Kirk: Since Shorthorns helped form the foundation of Dexters in 1890-1930, and since the Peerless Dexter herd in America likely has lots of Shorthorn genetics from the Peerless Shorthorn herd, then any small additional amount of shorthorn DNA coming into Dexters in the 1960's would have no impact, since those genes were already in Dexters.
Shorthorns and Dexters likely share 99.999% of the same genes. There are likely only a tiny few genes in Shorthorns that you couldn't already find somewhere in the "purest" of Dexters, and remember too that the "purest" of Dexters likely have a good number of Shorthorns in their backgrounds in the Dexter foundation stock.
There is absolutely nothing that confirms this speculation Kirk has posted. Here is a copy of a page from the book published by DCS titled, " Symposium" which presented the presentations of those who contributed at that meeting which honored Beryl Rutherford. This page is taken from the presentation of Tim Bray, PHD, who conducted the Cardiff project with the Dexter breed. For clarifiction, the term "traditional Dexters" as relates to the English bloodlines is different than the term as used by the US preservation breeders which defines traditional by pedigree. Ypsitty along with Woodmagic were two early herds and the American Dexter samples were all Dexters with Legacy pedigrees except for the one sample sent of Parndon Bullfinch.
BRAY Presentation.pdf (840.77 KB) ( This same information can be found in the Cardiff project published papers as well).