Lipidome profiles of postnatal day 2 vaginal swabs reflect fat composition of gilt’s postnatal diet

We hypothesized that postnatal development of the vagina is impacted by early nutritional environment. Our objective was to determine if lipid profiles of vaginal swabs were different between gilts suckled by sow or fed milk replacer the first 48 h postpartum, with and without a lard-based fat supplement. Gilts (>1.3 kg) were selected at birth across 8 litters and assigned to treatments: colostrum suckled (S, n=8); S plus fat supplement (SF, n=5); bottle-fed milk replacer (B, n=8); or B plus fat supplement (BF, n=7). At 48 h postnatal, vaginal swabs were taken with a cytology brush, immersed in ultrapure water to burst cells, and lipids extracted for analysis using multiple reaction monitoring (MRM)-profiling. Lipids extracted from serum collected at 48 h from gilts and milk collected from sows at 24 h were also analyzed with MRM-profiling. Receiver operating characteristic curve analysis found 18 lipids highly distinguished [area-under-the-curve (AUC) > 0.9] between S and B gilts, including phosphatidylethanolamine with 34 carbon and four unsaturations in the fatty acyl residues [PE(34:4)]. Twelve lipids from vaginal swabs highly correlated ( r > 0.6; p < 0.01) with nutrition source. Lipids more abundant in milk replacer drove association. For example, mean intensity of PE (34:4) was 149-fold higher in milk replacer than colostrum, with 1.6- and 2.12-fold higher levels in serum and vaginal swab samples ( p < 0.001), respectively, of B versus S gilts. Findings support that vaginal swabs can be used to noninvasively study effects of perinatal nutrition on tissue composition. Summary sentence Vaginal swab lipidome profiles at 48 h reflect the fat composition of neonatal diet during first two days postnatal.