Impacts of different levels of vitamin K on the growth performance, hematological parameters, and immunological response of juvenile Nile tilapia (Oreochromis niloticus)

The current investigation was carried out to determine the impacts of different levels of vitamin K (VK) on the growth performance, hematological parameters, and immunological response of all-male juveniles of Nile tilapia (O. niloticus). VK3 (menadione) was added in five concentrations (0.0, 2.0, 4.0, 8.0, and 12.0 mg kg(-1) diet) in five isonitrogenous (30% cp), isocaloric (18.61 MJ kg(-1)) diets. The fish were fed the diets at a daily rate of 3% of their live weight, divided into 3 meals for 60 days. The results implied that supplemental VK did not provide any growth rate improvements and the efficiency of feed utilization over the control diet. Increasing dietary VK above 2 mg kg(-1) feed resulted in significant retardation in fish performance and survival rates. Furthermore, supplemental VK up to 2-4 mg kg(-1) increased hematological parameters, physiological functions, immune response, antioxidant capacity, and bone mineralization. Further increase in dietary VK resulted in a significant decline or level off in these parameters. Meanwhile, liver function enzymes increased progressively with dietary VK increasing. In conclusion, these findings suggest that supplemental VK maybe not be necessary for Nile tilapia growth performance, whereas about 2-4 mg kg(-1) diet is required for other physiological functions. Increasing VK beyond these levels may pose adverse effects on Nile tilapia. However, further long-term studies are required to confirm these results.