If you see scurs in a Bos taurus female, it came from BOTH sides of the pedigree. One copy will produce scurs in a male, but two copies are required in a female.
Furthermore, since two copies of the genes are required in a female, and given the random assortment of genes, scurs would only present themselves in 1 out of every 4 females born to a heterozygote male and females. Therefore, if you are seeing greater than 25% scurs in these females, there was something going on. Scurs might "pop up" occasionally, but with a track record of even 25%, that implies that every dam carried a copy.
Also, one copy of the scur gene is all it takes for bulls to present scurs. If these heifers had scurs(requiring 2 copies), so did their sires!! That is a biological fact, as we understand the transmission of the scur gene at this point in time.
Scurs were naturally occuring in Angus, and were fairly well eliminated by the mid 1960's or thereabouts.
Badlands