PS5-18. Impact of Hypo- or Hyper-methylating Diets During Early Placental Establishment on Fetal and Placental Development at 46- and 107- days Gestation

Abstract Seasonal effects on pregnancy loss are thought to involve DNA methylation of placental tissue. We previously showed placentas had increased 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) with a reduced ratio (5mC:5hmC) in winter compared to summer. The objective of the current study was to determine how diet during early pregnancy alters methylation status and placental histomorphology in summer (SUM) and winter (WIN). Cyclic gilts were artificially inseminated using single-sire semen then randomly assigned to one of three diets fed from day 5 through 30 post-breeding; 1.) Control gestation diet (11.7% CP, CON), 2.) Control diet + phytogenic blend (HYPO), or 3.) Control diet + methionine (HYPER). All gilts were fed CON diet from day 31 post-breeding until harvest at mid- (d46 ± 1.5d) or late- gestation (d107 ± 0.93d) when the reproductive tract was removed and the uterus was opened along the antimesometrial surface. Fetal sex and location within uterus were recorded. Ovulation rate, number of viable fetuses, dead fetuses, mummies, individual fetal and placental weights, umbilical lengths, and uterine length and weight were recorded. Data were analyzed using Mixed procedure (SAS) for each day (46 or 107) with diet, season, week bred as fixed effects; gestation day, total fetuses, dam age as covariates; and sire(supplier) random effect. If there was no interaction, only main effects were tested. Trait LSMeans (SE) are presented in Table 1. At d46, male ratio tended (P 0.10) to be fewest in CON, intermediate in HYPO, and greatest in HYPER. Fetal loss at d46 tended (P 0.10) to be greater in WIN versus SUM. A diet by season effect at d46 tended (P 0.10) to influence average placental weight with CON/SUM less than CON/WIN, HYPER/WIN, and HYPO/SUM with HYPER/SUM and HYPO/WIN intermediate. Several traits were affected by the interaction of diet by season at d107 gestation (Table 1). The averages for full uterine weight, empty uterine weight, and estimated gravid fluid were similar between CON WIN and HYPER SUM but both differed (P 0.05) from CON SUM and HYPO SUM. Both average fetal weight and placental weight were less (P 0.05) from HYPER SUM dams and greatest (P 0.05) from CON SUM dams. Placental efficiency was greatest (P 0.05) from HYPER dams in comparison to CON and HYPO dams. Supplementing gestation diets with hypo- or hyper-methylating components in early gestation during placental establishment impacted uterine, placental, and fetal traits more during late gestation. Fetal and litter traits from control diets during winter were similar to hypermethylated diets during summer. Feeding hypomethylated diets during early pregnancy in summer had similar fetal and litter traits to control diets during summer. USDA is an equal opportunity provider and employer.