An apparatus for mixing and pumping manure slurry from a manure pit comprises a pump unit having first and second mixing rotors and a pumping rotor. In operation, the first mixing rotor draws solids downwardly towards the pump unit while the second mixing rotor redirect a portion of the solids drawn by the first mixing rotor away from the pump unit, thereby allowing to control the ration of solid contents in the slurry pumped by the pumping rotor. A non-diverted flow distribution arrangement is also provided for selectively connecting the pump outlet in straight-through flow connection with either a drainage pipe or a re-circulation pipe.