Poor wee lambs

I was glad to get out for a walk this afternoon even though it was trying hard to rain. I passed this notice on a gate and it made me think:

1. Is it an instruction for us not to let any lambs into the field? (Most grammatical)
or
2. Has a comma been omitted and it's an instruction to any passing lambs to stay out of the field? (Most unlikely)
or
3. Has an exclamation mark been omitted and it's an instruction for us not to enter the field because there are lambs in it? (Of course!)


Call me pedantic if you like, but it gave me something to mull over on my walk.