Abstract
This study aimed to evaluate the effects of the phytoadditive Digestarom® on the growth, osmoregulation and hematology and plasma metabolites of Colossoma macropomum. The phytogenic was added to the feed at concentrations of 0 (control), 200, 300, 400 and 500 mg kg− 1 and the animals were fed for 60 days. The results revealed that the fish fed with 400 and 500 mg kg− 1 of the phytogenic additive presented greater weight gain, higher specific growth rate, lower feed conversion rate and a higher condition factor compared to those fed with the control feed. The final length, feed intake, hepatosomatic index and survival rate did not vary between the groups throughout the experiment. The loin eye area was higher in fish fed 400 mg kg− 1 when compared to the control groups, 200 mg kg− 1 and 300 mg kg− 1. Hematological and biochemical parameters did not vary between the groups, except for cholesterol, which decreased in the 400 mg kg− 1 and 500 mg kg− 1 groups when compared to the control group. Glucose, triglycerides and total protein levels remained constant throughout the experiment. Plasma sodium and potassium levels showed an inverse relationship, with a reduction in sodium and an increase in potassium in the 400 mg kg− 1 and 500 mg kg− 1 groups when compared to the control. The enzyme Na+K+ATPase was elevated in the 400 mg kg− 1 group and H+-ATPase was elevated in the 400 mg kg− 1 and 500 mg kg− 1 groups in relation to the control. Thus, our data support that, at 400 mg kg− 1, this phytoadditive, which is based on microencapsulated essential oils, improved tambaqui growth without affecting hematological or physiological parameters. However, ion regulation enzymes indicated osmoregulatory impacts, with increases in potassium and decreases in sodium.