Essential oil and aqueous extract of basil (Ocimum basilicum) in the diet of pacu (Piaractus mesopotamicus).

This study aimed to evaluate the effects of Ocimum basilicum supplementation in the diet for Piaractus mesopotamicus regarding productive performance, intestinal morphology, muscle residue, and hematological changes after simulated transport stress. Juvenile (23 g±0.08, n = 180) were stocked into 300-L tanks in three treatments and six replicates each: a control diet (not supplemented), a diet with 0.5% essential oil of O. basilicum and a diet with 0.5% aqueous extract of O. basilicum. After 45 days, weight and length were measured, and the fish were submitted to a 4-hour simulated transport to assess the stress responses and the possible effects of the experimental diets on them. The main components of the essential oil were methyl chavicol (70.81%) and linalool (22.04%), while the aqueous extract contained tannin levels of 262.59±24 mg kg-1. The retention rate of the essential oil was about 50%, while the aqueous extract retention varied between 77 and 82%. The results showed no significant effect of basil on the productive performance of the fish. Fish supplemented with the aqueous extract exhibited a lower intestinal mucosal height compared to other groups. Additionally, transported fish showed increased blood glucose concentrations even higher in fish supplemented with the aqueous extract. It was concluded that supplementation with 0.5% basil, either as essential oil or aqueous extract, did not benefit productive performance, intestinal morphology, or reduce transport stress in pacu.