Aquaculture America 2020

February 9 - 12, 2020

Honolulu, Hawaii

IN VITRO AND IN VIVO EFFECTS OF BUTYRATE, PROPIONATE, AND THEIR COMBINATION IN HIGH-PLANT-PROTEIN-DIETS FOR RED DRUM Sciaenops ocellatus

Fernando Y. Yamamoto*, Michael Hume, Delbert M. Gatlin III
 
 *Department of Wildlife and Fisheries Sciences; Texas A&M University System,
 534 John Kimbrough Blvd 77843-2258 , College Station, TX, USA
 

Disease outbreaks are recognized as a major bottleneck for aquaculture production and trade. It is estimated that  annual  losses due to pathogenic diseases can reach deficits of billions of dollars to global aquaculture. Aggravating this scenario , the increased demand for alternative protein ingredients to replace fishmeal in aquafeeds has led to higher inclusion of plant feedstuffs, and these ingredients may contain anti-nutritional factors and secondary metabolites that can impair the functional competency of the gastrointestinal tract (GIT) against pathogen translocation. Organic acids or acidifiers are promising feed additives that can alleviate these issues by inhibiting the proliferation of pathogenic bacteria in the intestine. They are composed of short- and medium-chain fatty acids with bacteriostatic properties resulting from fermentation of complex carbohydrates by autochthonous bacteria. Their relatively small chemical structures are lipophilic and can diffuse across the cell membrane of gram-negative bacteria, and within the bacterial cytosol, the dissociation of the se molecules acidify the intracellular environment, ultimately leading to ATP exhaustion of the bacteria which inhibits cellular growth and induces death .

The objective of this study was to investigate in vitro and in vivo the supplementation of two organic acids individually as well as in combination  in  a high-plant-protein diet with the carnivorous red drum . A basal diet  was  formulated with soybean products  to provide 75% of  the total crude protein , and  supplemented with  either 0 or 0.5 g kg-1 of butyrate, propionate, or their combination. In the in vitro experiment, digesta was aseptically collected from 16  juvenile fish and incubated under anaerobic conditions with an incomplete anaerobic media supplemented with the experimental diets. After 24 h incubation at 27°C, the samples were frozen and further processed for DNA extraction and the microbial communities were compared among treatments by denaturing gradient gel electrophoresis (DGGE). Results from this trial suggested that the supplementation of the organic acids mildly affected the bacterial community, having a 90% similarity with  that of the basal diet. A 60- day feeding trial  also  was conducted to evaluate if the experimental diets would affect production parameters and intestinal microbial community. Performance of the fish was analyzed as a mixed model, having a 2×2 factorial design (absence or presence of butyrate or propionate as main factors) and the disposition of the aquaria serving as a covariant. Digesta contents were collected  at day 30 and 60 of feeding to compare the microbial communities within treatments by DGGE . The supplementation of propionate to the diet  slightly  but significantly (P=0.02) impaired the growth performance of red drum, and feed efficiency was also slightly  but significantly (P=0.01) impaired by the addition of butyrate. The DGGE results showed that the bacterial microbiome of the gut was significantly affected by the supplementation of the organic acids individually and by their combination, when compared to fish fed the basal diet at the two different collection points. Supplementing organic acids in high-plant-protein ingredients did not benefit the growth performance of red drum. Further investigation of the immunological  parameters  of  fish  plasma and  results for the intestinal DNA for Next Generation Sequencing are pending.

CNPQ: 207141/2014-2