They're just the holes where the sacks were sewn and yes, they will wash out somewhat. Feed sacks were sewn with very thick cotton thread similar to what is used on large bags of dog food. My mom and grandma used to save that thread for everything from tying packages, to braiding for shoelaces, to tying quilts. They're valuable to collectors when kept whole but they're valuable to quilt collectors when put into a quilt. Just make sure that you use appropriate fabrics and thread with them. We used to have community picnics in the spring and all the farm wives would bring their feed sacks to swap and trade so that everyone would have enough of each print to make an outfit. I was pretty young back then but I vaguely remember the stacks of cloth on the blanket.