RE: pie-bald
They are probably genetically inferior from a predator-prey standpointand probablyfrom a herd health standpoint also. Any trait that effects natural camoflague or any predator avoidance mechanism should be aggressively harvested IMO. Uless you would like increased predation and/or hunter harvest in your herd.
The accompanying scoliosis, decreased lower jawand leg length probably aren't traits you want to foster in your herd if you want to look at it from a herd health standpoint.
It may be a homozygous recessive gene but it's supposedly more common than albino and I'd recommend you harvest them if you come across them.