In vitro effects of butyrate and propionate supplementation and high-plant-protein diets on performance, innate immune responses, and intestinal microbiota of red drum (Sciaenops ocellatus)

Authors: YAMAMOTO, FERNANDO - Texas A&M University; OLDER, CAITLIN - Texas A&M University; Hume, Michael; HOFFMANN, ALINE - Texas A&M University; GATLIN III, DELBERT - Texas A&M University

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: The objective of this study was to investigate effects of sodium butyrate and sodium propionate individually and in combination on the production of fish-eating, farmed red drum fish fed a diet containing high levels of plant protein. A synergistic effect was seen on the inhibition of two fish bacterial pathogens when butyrate and propionate were added together in growth cultures. A molecular technique showed that the composition of fish intestinal microbial communities in growth cultures were changed slightly by the butyrate and propionate when compared to the control culture containing no organic acids. When compared to fish given control feed containing no organic acids, propionate in feed slightly impaired fish growth, while butyrate slightly impaired protein digestion. Butyrate in feed reduced the level of stress molecules in the blood when compared to fish fed the control diet. Butyrate also supported an increase in the numbers of beneficial bacteria genetic sequences and the production of vitamin B12. However, butyrate in combination with propionate increased the numbers of bacteria associated with improper intestinal functioning. Results showed positive effects on digestive bacterial populations and stress, while showing some negative effects on intestinal function. Further studies are needed to optimize the use of these organic acids to improve health and growth of red drum fed high levels of plant protein. These results are of interest to researchers and producers seeking alternatives to antibiotics to improve food utilization, health, and production.

Technical Abstract: The objective of this study was to investigate possible effects of supplementing sodium butyrate and sodium propionate individually and in combination in a diet formulated with high-plant-protein inclusion for the carnivorous red drum. The inhibitory property of these organic acids (OA) was first tested in vitro against two common fish pathogenic bacteria Aeromonas hydrophyla and Streptococcus agalactiae. A synergistic effect was observed for the minimum inhibitory concentrations against both bacteria when butyrate and propionate were added together in the media. Additionally, red drum intestinal microbiota were incubated under in vitro anaerobic conditions with feed-broth media preparations containing the OA individually and in combination. The microbial communities proved to be mildly affected in vitro by the OA, with the butyrate and propionate treatments having 90% similarity with the basal diet when analyzed by denaturing gradient gel electrophoresis. A higher relative abundance of the order Clostridiales and class Clostridia was observed for the control samples after DNA sequencing. For the in vivo comparative feeding trial, a high-plant-protein diet was formulated as the control, and the organic acids were supplemented at either 0 or 5 g/kg of butyrate, propionate, or their combination. Five tanks containing 18 juvenile red drum initially weighing ~4.5 g/fish were fed each diet for 8 weeks after which production performance, whole-body proximate composition, whole-blood and plasma immunological responses, and intestinal microbial community profiles were evaluated. Fish fed diets containing propionate had slightly impaired growth performance, and red drum fed diets with butyrate presented slightly impaired protein conversion efficiency while dietary butyrate reduced the production of reactive oxygen species in whole blood compared to fish fed the control diet. Supplementation of organic acids in the diet modulated intestinal microbiota. Butyrate appeared to confer a beneficial effect on red drum, as the relative abundance of Cetobacterium spp. was higher. The predicted metabolic functions of the intestinal microbiome using PICRUSt2 were most affected by dietary butyrate, which resulted in communities predicted to have enrichment of cobalamin biosynthesis related pathway. On the other hand, supplementation of butyrate with propionate resulted in a higher relative abundance of bacterial taxa associated with intestinal dysbiosis.