Zinc as an essential micronutrient in organisms and natural environments plays an important role in many biological activities. In this study, the effects of feeding with different sources of zinc supplements on seminal biochemical and enzymatic changes and quality and quantity indices of sperm in rainbow trout (Oncorhynchus mykiss) were investigated. A total of 108 broodstock males in four treatments were fed diets supplemented with 40 mg kg−1 of: 1. Mineral zinc (ZnSO4), 2. Zinc nanoparticles (ZnO-NPs), 3. Organic zinc (Zn-proteinate, Bioplex Zn®) and 4. A diet containing no extra added zinc as control for 16 weeks. Sperm motility duration and spermatocrit percentage were higher in treatments supplemented with all zinc sources than the control group (P < 0.05). After evaluating the quantity and quality of semen, fertilization was performed for different groups using female eggs of control group. The highest rates of fertilization, eyeing and hatching were obtained from treatment 1. Treatment 1 also yielded the highest offspring survival rate. The lowest levels of AST, ALT, LDH and SOD enzymes and the highest values of magnesium and calcium ions were observed in seminal plasma of fish in treatment 1. Seminal plasma levels of cholesterol, urea, glucose and total protein were at the lowest in treatment 1, however only the levels of glucose and total protein in the treatments showed significant difference (P < 0.05). Present results indicate that dietary mineral zinc has a prominent potential in improving sperm and seminal plasma quality indices and reproductive performance in broodstock males of rainbow trout.
