Effects of dietary supplementation with Stachys lavandulifolia Vahl extract on growth performance, hemato-biochemical and innate immunity parameters of rainbow trout (Oncorhynchus mykiss)

A feeding trial was conducted to determine the effects of different doses of Stachys lavandulifolia Vahl (wood betony) extract on growth performance, hemato-biochemical and innate immunity parameters of Oncorhynchus mykiss (rainbow trout). A basal diet was supplemented with 0% (control), 2%, 4% and 8% of S. lavandulifolia extract to obtain four experimental diets. Each diet was randomly allocated to triplicate groups of fish with initial average weight of 16 ± 0.5 g. After 10 weeks of feeding trials, fish fed on diets of 2% and 8% S. lavandulifolia extract had the heaviest weight and highest specific growth rates and average daily growth. The red blood cell count was significantly higher in fish fed with 2% S. lavandulifolia. Meanwhile, the mean erythrocyte cell volume and mean erythrocyte cell hemoglobin content of fish on the 4% S. lavandulifolia diet were significantly higher than those of fish fed the other diets (P > 0.05). Compared to the control diet, white blood cell counts and hemoglobin increased with doses of S. lavandulifolia (up to 4% and 2% respectively). Among the biochemical parameters: blood triglyceride and cholesterol levels were greatest in fish fed 2% and 8% of S. lavandulifolia extract (P > 0.05); while the highest globulin levels were found in fish fed on 4% of S. lavandulifolia. Serum immunoglobulins, alternative complement activity and lysozyme activity increased with increasing herbal inclusion of S. lavandulifolia in the diet. These results suggest that dietary S. lavandulifolia supplementation could enhance the growth performance and innate parameters of rainbow trout.