Front or back leg? If back leg, then yes he needs to be 100% sound. If front, is not such a big issue, provided he's not so lame he can't get about.
Remind me what breed?
We've had
all our Texel and part-Texel tups lame this tupping-time, to a greater or lesser degree. Two of them back leg, so not able to work for part of the time.

You'd think the weather and ground would suit them - not too wet, not too dry.

I don't want to jinx him, but my little Shetland tup lamb has remained in fine fettle...
