It has been difficult to evaluate critically the accuracy of insemination. For many years the dye method was used to evaluate the proficiency of professional technicians. Excised reproductive tracts were inseminated with a biological dye in place of semen. In some cases live cows were inseminated with dye and the tracts were examined immediately after slaughter. The location of the dye within the tract indicated the site of semen deposition.
Nonreturn rate is an indirect measure of fertility.
Technicians with a nonreturn rate greater than 78 percent achieved 86 percent of their dye depositions in the uterine body and they had no extrauterine inseminations. Inseminations by technicians with nonreturn rates below 70 percent resulted in only 34 percent of the dye depositions in the uterine body and 31 percent extrauterine inseminations. It appears that accurate semen deposition is correlated with successful pregnancy rates. There are limitations to the dye method. The location of the insemination rod tip cannot be determined and manipulation of the reproductive tract during slaughter or dissection can distort the distribution of the dye.