Proof that sheep can't read

It's Spring, so the lambs are coming thick and fast. This one (coyly named '50' and spray painted with her name lest she forget) was sitting under the tree enjoying the dappled evening light away from the rest of the flock. 

Her mother was worried I was getting too close, so she called her back, giving her a comforting drink of milk as a reward. 

But first she gave her a quick sniff just to make she had called the right lamb, which is, of course, proof that sheep can't read....