LAUSR

Abstract Essential oils as food additives have the potential to increase the efficiency of nutrients in the diet of fish. The effect of essential oil of Zingiber officinale (EOZO) as a nutritional additive for Nile tilapia juveniles (Oreochromis niloticus) was evaluated. Five diets were evaluated (in quadruplicate) with increasing levels of EOZO (0.0, 0.5, 1.0, 1.5 and 2.0 mL kg diet−1) over 60 days. Zingiberene was the main constituent of EOZO (33.20%). Supplementation with 0.5 mL EOZO kg diet−1 improved growth performance and feed conversion rate. Fish fed EOZO diets improved leukocytes and haematological values and plasma cholesterol levels. In general, the increase of EOZO added in the diets increased hepatocyte number and reduced intestinal villus width and height and hepatocyte area and perimeter. Liver dysfunction was found in fish fed EOZO concentrations above 1.0 mL kg diet−1. In conclusion, the supplementation with 0.5 mL EOZO kg diet−1 could be indicated for Nile tilapia, as it improved growth performance, intestinal villi size and haematological variables, without compromising metabolism and hepatic histomorphometry.