One abattoir I used said no food on the morning, I answered with the same thing as Benkt, how do you load a pig without food?
And the routine is now the same as Daisy's mum and Bionic, to load the night before. It gives the pigs time to calm down, and you haven't got the worry on the morning of being late etc etc. Way I see it they can have their final meal in peace, I usually chuck in some treats and if it's one pig going alone I back it up to another pen of pigs and leave the ramp down (with inner gate secured) so they can see their friends.
One thing I did with my first lot was leave the trailer accessible to their pen for several days and feed them in it every time, they soon get the idea! I have been lucky since then as most pigs have been well behaved but I have some Iron Age finishers who are so wary of anything new I'll have to resort to trying that again.