17. 2024

Interpretive Summary: No Interpretive Summary

Technical Abstract: Interactions between two or more bacteria can drive diseases, increase mortality in catfish ponds, and complicate treatments. The most frequently reported bacterial diseases in catfish production ponds are caused by Flavobacterium covae (columnaris disease), virulent Aeromonas hydrophila (vAh), or Edwardsiella ictaluri (enteric septicemia of catfish (ESC) or hole-in-the-head disease). In catfish ponds, these bacteria can remain and work together, causing higher mortality rates, and antibiotic treatment does not always have effects against these coordinated infections. Therefore, producers need a cost-effective and sustainable alternative to effectively manage these occurrences and maintain catfish production in the United States. Previously, including a humic substance (HS), a natural, environmentally friendly compound, in catfish diets improved the survival of fish cultured in commercial pond water. These findings established that HS stimulated the immune system of catfish, allowing them to fight off bacterial infections. To evaluate this further on fish with more than one bacterial infection, a humic and butyric acid blend (IFC4) or yeast cell wall (YCW) was included in a practical diet of channel catfish fingerlings as a single or combined (IFC4+YCW) supplement compared with a diet without any supplement (Basal). Channel catfish were fed with these respective diets for 45 days, after which they were placed into smaller aquaria. Then dosages of bacteria were introduced for 1 hour with a single infection of columnaris or ESC or co-infection with simultaneous additions of columnaris and ESC. After the feeding trial, the result showed that catfish fed a diet supplemented with IFC4 had improved lysozyme activity, a natural immunity indicator, in the blood, while fish offered the IFC4+YCW had a similar increase in body skin mucus. Fourteen days after exposure to the bacteria, no mortality was observed in the columnaris-infected group; the cumulative mortality of fish infected with just ESC was IFC4 (22%), YCW (30%), IFC4+YCW (38%), and Basal (48%). While the single columnaris group did not induce any mortality, overall mortality increased in the co-infected group (IFC4 (28%), YCW (55%), IFC4+YCW (70%), and Basal (70%)). Meanwhile, the lowest mortality occurred in the IFC4-fed catfish in both single ESC and co-infected cases. This study clearly shows that co-infection could significantly impact mortality in catfish-rearing systems. While a single bacterial infection is often targeted for treatment, severe disease outbreaks could occur in commercial catfish ponds due to co-infection from multiple bacteria. Moreover, using humic substances blended with butyric acid as a feed supplement could be a management tool to improve catfish’s natural immunity against multiple infections.