The importance of a bare breech in breech strike was investigated and it was found that it was less important than dags and skin wrinkles. However it does play an important part as it can exacerbate the effect of wrinkles and dags, particularly when these are at lower scores.
Bareness can be scored by using the breech cover scoring system to score sheep prior to hogget shearing.
Culling score 5 animals will also have a beneficial effect on reproduction rate as shown in the following graph. Ewes with low breech cover scores wean more lambs than ewes with high breech cover scores.
Source: DAFWA website Managing non mulesed sheep, Breeding for flystrike resistance in sheep