Effects of dietary Persian oak (Quercus brantii var. persica) fruit extract on survival, growth performance, haematological and immunological parameters in rainbow trout, Oncorhynchus mykiss, fingerlings

Abstract

The aim of study was to evaluate the effects of jaft (internal layer of oak fruit) extract on growth, haematological and immunological parameters in rainbow trout fingerlings. A total of 360 fish (average weight 6.25 g, total length 7.75 cm) were randomly distributed in 12 fibreglass tanks (stocking density: 1.04 g L−1) with flow rate of 8 L min−1. The ethanolic extraction of jaft was taken, and, then, a basal diet was supplemented with 0 (control), 0.5, 1 and 2 g kg−1 to formulate four experimental diets. After 8 weeks, blood sampling was performed for haematological and immunological parameters. While immunological parameters such as IgM and lysozyme showed their lowest level in control group, their highest amounts appeared in 2 g kg−1 group. C3, C4 and alternative complement activity increased in fish fed 2 g kg−1 extract compared to control (P ˂ 0.05). Haematological parameters such as white blood cell, red blood cell, haemoglobin and haematocrit were enhanced in experimental groups (P ˂ 0.05). Survival and growth indices did not show significant changes in experimental treatments (P ˃ 0.05). Results indicated feeding rainbow trout with Persian oak extract at 0.5, 1.0 and 2.0 g kg−1 levels significantly enhance the immunological parameters.