Nutritional Epigenetic Modifications in Beef Cattle
Creators: Gibril, Mumuni
Publisher: name: University of Alberta Library
Year: 2023

<p>Nutrition of the beef cow during pregnancy influences fetal development and potential changes in phenotype. On average 9-10% of beef cows are below the optimal condition score of 2.5/5 at both pre-breeding and pregnancy tests, indicating potential nutritional stress during gestation (Waldner and García Guerra, 2013). Epigenetic modifications are reported to regulate the changes in phenotype due to maternal nutrition during gestation. Prior research on the impact of gestational feed restriction during early to mid-gestation on semen methylation, reproductive development, and carcass characteristics in cattle progeny revealed differentially methylated regions (DMRs) in the semen as well as influences on growth trends and carcass characteristics in bull and steer progeny. The objective of the current study is to evaluate further the influence of maternal nutrition during gestation on molecular mechanisms regulating the observed changes in semen, Longissimus dorsi (LD), Semimembranosus muscle (SM), and liver (LV) at slaughter in cattle progeny (steers and bulls) and validate the DMRs identified in the semen methylation analysis. <br>
DNA and RNA were extracted from the progeny and categorized based on the diet provided to their respective dams (Moderate or low diet) during gestation and genetic potential for residual feed intake (High-RFI or Low-RFI). DNA methylation analysis was conducted in LD, SM, and LV in steers and semen in bull progeny using EpiTYPER technology to validate DMRs identified in semen WGBS analysis and assess the influence of prenatal nutrition and RFI on the methylation at slaughter. The influence of prenatal nutrition and/or RFI on gene expression was also conducted in LD, SM, LV, and testis in the progeny at slaughter using nCounter element Tagset carried out by NanoString technologies.<br>
In the bull study, the DMR validation study showed a difference in the methylation trend between average methylation (EpiTYPER) and mean methylation difference (whole-genome bisulfite sequencing [WGBS]). However, semen CpG methylation analysis showed that prenatal diet increased methylation in moderate diet (Mdiet) progeny in DMRs associated with testicular development and reproductive development (ALDH3B1 and INSL3) as well as genomic imprinting and growth development (IGF2R-DMR2 and GRB10). Additionally, Low diet (Ldiet) bulls displayed higher expressions of the growth-promoting gene PDPK1 in LD and SM muscle. <br>
In steers, DMR methylation due to prenatal nutrition in LD, SM, and LV tissues mostly did not corroborate the findings in semen WGBS analysis. However, DMRs, INSL3, and IGF2R showed similar methylation trends in semen and SM due to prenatal nutrition while GRB10 displayed similar methylation trends in SM and LV tissues in the current study. Also, RFI had a greater influence on methylation in LD, SM, and LV tissues while prenatal nutrition had a higher influence on methylation in SM muscle compared to LD and LV. The findings from this project show potential molecular modifications as a result of prenatal nutrition and selection for feed efficiency and provide a further understanding of epigenetic mechanisms regulating fetal programming phenomenon. </p>