20 Using anogenital distance, a prenatal marker of androgen exposure, to predict pregnancy by artificial insemination in yearling beef heifers

Abstract Anogenital distance (AGD), distance from the anus to the clitoris is programmed during fetal life by testosterone concentrations. In rodents, fetal testosterone increases AGD and reduces reproductive performance in the adult life. We hypothesized that yearling beef heifers with a shorter AGD during the gynecological examination have a greater probability of pregnancy by artificial insemination (AI) than heifers with longer AGD. Yearling heifers (n = 554) were submitted to estrous synchronization, gynecological examination (pre pubertal vs. pubertal) and AGD measures to the top of the clitoris (AGD-C) or to the dorsal commissure of the vulva (AGD-T). At CIDR withdrawal, heifers received an estrus patch. AI was conducted using 5 bulls. 30 days after AI pregnancy diagnosis was performed. 85% of the heifers were pubertal and 62% displayed estrus. AGD-C and AGD-T were positively associated (P < 0.001, R²= 0.1982). For each unit of increase in body weight AGD-C increased 0.0064 cm (P = 0.0003). AGD-C was positively associated with the probability of puberty (P = 0.0019) and pregnancy in heifers without a corpus luteum upon gynecological examination (P = 0.10). ROC curve analysis found a poor area under the curve (0.59) for any AGD to predict pregnancy/AI. In conclusion, it looks like in adult life the AGD effects on fertility are mostly a consequence of the increase in body weight the prenatal effects on the AGD are diluted over time and are not associated with reproductive outcome in adults.