In all my years for raising sheep I've still never heard one say 'baa'.
What I hear them say is 'maa'.
Here's Wee Tiny Lamb, photo taken last evening when I brought the flock in from pasture for the night.
He's doing quite well, though I suspect he'll be old enough to drive by the time he gets to the size of the other lambs.
He doesn't say 'baa'.
He doesn't even say 'maa'.
Even his vocabulary is wee tiny...