We usually only end up with one, maybe two bottle lambs a year lambing out 40-50 ewes. For just one, I usually end up bottle feeding it. However if I do end up with more, I prefer a lamb bar bucket. It is a huge time saver as you only have to fill it once a day. Lambs grow well on the free choice cold milk replacer.
I strongly prefer the Pipestone milk replacer over all others I have tried.
As far as culling factors for ewes, any ewe that rejects a lamb would be gone. I have no tolerance for ewes that won't raise their own babies fortunately, in 17 years lambing, I have only had that occur once. A ewe that is fed well but doesn't have enough milk for her lambs is also gone. Aside from that, it comes down to quality. Since we are raising show lambs, a ewe that does no raise show quality lambs is moved out. We do also sell good ewes every year simply to make room for our keeper ewe lambs. These ewes are normally our older genetics, often very good proven mothers, but since we have to keep moving forward, they are sold.