The intestinal health of silver catfish Rhamdia quelen can be changed by organic acid salts, independent of the chelating minerals

Food additives based on organic acids or their salts promote numerous improvements in zootechnical parameters, digestive enzymatic activities, resistance to diseases and intestinal health. This study aimed to evaluate the influence of calcium and sodium chelated to propionic acid on the digestive enzymes activities, intestinal microbial community and histological alterations in the liver and intestine of the silver catfish Rhamdia quelen. Fish with an initial mean weight of 8.43 +/- 0.18 g were divided into a control and four treatments, with 15 fish in each replicate, and fed the following supplemented diets for 60 days, four times per day: unsupplemented control, Ca-propionate 0.25% (Ca-0.25%), Ca-propionate 1% (Ca-1%), Na-propionate 0.25% (Na-0.25%) and Na-propionate 1% (Na-1%). At the end of the assay, digestive enzymes activities in the gastrointestinal tract (GIT) was not affected by the chelating mineral, nor by its concentration to propionic acid. On the other hand, the most important digestive enzymes for silver catfish were lipase and acid protease. Regarding the intestinal microbial community, fish fed Ca-0(.25%) showed a lower concentration of total heterotrophic bacteria and a higher lactic acid bacteria count, compared to Na-1%-supplemented fish, in addition to the maintenance of cordonal features and liver cholestasis. Fish fed a Ca-0(.25%) or Na-0(.25%) supplemented diet presented the best histomorphometry parameters, such as the greatest width and number of villi, a lower number of eosinophilic infiltrates and the absence of lymphocytic infiltrates. The organic acid propionate chelated to calcium at 0.25% improved the microbial composition and intestinal health of silver catfish, with no effects on the liver, the most important organ for depuration, and could be indicated as a feed additive for silver catfish.