Date of Award

12-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Animal and Veterinary Sciences

Committee Member

Dr. Tiffany A. Wilmoth, Committee Chair

Committee Member

Dr. Julia L. Sharp

Committee Member

Dr. Christopher A. Saski

Abstract

Placental efficiency (PE) describes the relationship between placental and fetal weights and is defined as fetal weight divided by placental weight. Within pig litters, PE can vary drastically, resulting in similarly sized pigs associated with very different placenta, up to a 50% weight difference. However, the means enabling the smaller placenta to grow a similarly sized littermate is unknown. The main objectives of this study were to (1) determine the concentration of glucose and cortisol in venous umbilical blood of pigs at birth and evaluate if a relationship existed between concentration and PE, and (2) determine the expression level of genes in placental and associated endometrial tissues of high PE and low PE feto-placental units. For the first objective, terminal Yorkshire crossed pigs (n = 15) were monitored during farrowing to tag umbilical cords and ear notch pigs to ensure feto-placental units were properly matched and PE could be calculated. Neonatal growth measurements were taken to compare high PE and low PE feto-placental units. Umbilical blood samples were taken for quantification of glucose and cortisol. The basis of high PE, a smaller but more efficient placenta, was confirmed as placental weight was reduced, but fetal weight was not different in the high PE group. Given that birth weight, crown-rump length, girth, and body weights up to day 21 did not differ by PE, the survival and postnatal growth performance of pigs grown of high PE placentas should not be reduced. Furthermore, glucose and cortisol concentrations did not differ by PE suggesting high PE placentas have some other means enabling the transport of similar nutrient and hormone quantities despite a reduction in size. For the second objective, maternal line gilts (n = 8) were ovario-hysterectomized on day 95 of gestation to obtain corresponding placental and endometrial samples from each feto-placental unit. PE was calculated to identify the most efficient and least efficient unit in each litter; placental and endometrial samples from these units formed the high PE and low PE comparison groups. RNA sequencing was performed to identify differentially expressed genes (DEG) in high PE compared to low PE placental and endometrial samples. In the placenta, 214 DEG were identified, while zero DEG were identified in the endometrium. Of those DEG in the placenta, 103 were upregulated and 111 were downregulated. Although a portion of the DEG identified in the pig placenta encoded nutrient transporters and gene products with angiogenic or growth factor activity, DEG with alternative functions were also identified, indicating the complexity of the relationship between placental and fetal weights. Overall the results of this study provide new insights into the regulation of PE; however, further research is required to make PE production applicable.

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