samirich gave a Tune for "Whose pigs".
Did the G mean the same as g etc. (I remember it as being all on thr 6 notes between D & B
I've not heard it as a round, but many years ago someone sang it on the BBC radio 2 folk programme and it took my fancy.
I have been singing the second line as
B      B    A   B
whose pigs are these
That may be my memory at fault (the folk process?), and I dont know if it would work as a round.