Although LAI yields high pregnancy rates, double-horn insemination is time-consuming and labor-intensive. It would be more efficient if LAI could be performed unilaterally while pregnancy rates similar to that of bilateral insemination. To evaluate whether spermatozoa that are deposited into only one of the uterine horns can migrate transuterinally, this study used spermatozoa that were stained with supravital fluorochromes. Fluorochrome-stained spermatozoa have been used to study sperm distributions, motilities, sperm binding, and fertilization in several species, including sheep [17], rabbits [23], cattle [24] and [25], cats [26], fowl, and turkey hens [18]. In this study, the spermatozoa were labeled with either the CT-Green or CT-Red fluorochrome. These nontoxic dyes have different emission/excitation wavelengths, and therefore cannot be observed simultaneously