44 Identification of Vaginal Gene Expression Differences in Gilts Achieving Early or Late Puberty

Abstract

Abstract A known predictor of reproductive success in swine breeding herds is age at puberty. Early puberty is associated with improved long-term reproductive performance. Additionally, it has been established that vaginal gene expression in gilts changes throughout reproductive development. The hypothesis was that vaginal gene expression was correlated with estrus expression and therefore likelihood of reproductive success. Pre-pubertal gilts (n = 29) were followed from 70 d of age until first estrus or 215 d of age. Vaginal epithelia were collected using a swabbing technique at five key timepoints during reproductive development [70 (on farm arrival), 100 (mid-folliculogenesis), 130, 160 d of age, and first estrus or end of trial]. Boar exposure began on 160 d of age with 15 minutes of fenceline contact at 0700 h daily with trained technicians observing for signs of standing estrus (i.e., erect ears, swollen, pink vulva, allowing back pressure). By 215 d of age, 19 females were classified as expressing estrus early (160 to 181 d), 4 were average (181 to 202), and 6 were late or as anestrus (202 to 215 d). A subset of 5 gilts that expressed estrus early and 5 gilts that expressed estrus late or as anestrus were used for further investigation of vaginal gene expression. Total RNA was isolated from vaginal samples at 3 timepoints (100, 130, and 160 d of age). Samples were sent to a commercial genomic sequencing laboratory for RNA sequencing. Each gene was scaled individually so that all genes were on the same scale for comparison, and the Welch two sample t-test was applied to determine statistical differences. A total of 53 genes were differentially expressed between the early estrus and late estrus or anestrus groups. Data were further screened to identify genes that were expressed in at least 3 gilts in either the early estrus or late estrus group at a given time point; this subset of 26 genes were selected for direct comparison at each time point. At 100 d of age, late estrus gilts had increased expression (P = 0.05) of a gene commonly found in females with polycystic ovary syndrome. At 130 d of age, genes associated with the innate immune response had greater relative expression (P < 0.05) in gilts expressing early estrus. At 160 d of age, genes associated with fat cell deposition had greater relative expression (P < 0.05) in the early estrus expression gilts. Distinct differences in transcripts during reproductive development may be putative biomarkers for detection of early estrus in pre-pubertal females.