423 Impact of sire overnutrition on preimplantation conceptus transcriptome profile in the bovine.

Abstract Bull overnutrition has been shown to negatively impact semen quality and early embryonic development; however, the contributions of paternal overnutrition on pre-implantation conceptus development remain unknown in the bovine. The aim of this study was to investigate the impact of paternal overnutrition on the transcriptome of d 15 preimplantation conceptus. We hypothesized that paternal overnutrition would negatively impact preimplantation conceptus development, leading to changes in the abundance of transcripts associated with conceptus developmental competency. Twenty-nine Angus bulls (age = 359.4 ± 3.7 d; BW = 447.28 ± 51.76 kg) were randomly assigned one of two dietary treatments for 114 days: 1) Moderate Gain (MG): diet formulated to promote an average daily gain of 1.22 kg/d, or 2) High Gain (HG): diet formulated to promote an average daily gain of 1.81 kg/d. After the feeding period, semen was collected by electroejaculation, cryopreserved, and used for in vitro embryo production. Nonlactating beef cows were synchronized using an industry-standard estrus synchronization protocol and randomly assigned to receive two embryos from the same sire. Uterine flushes were performed 8 d after embryo transfer (d 15 after estrus), and conceptuses from HG (n = 4 flushes) and MG (n = 4 flushes) bulls were collected for transcriptome analyses by RNA sequencing. Differentially expressed gene (DEG) analysis was performed using the DESeq2 R package with false discovery rate (FDR) adjustment. A total of 15 DEGs (FDR < 0.1; 8 downregulated; 7 upregulated) in HG conceptuses. A total of 387 DEGs (141 downregulated; 246 upregulated) were identified when using a threshold of P-value ≤ 0.05 and a -log2 fold change ≤ -1 or ≥ 1. GO enrichment analysis of the 387 DEG identified 121 biological processes, and 22 cellular components associated with HG (P < 0.05). Canonical pathway analysis of 371 DEGs mapped by IPA identified 61 significant pathways (P < 0.05), primarily related to growth factor signaling, protein modification, ion transport, lipid metabolism, and cellular signaling. Our results suggest that paternal overnutrition resulted in subtle changes to the transcriptome of d 15 preimplantation bovine conceptuses. Further research is required to determine the contribution of these subtle transcriptome differences to conceptus development and pregnancy establishment.