Lactoferrin is a spiral glycoprotein with multi biological functions. In this study unmatured molly fish ( Poecilia sphenops ) fed diet containing lactoferrin in 0, 200, 400 and 800 mg/kg for 15 weeks. This experiment conducted in completely random design in triplicats. At the end of experiment growth and survival indexes, digestive system bacterial fauna, intestine histology, survival rate for broodstocks after exposing to air, some reproduction indexes and non-specific immunological parameters and finally cortisol level as a stress indices in embryo were investigated. Results showed no significant difference in survival and growth rate (P 0.05). Fish fed on 200 mg/kg lactoferrin showed highest level of total counted bacteria in comparision to other groups (P 0.05). According to results of histological examination, Intestinal villus height, villus height to diameter, enterocyte diameter, cavity diameter and villus height to cavity diameter in 200 and 400 treatments showed significant difference in comparision to control group (P 0.05). Highest rate of broodstocks with embryo with significantly difference was observed in 200 treatment (41.37±7.82%) and lowest observed in control treatment (13.09±7.24%)(average±standard error) (P 0.05). Feeding with lactoferrin caused to significant increase in absolute and relative fecundity in compare with control group (P 0.05). Embryo weight index showed no significant differences between treatments (P 0.05). Highest cortisol level in embryo with significant difference belonged to 200 treatment and lowest belonged to control and 400 treatments (P 0.05). Results of immunological parameters showed there is a significant increase in lysozyme and ACH50 levels in embryo of broodstocks fed by lactoferrin different levels in compare to control treatment (P 0.05). In conclusion results showed 200 mg lactoferrin in diet has possetive effect on different indexes of molly fish and recommended as supplement in the diet of this fish. Keywords: Growth , Immunology, Stress, Reproduction, Lactoferrin
