The next generation might have throw-backs to the parent or grandparents. Those birds are inbred, as another poster mentioned. They are sometimes a dwarf, or slow-growing, to add some genetic factor to the final bird. You will want to hatch a lot to get good birds, and cull out the small or undesirable ones. They do not reproduce what the birds you bought are -- but a lot of them will have the same qualities as the broilers you bought. Do you want them for starting your own home-grown meat bird line, or just to eat? That makes a difference. If just to eat, you will save time by just buying more chicks. If you want the genetic line to raise your own, it will take generations.