Haven't used one myself - we tend to rely on creative fostering - but how many lambs are sharing a teat? They soon cotton on if there's competition for what's available.
We had 7 lambs sharing 2 teats but put a 3rd teat on the bucket about a week ago. Now I've got the 5 lambs on the 3 teats, all have taken to it first time since I put it in this morning.
SallyintNorth we tried to keep it with milk in 24/7 but it was virtually impossible unless we kept refilling it every 2 hours... they are very gutsy though especially 2 of them... never have I seen a lamb drink as quick and as fast as they do! I was filling it with 6 litres between the 7 of them every evening in an attempt for it to last well into the night, bearing in mind they are in theory meant to be on 1.5 litres a day. They drank about 2/3 of it as soon as it went in but left a good amount in the feeder and lay down... fantastic I thought, they should have enough to see them through the night especially as they've just had a good tummy of milk- 2 hours later they had polished off the other 1/3.
I just put my head in on the 7 older lambs and through the bleeting when they saw me, they had mouthfulls of creep, something I guess if they were on an ad lib feeder which is always full they would not be doing as they would still be full of milk.
It's a useful thing to have though especially for the really young lambs on 4 or 5 feeds a day, saves a lot of early mornings and late nights, they develop a lot quicker over the first 3 1/2 weeks and are better covered, not pot bellied, and they don't tend to empty it and do drink little and often.