i never pre-shrink a batting- i purchase the batting that is right for my project- the shrinkage in most batts is so minimal- and dependant on so many things---
but no---never just toss a batt into a washing machine- that is not quilted and bound- what would come out would be a pretty traumatic sight!
read the packaging when you buy a batt- and pick the one that works for your project- there are even wool batts on the market that do not shrink as much as a cotton batt (like mountain mist)
shrinkage depends on the amount of quilting done on the quilt also