279 - Identification of Potential Biomarkers of Reproductive Development in Vaginal Gene Expression Associated with Serum Concentrations of Reproductive Hormones at Key Periods in Gilt Development

Abstract: Early puberty in gilts is associated with long-term reproductive performance. The ability to predict who will achieve early puberty is limited to intensive and invasive collection of serial blood samples to assess reproductive hormones, which is not practical for on-farm use. The objective of this pilot study was to characterize changes in gene expression in the vaginal epithelium related to reproduction during key periods in pubertal development. Pre-pubertal gilts (n =13) in 2 cohorts were followed from 70 d of age until first estrus or 213-215 d of age. Blood and vaginal epithelia were collected at five key timepoints during reproductive development (d70/77, d100/110, d130, d160 and first estrus or end of trial). Total RNA were isolated from vaginal epithelia and relative gene expression of two toll-like receptors (TLR-4 and TLR-5), tacykinin precursor-3 (TAC-3), insulin-like growth factor-1 (IGF-1), and estrogen receptor (ER)-alpha was quantified by real time RT-PCR, relative to the expression of RPLP0. Of the 13 gilts, 3 exhibited estrus early (d169 to 174), 3 were average (d194 to 195), 2 were late (d203 to 213), 3 were deemed anestrus and 2 had a silent estrus (one prior to d160 and one after d200). Statistical analysis of relative expression of each gene relative to 70 d was performed using the PCR package in RStudio (version 1.2.5025). Analysis of gene expression utilized Fisher’s exact t-test for genes TLR-4, TLR-5 and TAC-3, and ANOVA for genes ER-alpha, IGF-1. Expression of IGF-1 and TAC-3 were up-regulated 9-fold and 7-fold, at the start of boar exposure (d 160; P < 0.05). Expression of ER-alpha tended to be upregulated 3-fold at 100 d of age (P = 0.08). Expression of TLR-4 and TLR-5 was not detected for most samples until standing estrus. These transcripts may be putative biomarkers for early estrus detection.