I know that prime slaughter weight for a pig would be around 225 lbs. But, how old is a pig usually to get to that weight. MY two pigs are around 4 months old now. The big one is probably less than 100 lbs (Im guessing), and the little one(which was the runt) cant be much more than 50 lbs. Both look healthy. Both have been wormed with ivermectin. What weight should they be at around 4 months of age? How long to get to 225? We feed them once a day in the evening. They usually have a little bit left the next day when we feed them again and almost never finish all of it. We feed an all-stock sweet feed from tractor supply and mix in some cracked corn with it. They get leftovers maybe once a week.