No mate, there's no need to. Just let the live rock cycle the tank naturally. Any die off from the rock will produce ammonia to kick start the cycle.
Just keep testing every 24 hours to check.
I think that during the cycle it is producing its own ammonia etc to cycle through whereas if it has already cycled it needs something to feed on hence the prawn, I know nothing mind you...
The prawn would be to keep the LR alive but if you have an ammonia reading then there's no need. A decomposing prawn would eventually produce ammonia for the bacteria on the LR to feed off!