I had a doe due the same day as Angie, miss Buttercup, deliver two huge dead kits over the course of 2-3 days. I also had two does with 4 week old kits, and two does due in 2 weeks. The kits couldn't wait for the pregnant does to deliver; and the does with the older kits didn't have the kind of milk these newborns would need. Their milk would be less fatty and sparse, perfect for kits at 4 weeks old, but not for babies that are only 3 days old. So Buttercup was my only option to saving these babies.
At first, I thought I would just feed them off of her as long as she would allow, and as long as the babies were thriving, and then wean them early at a few weeks old. I didn't trust Buttercup to take the kits. I thought she might attack them or abandon them, since they weren't hers and she had only had dead kits a day before. On the night that I found Angie dead, I nursed the babies on Buttercup for around 10 minutes, to see if she was still producing milk, and Buttercup was not very happy about it. When I nurse babies on a doe, I hold the doe in my lap on her back and put the babies on her tummy. She was still very sensitive after a hard delivery and did not like this at all. After I put her back in her cage, she bit me! She was not a happy camper. That night, I also gave her extra food and calf manna, to encourage more milk production.
The next day, I nursed the babies on her twice and she put up with it. The next morning, when the babies were about 5 days old, I found Buttercup inside her nestbox. I was thinking she may be trying to nurse babies, since her milk was coming more than ever now because of the calf manna, extra food, and stimulation from the kits. So I decided to pop the babies in the box, along with lots of Angie's fur since Buttercup didn't pull very much. I kept a close eye on her, as I fed and watered the rest of the herd. She messed with them a little, by cleaning and smelling them, but was never aggressive. Then they started to nurse, and she looked relaxed and nibbled on hay in the box.
At that point, I knew she would take them successfully. There are a few things that I think I did to prompt her to accept them, even though she did it primarily because she's a great doe. But because I had nursed the babies on her for the first couple days, she had gotten used to the idea of producing more milk and nursing babies. It wasn't weird to her when the babies latched on in the box. And because I nursed the babies on her, it stimulated her teats to produce more milk and told her body that she had babies that she needed to care for. She was ready for the babies when I gave them to her. She had lost 2 kits, but is able to raise 2 kits anyway. And those babies lost a mama but now they have one.
It's a sweet story and the babies are about 2 weeks old now. They are doing fantastic! There eyes have just opened and they are so sweet and docile. Buttercup gets nervous whenever I touch her babies. She's very fond of them and pretty protective.