Sire Conception Rate (SCR) is the industry standard for comparing bull fertility. SCR is measured independently by CBCD, who are the same organisation that publish the US Sire Summaries. The data is calculated based on the results of pregnancy checks carried out by veterinarians. SCR is not a genetic trait-it is a measure of the fertility of the bull's semen in practise. It is influenced by semen quality, lab expertise, semen concentration, and, by knowing what needs to be discarded, and actually discarding it.