Growth, hematology, metabolism, and oxidative parameters of silver catfish (Rhamdia quelen) fed diets containing Lippia alba leaf

Abstract The dietary addition of Lippia alba essential oil has been studied in fish, showing excellent results against lipid peroxidation. The objective of this study was to evaluate the compounds present in the plant and the growth, hematology, metabolism, and oxidative parameters of silver catfish fed diets containing L. alba leaf. The experimental design was completely randomized with 500 silver catfish distributed in 5 treatments and 4 replicates in a water recirculation system. The treatments tested were: control (without leaf inclusion); 0.5; 1; 1.5 and 2% inclusion of L. alba leaf powder. All diets tested had the same composition matrix, containing 37.49% crude protein and 10.04% lipids. Leaf compounds have been found that may have great antioxidant capacity such as caffeic acid, verbascoside, and calceolarioside E. However, some compounds present in the leaf may cause damage to fish performance such as malic acid and quinic acid. Fish fed diets containing L. alba leaf presented lower growth and changes in hematological parameters compared to control fish. At the higher levels of L. alba leaf inclusion, undesirable metabolic changes occurred as increased plasma alanine aminotransferase activity, indicating liver damage. The presence of L. alba leaf in diets resulted in decreased muscle lipid peroxidation and increased the amount of non-protein thiols in the gills and muscle. This indicates that the plant leaves have antioxidant potential in fish. Therefore, at the tested levels, the addition of L. alba leaf powder in diets for juveniles of silver catfish is not recommended. Summary statement This article is interesting because it assesses the inclusion of natural products in fish diets, resulting in improved health.