Effects of dietary purslane (Portulaca oleracea) extract on growth performance, hematological indices and immune responses of rainbow trout (Oncorhynchus mykiss) fry

Inclusion of dietary herbal supplements in aquafeed can be considered as a growth promoter and enhancer of immunity system in preventing various fish infections. Therefore, this experiment was conducted to evaluate the effects of different levels of purslane (Portulaca oleracea) extract (POE) on growth performance, hematological indices and immune responses of rainbow trout fry. The fries with initial weight of 3.3±0.1g were divided into four groups with feeding diets supplemented containing 0% (control, T0), 0.5% (T1), 1% (T2), 1.5% (T3) and 2% (T4) of POE for 56 days. After eight weeks of feeding trail, enriched POE diets significantly increased red blood cell count, white blood cell count, hematocrit, hemoglobin concentration, mean corpuscular hemoglobin (MCHC), neutrophil and monocyte percentages, especially in T3 group compared to the control group (p <0.05). Although no significant differences were observed between eosinophil percentage and MCHC, but lymphocyte percentage decreased significantly (p <0.05). Also supplemented diets with POE significantly increased immune parameters including total immunoglobulin (Ig), IgM, complementary activity, total protein and lysozyme activity in all experimental groups, especially in T3 (1.5% POE) compared with the control group (p <0.05). This study demonstrates POE as a potential immunostimulant to stimulate and improve immune system of rainbow trout fry.