I have heard of western hogs as small as 150 grams breeding successfully, and I have bred 200-215 gram hogs myself. However, I generally use 250 grams as the "target weight." It's not going to hurt to wait until they are 250, and they seem to have fewer complications, and bounce back faster after laying when they are a bit bigger. On an appropriate feeding schedule, you should be able to breed most females on their second spring. My holdbacks from 2013 are between 70 and 90 grams now, and will easily reach 250 before december when I put them down.