Epigenetic Programming of Physiological Functions by a Prenatal Stressor and Genetic Parameters of Temperament in Cattle

This project consisted of two main objectives. Objective 1 assessed the influences of prenatal stress on 1) postnatal physiological functions and 2) the postnatal presence and prevalence of epigenetic differences, specifically degree of DNA methylation, in immune cells of calves. Objective 2 assessed the genetic parameters of temperament across an age continuum in cattle. Calves studied in Objective 1 were progeny from Brahman cows that were either transported at 60, 80, 100, 120, and 140 ± 5 d of gestation (the prenatally stressed group, PNS) or were designated as the nontransported Control group. After weaning, response to an endotoxin challenge was assessed in 16 PNS and 16 Control bull calves. In response to LPS, PNS bull calves exhibited increased rectal temperatures, IFN-γ, and TNF-α, as well as decreased serum IL-6. Additionally, a subset of bull calves (n=7 PNS; n= 7 Control) was selected from the total population for evaluation of genome-wide DNA methylation in white blood cells. There were 16,128 CpG sites, 226 CHG sites, and 391 CHH sites differentially methylated in PNS compared to Control calves. An enrichment analysis was used to associate differentially methylated sites in PNS calves with predicted alterations to biological pathways. Enrichment analysis revealed alterations to biological pathways related to functions such as immune function, HPA axis activity, and neurotransmitter signaling. Objective 2 sought to further understand the genetic components of temperament. Random regression procedures estimated genetic parameters of temperament across an age continuum in a population of commercial beef cattle. As the cattle matured over time there was an increased influence of permanent environmental effects and a decreased influence of additive genetic effects based on random regression analyses