Yes it's unfortunate that some of our best bits of twisty road cross open land where this can be a danger especially in springtime. A shame really because the lack of hedges allow good visability. Watch out especially for lambs seperated, by the road you are on, from their mothers . They will choose the moment of most panic (ie just when you are nearest to them) to dash across. Be aware they are especially dangerous when sandwiched against a barrier (hedge, fence, bank etc on one side), same thing happens. In the evening after a sunny day stock is often attracted to the warmth retained by the tarmac. I don't think you can claim from the farmer but that he could claim from your insurance for the 'value' of the lamb. Sorry about the damage to yourself and your bike. It could have been worse, on Dartmoor you have the ponies and in Scotland deer (at night).