PS1-12. Influence of Early Gestational Maternal Mineral Supplementation on Mirna-Mediated Gene Expression in Fetal Liver of Beef Cattle.

Abstract Maternal nutrition plays a central role in supplying the nutrients required for fetal development throughout gestation. The maternal environment can have long-term effects on offspring programming via epigenetic regulation. However, how maternal nutrition influences fetal epigenetic programming during early pregnancy remains under investigated. Therefore, the objective of this study was to investigate how maternal vitamin and mineral supplementation from the pre-breeding period through day 83 of gestation affects hepatic miRNA expression, regulation of target genes, and underlying metabolic processes. Crossbred Angus heifers (n = 16) were divided into supplemented (VTM, n = 8) and non-supplemented (NoVTM, n = 8) groups from day 71 before breeding until day 83 of gestation. Both groups received a daily total mixed ration, with the VTM group receiving 113g/heifer daily of a vitamin and mineral premix (Purina Wind and Rain Storm All-Season 7.5 Complete). The heifers were artificially inseminated (AI) with female sexed semen from a single sire, and pregnancy was confirmed at day 35 post-AI, with fetal sexing performed at day 60 using transrectal ultrasonography. On day 83, fetuses were harvested and total RNA isolated from the liver for small non-coding RNA (sncRNA) sequencing. Reads were mapped to the bovine reference genome using Bowtie for hierarchical annotation of major sncRNA classes, including miRNAs, tRNAderived fragments, and piRNAs. Differential expression analysis was performed in R using the DESeq2 package. We identified 11 piRNAs and one tRNA that were differentially expressed, along with 20 differentially expressed miRNAs. In total, 12 miRNAs were upregulated (miR-2285bk, miR-20b, miR-194b, miR-148b, miR-146a, miR-1388-5p, miR-126-3p, miR-11989, miR-11988, miR-11987, miR-101 and miR-378c) and 8 were downregulated (miR-199a-5p, miR-99a-5p, miR-499, miR-377, miR-28, miR-24-3p, miR-1296 and miR-340) in the VTM group. Functional enrichment analysis (KEGG pathways and Gene Ontology terms) of predicted target genes was carried out using the clusterProfiler R package. The miRNA-target genes were underlying pathways associated with receptor-mediated signaling, transcriptional regulation, and developmental processes (FDR < 0.05), including genes such as ISL2, NRP1, NRP2, and NTRK3. These findings suggest that maternal vitamin and mineral supplementation may influence target genes through miRNA-mediated modulation of key signaling and developmental pathways. Further studies are needed to evaluate the long-term outcomes of these transcriptional changes on herd performance.