Dietary supplementation with Ocimum gratissimum essential oil improves the intestinal bacterial populations of Piaractus mesopotamicus

The aim of this study was to evaluate the effects of the dietary supplementation Ocimum gratissimum essential oil (EO) on pacu (Piaractus mesopotamicus) intestinal microbiota and morphometry. In this study, juveniles of P. mesopotamicus were fed with diets supplemented with 0.5 and 1% of Ocimum gratissimum EO for 30 days. At the end of this period, the intestinal microbiota of the pacus was relatively quantified through qPCR, and the intestinal morphometry was evaluated using histometric methods. O. gratissimum EO feeding supplementation at 1% significantly altered the intestinal microbiota of juvenile pacus, resulting in higher relative quantification of bacteria from the genera Enterococcus and Bacillus when compared to 0.5% and control groups. O. gratissimum EO feeding supplementation presented no effects in intestinal morphometry. Our results suggest that the feeding supplementation of P. mesopotamicus with O. gratissimum at 1% concentration during 30 days modulates the intestinal bacterial populations but do not cause any changes in intestinal morphometry.