Yes, yes, yes, by all means read the instructions before pretreating batting. The instructions on the bag are pretty clear for Hobbs 80/20 for the look you are wanting. But in any case it is important not to put it through an aggitating cycle because it can just tear apart and you could be left with shreds. Worse yet, you could have bits and pieces of the batting flush through your washer and have a repair bill or new machine shopping in your future.
If there are no pretreating instructions, assume you cannot pretreat the batting.