The gestation period for female sheep is around five months. This means that from the time the lamb is born until it is fully grown, it will take around five months. During this time, the lamb will need to be fed regularly and will grow rapidly. At the end of the gestation period, the lamb will be ready to be sent to market or slaughter. The average weight of a lamb at birth is between eight and twelve pounds. By the end of the gestation period, the lamb will weigh between thirty and forty pounds. The lambs that are born during the winter months will usually be heavier than those born during the summer months. This is because they have had more time to grow while they were kept indoors during the cold weather.