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

Endogenous Cortisol, Luteinizing Hormone, and Testosterone Secretion and GnRH-induced Luteinizing Hormone and Testosterone Secretion in Prenatally Stressed Sexually Mature Brahman Bulls

The purpose of this experiment was to determine the effects of prenatal transportation stress (PNS) on LH, testosterone, and cortisol secretion before and after GnRH stimulation in sexually mature Brahman bulls. Forty-eight Brahman cows were exposed to a transportation event at 5 stages of gestation (and 48 cows were non-transported controls). Bulls from these cows were electroejaculated every 2 wk beginning at a scrotal circumference of 24 cm through sexual maturity (i.e., 500 million sperm/ejaculate). The initial 11 control and 12 PNS bulls to reach sexual maturity were selected for endocrine evaluation. Within 7-21 d after reaching sexual maturity, bulls were fitted with jugular cannulas, and blood samples were collected at 15-min intervals for 6 h. Exogenous GnRH was then administered intravenously (10 ng/kg BW) and blood collection continued at 15-min intervals for an additional 8 h. Concentrations of LH, testosterone, and cortisol in serum were determined. Amplitude and maximum concentration of a detectable LH pulse and testosterone response, baseline concentration, average concentration in the h prior to GnRH administration, and area under the curve were calculated for LH and testosterone in the 4-h period immediately preceding and 6-h period immediately following GnRH administration. Cortisol in the h prior to GnRH administration and area under the curve were calculated for the 4-h period immediately preceding GnRH administration. Duration of the GnRH-induced LH release was determined. More PNS (10 of 11) than control (3 of 12) bulls exhibited an LH pulse prior to GnRH administration (P0.1). Bulls responded similarly to exogenous GnRH, except duration of GnRH-induced LH release which was greater (P=0.02) in PNS (268±18 min) relative to control (207±16 min) bulls. Prenatal stress affected postnatal secretion of LH, testosterone, and cortisol in sexually mature Brahman bulls

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