When the first bulls from Canada were selected they were from the closed herd book . They may not have been 100% by every country's standards but they were a very high percentage pure. They needed to qualify as 100% at the time because the majority of UK cattle were very high percentage Maine Anjou. This had resulted in complaints from the Maine Anjou Society that had pointed out there was a herd book for Maine Anjou cattle. When the Shorthorns in the British herd book were looked at it was found the percentage of Shorthorn blood was lower in most cases than that of Maine Anjou blood and this resulted in the Shorthorn breed being classified as a rare breed. I believe there was some kind of subsidy to help with quarantine and shipping costs of bulls for rare breeds. (this is how I remember the initial shipments, if someone has better info on the program please share)