PSI-A-9 A Comparison in Vaginal Gene Expression and Circulating Hormone Concentration in Pre-Pubertal Gilts Achieving Puberty at Different Ages

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 and more high-quality offspring. The objective of this study was to compare vaginal gene expression in gilts that achieved estrus early (160 to 181 d of age), average (181 to 202 d of age), late (202 to 215 d of age) and anestrus. Pre-pubertal gilts (n = 13) were followed from 70 d of age until first estrus or 214 ± 1 d. Vaginal epithelia was collected using a swabbing method at five time points during reproductive development [70 (on-farm arrival), 100 (mid-folliculogenesis), 130, 160 (start of boar exposure) d of age and standing estrus or end of trial]. At 140 d of age, females received an indwelling titanium catheter for daily blood collection during boar exposure. Following detected standing estrus, a blood sample was collected every 2 hours for 96 hours to characterize the peak serum concentration of luteinizing hormone that occurs at ovulation. At the conclusion of the trial, 3 gilts displayed early estrus (169 to 171 d of age), 3 gilts were deemed average estrus (194 to 195 d of age), 3 gilts were deemed late estrus (203 to 213 d of age), 3 gilts were deemed anestrus and 1 was identified as having a ‘silent’ estrus after 200 d of age. Total RNA were isolated from vaginal epithelia and relative gene expression 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. to D70 was preformed using the PCR package offered in RStudio (version 1.2.5025). There was an increase in ER-alpha expression in the average estrus group (P = 0.03) at 130 d of age. Early estrus females had a greater expression of IGF-1 at 130 d of age compared with anestrus females (P = 0.01). Of the 9 females placed with an indwelling catheter, 2 catheters were nonpatent, and blood sample could not be collected at standing estrus. Of the 7 females where blood sample was collected at standing estrus, all females achieved an luteinizing hormone (LH) peak within 12 h after recorded standing estrus. Identification of key differences in the vaginal epithelium in concert with LH values provides biological evidence that those deemed achieving estrus based on behavior did successfully achieve estrus. These vaginal epithelium differences may serve as putative biomarkers to detect early estrus in pre-pubertal gilts.