Goats aggressive towards lamb...

[Nanno]

Yearlings, I've found, are often the most brutal to small newcomers. There are a couple of things you could try, such as building a low platform or a box with a small door that the lamb can squeeze through but the goats can't. You could also try putting a barrier across one area of the pen that has a low gap underneath that once again the lamb can fit under but the goats can't. If he can learn how/when to get away then he should be safe. The girls may also learn not to harass him so badly if they know he's just going to disappear. Good luck!