| dc.description.abstract | 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. | en |
