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

Exploring How Maternal Phosphorus Status Affects Calf Growth and Performance

Phosphorus is an important component of bodily functions and is critical for adequate growth and development. This experiment evaluated the effect of maternal phosphorus intake on the growth and health of the calves. Treatments were 1) a free-choice mineral containing no supplemental P or 2) a free-choice mineral with 4% supplemental phosphorus. Primiparous, or pregnant for the first time, crossbred Angus beef cows (n = 36) were stratified by body weight and pregnancy status (bred by artificial insemination or natural service) then assigned to pasture groups (4 groups, 2/treatment, 9 heifers/group). These bred heifers had been receiving these same dietary treatments from 30 days after weaning until confirmation of pregnancy. Eighteen bred heifers from each treatment were selected randomly to continue into this experiment. At calving, colostrum and blood samples were collected from a subset of 12 heifers/treatment (6/group). Body weights were obtained for all cattle. Data were analyzed using the MIXED procedure of SAS. Cows grazed mixed grass pastures; monthly forage samples ranged from 0.28% to 0.36% P. There were no differences (P \u3e 0.10) for cow body weight during gestation, calf birth weight, or calf weight at an average age of 21 days. There were also no differences (P \u3e 0.10) in colostrum components (fat, protein, lactose, and IgG) or in the serum IgG or plasma mineral concentrations for both cows and calves 48 hours after birth. All calves were sampled at approximately 21 days of age, and there were no treatment differences (P \u3e 0.10) in serum IgG concentrations. There were no benefits to supplementing gestating heifers with phosphorus when they grazed pasture with a history of fertilization with livestock manure

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

Genome-wide DNA methylation alteration in prenatally stressed Brahman heifer calves with the advancement of age

Possible phenotypic impairments associated with maternal stress during gestation in beef cattle may be explained by epigenetic effects. This study examined the impact of prenatal transportation stress on DNA methylation of lymphocytes of Brahman cows over the first 5 years of life. Methylation analysis through reduced representation bisulphite sequencing was conducted on DNA from lymphocytes from 28 paired samples from 6 prenatally stressed (PNS) and 8 control (Control) females obtained initially when they were 28 days of age and 5 years of age. There were 14,386 CpG (C = cytosine; p = phosphate; G = guanine) sites differentially methylated (P < 0.01) in 5-yr-old Control cows compared to their lymphocyte DNA at 28 days of age, this number was slightly decreased in 5-yr-old PNS with 13,378 CpG sites. Only 2,749 age-related differentially methylated CpG sites were seen within PNS females. There were 2,637 CpG sites differentially methylated (P < 0.01) in PNS cows relative to Controls at 5 years of age. There were differentially methylated genes in 5-yr-old cows that contributed similarly to altered gene pathways in both treatment groups. Canonical pathways altered in PNS compared to Control cows at 5 years of age were mostly related to development and growth, nervous system development and function, and immune response. Prenatal stress appeared to alter the epigenome in Brahman cows compared to Control at 5 years of age, which implies a persistent intervention in DNA methylation in lymphocytes, and may confer long-lasting effects on gene expression, and consequently relevant phenotypic changes

Inter-Individual Variation in DNA Methylation Patterns across Two Tissues and Leukocytes in Mature Brahman Cattle

Quantifying the natural inter-individual variation in DNA methylation patterns is important for identifying its contribution to phenotypic variation, but also for understanding how the environment affects variability, and for incorporation into statistical analyses. The inter-individual variation in DNA methylation patterns in female cattle and the effect that a prenatal stressor has on such variability have yet to be quantified. Thus, the objective of this study was to utilize methylation data from mature Brahman females to quantify the inter-individual variation in DNA methylation. Pregnant Brahman cows were transported for 2 h durations at days 60 ± 5; 80 ± 5; 100 ± 5; 120 ± 5; and 140 ± 5 of gestation. A non-transport group was maintained as a control. Leukocytes, amygdala, and anterior pituitary glands were harvested from eight cows born from the non-transport group (Control) and six from the transport group (PNS) at 5 years of age. The DNA harvested from the anterior pituitary contained the greatest variability in DNA methylation of cytosine-phosphate-guanine (mCpG) sites from both the PNS and Control groups, and the amygdala had the least. Numerous variable mCpG sites were associated with retrotransposable elements and highly repetitive regions of the genome. Some of the genomic features that had high variation in DNA methylation are involved in immune responses, signaling, responses to stimuli, and metabolic processes. The small overlap of highly variable CpG sites and features between tissues and leukocytes supports the role of variable DNA methylation in regulating tissue-specific gene expression. Many of the CpG sites that exhibited high variability in DNA methylation were common between the PNS and Control groups within a tissue, but there was little overlap in genomic features with high variability. The interaction between the prenatal environment and the genome could be responsible for the differences in location of the variable DNA methylation