Little and often is best, if that's practical for you. If they have loads in front of them, they tend to pull it out and waste it. If they're ready for it when it arrives, they get on and eat it all up!
Edited to say that of course it is important to make sure that every animal has access to it when you do put it out - which usually means having
considerably more room than the number of heads would warrant, as the bossier ones will bully the weaker ones away from 'their' hay.
