When do lambs grow up?

Charlotte had 8 of her mates round last night for a belated birthday celebration (It mainly consisted of watching 'Mamma Mia' and being incredibly noisy ...), so Bethany and I escaped for a walk with Jackson.

As it's spring, the field next to the train station is full of sheep and their new-born lambs - Bethany loves lambs. She wants one for her birthday, and she plans to keep it in her bedroom and will put back in the field when it's big and grown up. She also wants a rabbit and a hamster, and won't be getting any of them!

Whilst we stood and watched the lambs, I was surprised to see them playing. It definately looked like they were playing chase, which lead Bethany to ask when do lambs grow up and stop playing games? And I have no idea ... We know that 1 human year is the equivilent to 7 years for a dog, but what is it for sheep? Answers on a comment please ...

B did tell Mia about the lambs earlier this week (We've been up most nights to watch them), and Mia told her how she likes a nice bit of roast lamb. But, according to Bethany you don't get roast lamb from the lambs you see in the fields, oh no ... apparently it comes from 'turkey lambs', which are turkeys that taste like lamb. B is of the opinion that anything that looks like a turkey in real life is certainly not good enough to eat, and that those 'gamboling' lambs (Her new word) are way too nice to eat. So there ...