BioProject

We measured the gene expression profile of fetal liver to identify differentially expressed genes (DEG), biological processes (BP), and pathways underlying hepatic function and development in response to vitamin and mineral supplementation (VTM or NoVTM – at least 71 days pre-breeding to day 83 of gestation) and rate of weight gain (low [LG] or moderate [MG] – from breeding to day 83). The treatments were arranged as follows: (1) no vitamin and mineral supplementation and low gain (NoVTM_LG, n = 8); (2) vitamin and mineral supplementation and low gain (VTM_LG, n = 8); (3) no vitamin and mineral supplementation and moderate gain (NoVTM_MG, n = 8), and (4) vitamin and mineral supplementation and moderate gain (VTM_MG, n = 7). Crossbred Angus beef heifers (n = 35) were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial design. Fetal liver was collected on day 83 ± 0.27 of gestation snap-frozen, and stored at −80 °C. After RNA quality control, read mapping was performed with STAR aligner to the bovine ARS-UCD1.2 reference genome. Strand-specific RNA libraries were prepared using the NEBNext® Ultra™ II Directional RNA Library Prep Kit for Illumina (New England BioLabs®, Ipswich, MA, USA). Total RNA was extracted and libraries were sequenced on the Illumina® NovaSeq 6000 platform. After RNA quality control, read mapping was performed with STAR aligner to the bovine ARS-UCD1.2 reference genome. After quality control, differential gene expression analysis was carried out using edgeR. Differentially expressed genes (DEGs) were identified after multiple testing correction of the p-values based on the Benjamini-Hochberg methodology (FDR < 0.1). Our results show that vitamin and mineral supplementation and the rate of weight gain led to differential expression of hepatic genes in all treatments. We identified 591 unique differentially expressed genes across all six VTM-gain contrasts (FDR < 0.1). Over-represented pathways were related to energy metabolism, including PPAR and PI3K-Akt signaling pathways, as well as lipid metabolism, mineral transport, and amino acid transport. Our findings suggest that periconceptual maternal nutrition affects fetal hepatic function through altered expression of energy and lipid-related genes. Overall design: Angus-cross heifers (n = 35) were randomly assigned by initial body weight (average = 359.5 ± 7.1 kg) to a 2×2 factorial arrangement of treatments. The factors examined included vitamin and mineral supplementation (VTM or NoVTM) and rate of gain (low gain – LG or moderate gain – MG). The treatments were arranged as follows: (1) no vitamin and mineral supplementation and low gain (NoVTM_LG, n = 8); (2) vitamin and mineral supplementation and low gain (VTM_LG, n = 8); (3) no vitamin and mineral supplementation and moderate gain (NoVTM_MG, n = 8), and (4) vitamin and mineral supplementation and moderate gain (VTM_MG, n = 7). Diets were delivered once daily via total mixed ration and consisted of triticale hay, corn silage, modified distillers grains plus solubles, ground corn, and if indicated by treatment, mineral premix. To achieve MG (0.79 kg/d), heifers were fed the total mixed ration with the addition of the starch-based protein/energy supplement (a blend of ground corn, dried distillers grains plus solubles, wheat midds, fish oil, urea, and ethoxyquin). The LG heifers were maintained on the basal total mixed ration and targeted to gain 0.28 kg/d. The VTM treatment started 71 to 148 days before artificial insemination by providing 0.45 kg/heifer daily of a ground corn and vitamin and mineral premix (Purina Wind & Rain Storm All-Season 7.5 Complete, Land O’Lakes, Inc., Arden Hills, MN). Based on the VTM starting date, heifers were assigned to one of seven breeding groups so that the supplementation period was at least 60 days for all. At breeding, heifers were randomly assigned to either LG or MG treatments within their respective VTM treatment. Heifers were bred by artificial insemination using female-sexed semen from a single sire. The VTM and rate of gain treatments were carried out until day 83 ± 0.27 of gestation, when fetal tissues were collected. After QC, 31 samples (seven or eight samples per group) remained for further analyses. Differential gene expression analysis was carried out using edgeR. To make all pair-wise comparisons between the four treatment groups, six contrasts were created as follows: (1) VTM_MG vs. NoVTM_LG, (2) VTM_MG vs. VTM_LG, (3) VTM_MG vs. NoVTM_MG, (4) VTM_LG vs. NoVTM_LG, (5) VTM_LG vs. NoVTM_MG, (6) NoVTM_MG vs. NoVTM_LG. Multiple testing adjustment of the p-values (padj) was adopted using the Benjamini–Hochberg procedure for false discovery rate (FDR).