Genotypic differences in placental development during late gestation between Chinese Meishan and White crossbred gilts in response to intrauterine crowding

Authors: Miles, Jeremy; Vallet, Jeff

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2018
Publication Date: 7/10/2018
Citation: Miles, J.R., Vallet, J.L. 2018. Genotypic differences in placental development during late gestation between Chinese Meishan and White crossbred gilts in response to intrauterine crowding [abstract]. In proceedings: Society for the Study of Reproduction 51st Annual Meeting, 10-13 July 2018, New Orleans, LA. p. 25-26. Available: https://www.ssr.org/sites/ssr.org/files/2018_annual_meeting_abstracts_updated.pdf

Interpretive Summary:

Technical Abstract: The porcine placenta is classified as non-invasive, epitheliochorial in which hemotrophic (i.e., capillary) exchange is maximized during late gestation via modification of the folded bilayer consisting of an intact uterine epithelium and trophectoderm embedded in loose stroma that increases in width and complexity. Histotrophic (i.e., glandular) exchange occurs via placental areolae juxtaposed to the uterine glandular epithelium. The objective of this study was to evaluate placental development during late gestation between prolific Chinese Meishan (MS) and White crossbred (WC) gilts following intrauterine crowding. To induce intrauterine crowding, similar aged MS (n = 7) and WC (n = 5) gilts were unilaterally hysterectomized-ovariectomized at approximately 60 days of age and allowed to recover prior to breeding (<200 days of age) with sires from the same genotype. At day 100 of gestation, the remaining uterine horn was recovered via laparotomy and hysterectomy. All fetuses were weighed to identify the smallest and largest littermates within each litter. Intact uterine and placental attachment sections were obtained from the antimesometrial side of the uterus of the smallest and largest fetus within each litter. Sections were processed for histology and the folded-bilayer and stromal morphology were analyzed using computer-assisted morphometry. In addition, the entire placenta of the smallest and largest fetuses within each litter were imaged to assess gross morphology and areolae density. All data were analyzed using MIXED model procedures for ANOVA. Ovulation rate was greater (P = 0.03) in MS gilts compared to WC gilts. However, there were no differences (P > 0.38) in uterine capacity, fetal survival, fetal and placental weights or placental efficiency (fetal to placental ratio). In contrast, allometric growth relationship between fetal and placental weights was decreased (P = 0.01) in MS gilts compared to WC gilts indicating a greater fetal sparing effect within the MS breed. The width of the folded bilayer was greater (P < 0.01) in placentas from WC gilts compared to MS gilts, irrespective of fetal size. Placentas from small fetuses had greater (P < 0.01) folded bilayer width compared to placentas from large fetuses, irrespective of gilt breed. The stromal width was greater (P < 0.01) in placentas from large fetuses compared to small fetuses, but stromal width was not different (P = 0.29) between breeds. However, the difference between stromal width in placentas between small and large littermate fetuses was greater (P = 0.05) in WC gilts compared to MS gilts suggesting limited response to fetal crowding in MS gilts. There was a breed by size interaction (P < 0.01) for areolae density in which placentas from large MS fetuses had greater areolae density compared to small MS fetuses. However, the density of areolae and total number of areolae were greater (P < 0.01) in either small or large MS fetuses compared to WC fetuses illustrating greater histotrophic exchange in MS placentas compared to WC placentas. These results demonstrate altered placental development during late gestation in MS pregnancies corresponding to less sensitive response to intrauterine crowding.