One of our first time mothers just doesn't have enough milk for her new lamb. Luckily I had frozen some milk in previous years from ewes that had enough to spare. Her lamb was grateful the first time I offered a meal from such a strange new source. Some lambs simply refuse to take anything that doesn't come directly from a ewe even though they really are hungry for more.
This lamb has been drinking a little less from the bottle each day as its ewe is slowly producing more and more milk. And that's a relief because my frozen supply is running low.