Short-term effects of feeding powdered Aloe vera (Aloe barbadensis) and nettle (Urtica dioica) on growth performance and stimulation of innate immune responses in rainbow trout (Oncorhynchus mykiss)

To evaluate the nutritional impacts of powdered Aloe vera and nettle plants on growth performance and some parameters of immune response in rainbow trout, a total of 462 fish with an average weight of 10.80 ± 0.59 g were obtained from authentic fish farms. The fish were fed in seven groups with diets containing 0.5, 1, and 1.5% of Aloe vera powder and 0.5, 1, and 1.5% of nettle powder, and also a control with a basal diet without herbal supplementation for 4 weeks. The results of fish biometry showed that dietary supplementation with the powdered plants led to significant differences in weight gain, specific growth rate, feed conversion ratio, and feed efficiency ratio with 1.5% of Aloe vera and 0.5% of nettle supplementations compared with the control group. The treatments displayed increased hematological parameters as well as serum biochemical parameters. Serum lysozyme and complement system activities elevated due to dietary supplementations with the best results found in treatments with 1.5% of Aloe vera and 0.5% of nettle. However, despite an increase in respiratory burst activity of leukocytes in fish fed with powdered plants, no significant differences were observed as opposed to the control.