My sheep have been lambing since November with the most recent 2 days ago. I have 5 more ewes that are close. I have covered birthing stalls in the sheep barn with heat lamps over the water buckets to keep them from freezing and to provide heat for the lambs. During the day I lock the other sheep out of the barn and mingle the ewes and older lambs. When I feel they are old enough to get out of way of the feeding stampede, I introduce them to the flock. That said, My question is: How old does a lamb have to be before he can be subjected to sub-zero weather, where their bodies can regulate their body temps sufficiently? I've been raising Jacobs sheep for 8yrs and still don't know! I used to plan for spring lambing but wanted to try the fall/winter lambing a couple of years ago and the lambs have been heathier and hardier with the cold weather lambing.