121. Dietary Fatty Acid Profile and Choline Altered the Transcriptome of Placental Tissue in Beef Cows

Abstract Lipids in the uterine luminal fluid are required to support conceptus elongation. The elongating conceptus is capable of increasing more than 1000-fold in size during the peri-implantation phase and utilizes lipids as an efficient fuel source. The elongated conceptus will then begin shallow implantation into the endometrial luminal epithelium, initiating placentation. Post-implantation, placentomes become the only site of nutrient exchange between maternal and fetal circulation. Therefore, our objective was to provide a dietary supplementation strategy containing rumen-inert mono- and polyunsaturated fatty acids and rumen-protected choline to support conceptus elongation and placenta formation during early pregnancy and characterize the gene expression in cotyledons at parturition. One hundred suckled multiparous Angus cows were randomly assigned on d -30 to receive either TARG) 100 g of a rumen-inert mono- and polyunsaturated fatty acid source (Essentiom; Church and Dwight Co., Inc., Princeton, NJ) plus 60 g of a rumen-protected choline source (ReaShure; Balchem, Montvale, NJ) or CON) 114 g of a saturated fatty acid source (Energy Booster 100; Milk Specialties, Eden Prairie, MN). Treatments were top-dressed daily into a similar total mixed ration until d 30. All cows were synchronized using a 7-day CO-synch+CIDR protocol and received timed artificial insemination by the same technician on d 0. At calving, cotyledon tissue was collected (CON = 10 and TARG = 8) for RNAseq analysis. The effects of treatment and sex (M) were analyzed using ANOVA in RStudio. The average gestation length for CON was 275.5 ± 3.4 days, and TARG was 275.6 ± 2.9 days (P = 0.93). The average gestation length for male calves in CON was 275 ± 3.67 days, and for male calves in TARG 276.2 ± 3.56 days (P = 0.61). To identify differentially expressed genes (DEG), DESeq2 v. 1.42.1 was used, and pairwise comparison was performed between the TARG and CON treatment groups and within sex (TARG Male vs. CON Male). Between CON and TARG treatments, there were 157 DEGs (P-value £ 0.05 and log2FC |1|) with 40 upregulated and 117 downregulated in TARG in pathways involved in modulating inflammatory responses. Between CON and TARG treatments in males only, there were 621 DEGs (P-value £ 0.05 and log2FC |1|) with 270 upregulated and 351 downregulated in TARG, involved in mitochondrial and immune pathways. Collectively, dietary supplementation of beef cows during early gestation modulated the gene expression in the cotyledon collected from placentas at parturition.