Humans are chronically exposed to a mixture of environmental chemicals (ECs), many with metabolic and endocrine disrupting potential, contributing to non-communicable disease burden. Understanding the effects of chronic exposure to low-level mixtures of ECs requires an animal model that reflects real-world conditions, lags behind studies on single ECs. Biosolids, from wastewater treatment, offers a real-life model to investigate the developmental health risks from EC mixtures. Prenatal biosolids exposure studies have documented metabolic perturbations including heavier thyroid glands in male fetuses and reduced bodyweight in prepubertal male lambs followed by catchup growth. We hypothesized that maternal preconceptional and gestational exposure of sheep to biosolids programs sex-specific transcriptional and functional changes in the offspring liver. Ewes (F0) were grazed on either inorganic fertilizer (C) or biosolids-treated pastures (BTP) preconception till parturition. All lambs (n = 15/group with male n= 7/group and females n=8/group) were raised on Control pastures until euthanasia at 9.5 weeks. Next generation sequencing of liver RNA and DESeq2 was used to identify exposure-specific differentially expressed genes (DEG) and sex-differentially expressed genes (SDG). Liver function was assessed with markers of oxidative stress, triglyceride and fibrosis markers. Control lambs exhibited 647 SDGs confirming the inherent sexual dimorphism in hepatic gene expression. A sex-stratified analysis identified 10 DEG, mostly affecting metabolism, in male and none in female lambs. Biosolids exposure diminished the sexual dimorphism in hepatic gene expression barring 41 genes, potentially due to the increase in androgenic steroids found in F0 maternal circulation. Additionally, BTP male lambs showed elevated plasma triglyceride and a trend towards increased liver triglyceride concentrations. The identified effects of prenatal exposure to low-dose mixture of ECs via biosolids, in a precocial species paralleling human developmental patterns holds translational importance for understanding the sexually dimorphic origin of non-communicable diseases.

Female reproductive capacity is shaped by ovarian reserve and patterns of follicle development. Ovarian reserve depletion occurs by follicle activation and atresia, which are affected by environmental chemicals (ECs). Because humans are simultaneously exposed to hundreds of ECs, real-life exposure models are essential to assess patterns of atresia after EC exposure. Previous findings demonstrate maternal preconceptional and gestational EC exposure via biosolids increases activation rate and reduces primordial follicle pool in juvenile, but not adult sheep. We hypothesized that this shift involves changes in death and proliferative pathways that impact follicle atresia from juvenile to adult life. Ovaries were collected from juvenile (9.5 weeks) and adult (2.5 years) offspring from ewes grazed on biosolids-treated pasture (BTP) or inorganic fertilizer-treated pasture (Control). Follicular atresia was assessed through morphological characteristics and molecular death pathways, including expression of markers for apoptosis (CASP3), autophagy (LC3), ferroptosis (GPX4), and proliferation (Ki67). There were higher levels of apoptosis and autophagy, and lower proliferation, in juvenile BTP offspring compared to controls. In adult BTP offspring, apoptosis and proliferation were similar, autophagy was lower, and ferroptosis was higher compared to controls. Apoptosis was lower and ferroptosis was higher in adults than juveniles, regardless of treatment. Adult BTP offspring had lower autophagy and similar proliferation levels than juvenile BTP offspring. These findings suggest that lower autophagy and lack of decrease in proliferation contribute to normalization of activation rate and ovarian pool in BTP adult offspring and supportive of lasting impacts of gestational EC exposure on offspring follicular health.

The decline in human reproductive and metabolic health over the past 50 years is associated with exposure to complex mixtures of anthropogenic time and differs across geographical locations. Health-related issues include declining sperm quality, advanced puberty onset, premature ovarian insufficiency, cancer, obesity, and metabolic syndrome. Prospective animal studies with individual and limited EC mixtures support these observations and provide a means to investigate underlying physiological and molecular mechanisms. The greatest impacts of EC exposure are through programming of the developing embryo and/or fetus, with additional placental effects reported in eutherian mammals. Single-chemical effects and mechanistic studies, including transgenerational epigenetic inheritance, have been undertaken in rodents. Important translational models of human exposure are provided by companion animals, due to a shared environment, and sheep

Developmental exposure to environmental chemicals perturbs establishment and maintenance of the ovarian reserve across the reproductive lifetime, leading to premature follicle depletion and ovarian aging. Considering humans are exposed to a complex mixture of environmental chemicals, real-life models assessing their cumulative impact on the ovarian reserve are needed. Biosolids are a source of a real-life mixture of environmental chemicals. While earlier studies demonstrated that grazing pregnant sheep on biosolids-treated pastures did not influence establishment of the ovarian reserve in fetal life, its impact on subsequent depletion of ovarian reserve during reproductive life of offspring is unknown. We hypothesized that developmental exposure to biosolids accelerates depletion of ovarian reserve. Ovaries were collected from F1 juveniles (9.5 weeks) and adults (2.5 years) born to F0 ewes grazed on control inorganic fertilizer pastures or biosolids-treated pastures from before conception and throughout gestation. The impact on follicular density, activation rate, and anti-Müllerian hormone (mediator of activation) expression by immunohistochemistry was determined. Activation rate was increased in F1 biosolids-treated pastures juveniles with a corresponding reduction in primordial follicle density. In contrast, activation rate and ovarian reserve were similar between control and F1 biosolids-treated pastures adults. The density of anti-Müllerian hormone-positive antral follicles was lower in biosolids-treated pastures juveniles, whereas anti-Müllerian hormone expression tended to be higher in antral follicles of biosolids-treated pastures adults, consistent with the changes in the ovarian reserve. These findings of detrimental effects of developmental exposure to biosolids during juvenile life that normalizes in adults is supportive of a shift in activation rate likely related to peripubertal hormonal changes.

Environmental chemicals (ECs) have been associated with a broad range of disorders and diseases. Daily exposure to various ECs in the environment, or real-life exposure, has raised significant public health concerns. Utilizing the biosolids-treated pasture (BTP) sheep model, this study demonstrates that in-utero exposure to a real-life EC mixture disrupts hypothalamo-pituitary-gonadal (HPG) axis gene expression and reproductive traits in prepubertal (8-week-old, 8w) and adult (11-month-old) male sheep. Ewes were maintained on either BTP or pastures fertilized with inorganic fertilizer [control (C)] from approximately one month prior to insemination until around parturition. Thereafter, all animals were kept under control conditions. Effects on reproductive parameters including testosterone concentrations and the expression of key genes in the HPG axis were evaluated in eight-week-old and adult male offspring from both C and biosolids-exposed (B) groups. Results showed that, at 8w, relative to C (n = 11), B males (n = 11) had lower body weight, and altered testicular expression of HSD3B1, LHR and HSD17B3, BMP4, ABP, P27kip and CELF1. Principal component analysis (PCA) identified two 8w B subgroups, based on hypothalamic expression of GnRH, ESR1, and AR, and pituitary expression of KISSR. The two subgroups also exhibited different serum testosterone concentrations. The largest biosolids effects were observed in the hypothalamus of adult rams with NKB, ESR1, KISS1, AR, DLK1 and GNRH1 mRNA expression differing between B (n = 10) and C (n = 11) rams. Testicular steroidogenic enzymes CYP11A1 and HSD3B1 mRNA expression also differed between exposure groups. PCA identified two adult B subgroups, with BS1 (n = 6) displaying hypothalamic effects and BS2 (n = 4) both hypothalamic and testicular effects. The subgroups also differed in circulating testosterone concentrations. These findings demonstrate that exposure to a real-life EC mixture may predispose some males to infertility, by disrupting key functional HPG markers before puberty with consequent downstream effects on steroid hormones and spermatogenesis.

Identifying associations between phenotype and genotype is the fundamental basis of genetic analyses. Inspired by frequentist probability and the work of R.A. Fisher, genome-wide association studies (GWAS) extract information using averages and variances from genotype-phenotype datasets. Averages and variances are legitimated upon creating distribution density functions obtained through the grouping of data into categories. However, as data from within a given category cannot be differentiated, the investigative power of such methodologies is limited. Genomic Informational Field Theory (GIFT) is a method specifically designed to circumvent this issue. The way GIFT proceeds is opposite to that of GWAS. Whilst GWAS determines the extent to which genes are involved in phenotype formation (bottom-up approach), GIFT determines the degree to which the phenotype can select microstates (genes) for its subsistence (top-down approach). Doing so requires dealing with new genetic concepts, a.k.a. genetic paths, upon which significance levels for genotype-phenotype associations can be determined. By using different datasets obtained in ovis aries related to bone growth (Dataset-1) and to a series of linked metabolic and epigenetic pathways (Dataset-2), we demonstrate that removing the informational barrier linked to categories enhances the investigative and discriminative powers of GIFT, namely that GIFT extracts more information than GWAS. We conclude by suggesting that GIFT is an adequate tool to study how phenotypic plasticity and genetic assimilation are linked.

Abstract Disclosure: Y. Zhou: None. K.M. Halloran: None. M. Bellingham: None. N.P. Evans: None. R.G. Lea: None. K.D. Sinclair: None. V. Padmanabhan: None. The ovarian capacity to provide fertilizable oocytes, regulate folliculogenesis as well as activate and progress primordial follicles into preovulatory follicles are key contributing factors to female fertility and reproductive aging. In sheep, as in humans, while genetics play a role in establishing the ovarian reserve during fetal development, developmental insults such as inappropriate exposure to native steroids or environmental chemicals (ECs) can adversely impact the establishment of the ovarian reserve and, additionally can affect folliculogenesis. Considering humans are exposed to multiple ECs simultaneously which could have additive, synergistic, or antagonistic effects, real-life EC exposure models are needed to assess risks posed by EC exposure. Offspring from sheep grazed on biosolids-treated pasture offers one such real-life exposure model. Studies with day 140 fetuses found maternal exposure to a real-life EC mixture via biosolids increased the proportion of unhealthy transitory follicles (Lea et al., Sci Rep. 2016;6:22279). The present study tested if biosolids exposure during fetal life would impact folliculogenesis, follicle activation and follicle atresia during their adult life. Ovaries were derived from adult EasyCare ewes (age 31.4 ± 0.5 months) whose mothers were grazed on biosolids-treated (BTP, n=10) or inorganic fertilizer-treated (Control, n=10) pastures from preconception through to birth. Ovarian morphometry was undertaken to assess the distribution and health status of follicles. Follicular atresia was evaluated via the expression of Caspase-3, an apoptosis marker. Data analysis utilized Student's t-test for normally distributed variables and Mann-Whitney U tests for non-parametric comparisons. There were no differences in the absolute counts or the percentages of follicle classes at all stages of folliculogenesis, the density of primordial follicles in cortical tissue, or the follicular activation rate. An increase in the percentage of unhealthy activated follicles (post-primordial) was noted in the BTP group (p = 0.014), predominantly in the transitory stage (p = 0.021). Consistent with this, a higher density of Caspase-3 positive primary follicles was observed in the BTP group (p = 0.033). These findings indicate the adverse impacts of fetal exposure to an EC mixture via maternal biosolid exposure on the survival of early-stage activated follicles in adult sheep. The lack of difference in ovarian reserve between the control and BTP groups suggests compensatory mechanisms may be in place to prevent premature depletion of the ovarian reserve. Whether EC mixture exposure via biosolids also has an adverse effect on the quality of the surviving activated follicles remains to be determined. Funding source: NIH R01 ES030374. Presentation: 6/3/2024

Abstract Disclosure: K.M. Halloran: None. J.N. Ciarelli: None. Y. Zhou: None. M. Bellingham: None. R.G. Lea: None. N.P. Evans: None. K.D. Sinclair: None. P. Smith: None. V. Padmanabhan: None. Establishment of the fetal ovarian follicular reserve is a determinant of lifelong fertility. Environmental chemicals (ECs) are implicated in perturbation of early follicle development which may negatively impact adult reproductive function. Considering humans are exposed to a complex cocktail of ECs that may have additive, synergistic and/or antagonistic effects, real-life exposure models are needed to assess the impact of mixtures of ECs on ovarian reserve. Biosolids contain a complex mixture of ECs and earlier studies have shown that grazing pregnant sheep on biosolids-treated pastures (BTP) did not influence the ovarian follicular pool of fetal day 110 lambs. In contrast, an increased proportion of healthy primordial and reduced proportion of healthy transitory follicles, without an impact on their cortical density, was observed in late gestation fetuses (day 140). Collectively this suggests that in BTP sheep, while establishment of an ovarian reserve is not affected its depletion across the reproductive life span may be affected. In this study we tested the hypothesis that prenatal biosolid exposure would affect follicular depletion and negatively impact ovarian reserve in postnatal lambs. Ewes were grazed on pastures treated with either inorganic fertilizer (control; C) or biosolids (BTP) beginning a month before mating and throughout gestation until birth. After birth, ewes and lambs were moved to C pastures. Female lambs (10 C and 11 BTP) were euthanized at 8 weeks of age. Ovarian follicles were classified by stage (primordial, transitory, primary, preantral, and antral) and health status. The impact of exposure to mixture of ECs on follicular cortical density (n/mm2), distribution, health status, and activation rate were assessed. Anti-müllerian hormone (AMH) expression, which correlates with the number of growing follicles, was quantified by immunohistochemical staining. BTP lambs had reduced density (P=0.07) and proportion (P=0.001) of primordial follicles. Activation rate was increased in the BTP group (P=0.01). The density of unhealthy follicles was reduced in the primordial (P=0.04) and transitory (P=0.09) stages, but increased in preantral (P=0.02) and antral (P=0.09) stages. The percentage of unhealthy follicles was reduced in transitory (P=0.09), but increased in preantral (P=0.01) and antral (P=0.07) stages. Consistent with this, increased AMH staining intensity was evident in transitory plus primary follicles (P<0.05). Collectively these results provide evidence that lambs born to BTP ewes have a reduced ovarian follicular pool, increased follicular activation, and increased unhealthy activated follicles at 8 weeks of age. These findings demonstrate the detrimental effects of ECs in biosolids on ovarian health leading to premature depletion of follicular pool and raise concerns regarding the quality of activated follicles. Funding: NIH R01 ES030374 Presentation: 6/1/2024

Abstract Disclosure: S. Thangaraj: None. M. Bellingham: None. R. Lea: None. N. Evans: None. K. Sinclair: None. V. Padmanabhan: None. Humans are chronically exposed to a mixture of environmental chemicals (ECs), many with endocrine disrupting potential, contributing to the development of non-communicable diseases. The adverse health effects of exposure to single ECs have been extensively studied but less is known about the impact of chronic exposure to low levels of a mixture of ECs, which is the real-life exposure scenario. Biosolids, derived from human wastewater treatment, closely reflects the human exposome in both the array and concentration of ECs and is a novel, real-life model to investigate the health risks posed by developmental exposure to mixtures of ECs. Previous studies using the prenatal biosolids exposure model found an increased accumulation of the endocrine disrupting chemical diethylhexylphthalate in the fetal liver and metabolic perturbations including increased thyroid gland weight in the male fetus and reduced bodyweight in prepubertal male lambs. To understand the basis of this sexually dimorphic metabolic phenotype we investigated the transcriptome of liver, the primary metabolic organ, in prepubertal lambs of both sexes. Since many liver genes show sexual dimorphism, with sex-biased genes playing a pivotal role in lipid and drug metabolism, sex-differences in liver gene expression and the impact of prenatal biosolids exposure on it were examined. We hypothesized that maternal preconceptional and gestational exposure of sheep to biosolids programs sex-specific transcriptional changes in the offspring liver. Ewes (F0) were grazed on either inorganic fertilizer (C) or biosolids-treated pastures (BTP) from 1 month before mating till parturition. All lambs (F1) were raised on control pastures after lambing until euthanasia at 8 weeks of age. RNA from liver from Control male (n=7), Control female (n=8), BTP male (n=7) and BTP female (n=8) lambs were subjected to next generation sequencing and differentially expressed genes (DEG) identified with DESeq2 R package. A stratified sex-differential analysis identified 702 DEG between control males and females validating the sexual dimorphism in hepatic gene expression. A sex-stratified analysis between C and BTP identified 5 downregulated DEG - WNT2B, LCN2, TEAD4, QSOX1 and ITIH4 in male and none among female lambs. Biosolids exposure dissipated the sexual dimorphism seen in hepatic gene expression in the controls barring 3 genes involved in cell growth/differentiation (WNT2B) and chromatin regulation (KDM6A, SS18). This may relate to the increase in androgenic steroids found in F0 maternal circulation (Sci Total Environ 2023, 900:165674). The findings of dissipation of the sex-differences in hepatic gene expression by real-life exposure to ECs in a precocial model with a developmental trajectory similar to humans is of translational significance in the context of sexually dimorphic origin of non-communicable diseases.Funding NIH R01ES030374 Presentation: 6/1/2024

Over recent decades, an extensive array of anthropogenic chemicals have entered the environment and have been implicated in the increased incidence of an array of diseases, including metabolic syndrome. The ubiquitous presence of these environmental chemicals (ECs) necessitates the use of real-life exposure models to the assess cumulative risk burden to metabolic health. Sheep that graze on biosolids-treated pastures are exposed to a real-life mixture of ECs such as phthalates, per- and polyfluoroalkyl substances, heavy metals, pharmaceuticals, pesticides, and metabolites thereof, and this EC exposure can result in metabolic disorders in their offspring. Using this model, we evaluated the effects of gestational exposure to a complex EC mixture on plasma triglyceride (TG) concentrations and metabolic and epigenetic regulatory genes in tissues key to energy regulation and storage, including the hypothalamus, liver, and adipose depots of 11-month-old male offspring. Our results demonstrated a binary effect of EC exposure on gene expression particularly in the hypothalamus. Principal component analysis revealed two subsets (B-S1 [n = 6] and B-S2 [n = 4]) within the biosolids group (B, n = 10), relative to the controls (C, n = 11). Changes in body weight, TG levels, and in gene expression in the hypothalamus, and visceral and subcutaneous fat were apparent between biosolid and control and the two subgroups of biosolids animals. These findings demonstrate that gestational exposure to an EC mixture results in differential regulation of metabolic processes in adult male offspring. Binary effects on hypothalamic gene expression and altered expression of lipid metabolism genes in visceral and subcutaneous fat, coupled with phenotypic outcomes, point to differences in individual susceptibility to EC exposure that could predispose vulnerable individuals to later metabolic dysfunction. Developmental exposure to environmental chemical mixture within biosolids affects energy and lipid metabolism in adult male offspring.image

Context. The number of developmentally competent cumulus-oocyte complexes (COCs) retrieved during Ovum Pick-Up (OPU) determines success in both bovine and human assisted reproduction. Follicular flushing for COC retrieval is practicsed widely in humans but not in cattle. Aims. To determine the benefits of follicular flushing in cattle and assess the merits of a novel 16G double-lumen needle ('OxIVF') that flushes laterally to the needle shaft. Methods. Experiment 1 flushed 655 antral follicles (>= 7 mm) from 255 abattoir-derived cattle ovaries. In Experiment 2, 12 Holstein heifers underwent two cycles of OPU in a cross-over design comparing both needle types. In Experiment 3, 11 Holstein heifers underwent two cycles of OPU using the OxIVF needle in a cross-over design: flushing (>= 7 mm follicles) vs a 'Hybrid' approach of flushing (>= 7 mm follicles) and aspiration (5-7 mm follicles); followed by two cycles of standard follicle aspiration (>5 mm follicles). Key results. In Experiment 1, COC recovery was greater (P = 0.034) for the OxIVF vs Standard needle (mean +/- s.e.; 74.1 +/- 2.10% vs 67.0 +/- 2.23%); yield of Grade 1 COCs was also greater (20.1 +/- 1.97% vs 8.2 +/- 1.38%; P < 0.001). In Experiment 2, recovery of COCs was greater (P = 0.045) for the OxIVF vs Standard needle (89.1 +/- 2.98% vs 79.6 +/- 3.47%). Day 6 embryo yield was also greater (P = 0.017) for the OxIVF vs Standard needle (87.2 +/- 4.38% vs 67.6 +/- 6.73%). In Experiment 3, recovery of COCs was greater (P = 0.033) for 'Flush' vs 'Aspirate' groups (82.1 +/- 5.06% vs 66.2 +/- 3.48%). However, number of Day 8 blastocysts for the 'Hybrid' vs 'Flush' approach (9.2 +/- 1.39 vs 6.5 +/- 1.05 per cycle) did not reach statistical significance. Conclusions. Follicular flushing using the OxIVF needle, embracing the 'Hybrid' approach, has the potential to increase oocyte retrieval and blastocyst number per donor cycle in cattle but requires further validation. Implications. Larger scale studies will seek to confirm benefits of follicular flushing using the OxIVF needle in cattle. Future studies should consider applications in both equine and human assisted reproduction.

INTRODUCTION:Maternal lifestyle behaviors can affect blood pressure with consequences for maternal and offspring health. The aim of this study was to investigate the effectiveness of the Smarter Pregnancy digital lifestyle coaching program on maternal blood pressure during the first trimester. METHODS:The study was conducted on data of the Rotterdam Periconception Cohort from 2010 to 2019, and analysis was completed in 2024. The intervention group included 132 pregnant women using Smarter Pregnancy for 6-24 weeks within 30 months before the study entry. The control group included 1,091 pregnant women who did not use Smarter Pregnancy. Outcomes included changes in systolic, diastolic, and mean arterial blood pressures between baseline and first trimester. Lifestyle behaviors were tracked in the intervention group at 12 and 24 weeks of the program, using lifestyle risk score for vegetables, fruits, smoking, and alcohol. RESULTS:Using multivariable analysis, the intervention group showed reductions in systolic (βadj= -2.34 mmHg, 95% CI= -4.67, -0.01), diastolic (βadj= -2.00 mmHg, 95% CI= -3.57, -0.45), and mean arterial (βadj= -2.22 mmHg, 95% CI= -3.81, -0.52) blood pressures compared with the control group. When stratifying for conception mode, reductions were observed in diastolic (βadj= -2.38, 95% CI= -4.20, -0.56) and mean arterial (βadj= -2.63, 95% CI= -4.61, -0.56) blood pressures only in women who underwent assisted reproduction (n=91). Smarter Pregnancy use was associated with a reduction in lifestyle risk score, indicating improved lifestyle behaviors, after 12 (β= -0.84, 95% CI= -1.19, -0.49) and 24 (β= -1.07, 95% CI= -1.44, -0.69) weeks. The lifestyle risk score was also significantly reduced in assisted reproduction and natural pregnancy subgroups. CONCLUSIONS:The use of Smarter Pregnancy is associated with consistent but small reductions in maternal blood pressure during the first trimester, supporting further implementation in health care.

The required intake of macronutrients by women during the periconceptional period for optimal fetal growth is the subject of ongoing investigation. Intake of polyunsaturated fatty acids (PUFA) is positively associated with fetal neural development, growth velocity and birth weight. However, limited evidence indicates that PUFAs play a role in embryogenesis. We aim to investigate the associations between maternal PUFA dietary intake and first trimester embryonic volume (EV) and head volume (HV). In a prospective cohort study (2013-2020), 464 pregnant women at < 8 weeks of gestation were included. Maternal dietary intake of PUFAs, including omega 3 (docosahexaenoic acid, DHA and eicosapentaeonic acid, EPA) and 6, was obtained from food frequency questionnaires, and first trimester three-dimensional ultrasound examinations were performed to measure EV and HV using Virtual Reality techniques. More than 70% of the population had omega 3 intakes below recommendations. A higher intake of PUFAs was associated with a smaller embryonic HV/EV ratio after adjusting for confounders (EPA p = 0.012, DHA p = 0.015, omega 3 and 6 p < 0.001), but no associations were found with EV or HV alone. Omega 3 from fish oil supplements alone was not associated with embryonic growth. Strong adherence to a PUFA-rich dietary pattern was associated with a smaller embryonic HV/EV ratio (DHA and EPA-rich diet p = 0.054, PUFA-rich diet p = 0.002). It is important to increase awareness of the high prevalence of omega 3-deficiency among pregnant women, and the opportunity for prevention by increasing PUFA intake, thereby reducing the risks of adverse pregnancy outcomes which originate during the periconceptional period.

The developmental integrity and well-being of offspring are influenced by events that occur in utero, particularly around the time of conception. Although extraneous factors, such as environmental temperature and exposure to environmental chemicals, can each have a bearing on these events, the epigenetic mechanisms that direct cellular differentiation during early development in ruminants are best described for studies that have investigated the effects of parental nutrition or pregnancy outcomes following assisted reproduction. In this article, the case is made that the genetic constitution of an individual directs epigenetic responses to environmental stimuli, and consideration in this regard is also given to the origins of sexual dimorphism and mechanisms of germline intergenerational inheritance. These aspects are considered in the context of epigenetic modifications that take place during the normal course of gametogenesis and embryogenesis, and again following either dietary or procedural interventions such as embryo culture. A recurring feature of such interventions, irrespective of species, is that one carbon metabolic pathways are invariably disrupted, and this affects the provision of methyl groups for chromatin and RNA methylation. Interspecific variation in how these pathways operate, both within the liver and in germ cells, indicates that ruminants may be particularly sensitive in this regard. Recent advances in genomic technologies should enable rapid progress in these areas. Knowledge gained can be integrated into breed improvement programs and used to tailor management practices to specific breeds and strains (including sexes) within breeds. Ultimately, consideration should be given to integrating metagenomics into analyses of genetic-directed epigenetic programming of animal development.

Exposure to environmental chemicals during fetal and pre-pubertal development has been associated with perturbed mammalian reproductive development and function. Indeed, there is increasing evidence that chemical contaminants adversely impact the developing fetus in utero, the pre-pubertal infant and the adult. In the male, chemical exposures have been associated with sub-fertility, malformations at birth and testicular cancer and in the female, with precocious puberty, premature menopause and polycystic ovarian disease. Although temporal changes and geographical differences in human reproductive function are indicative of an environmental aetiology, determining underlying mechanisms and true cause and effect is problematic. Developmental and functional impacts of individual or chemical mixtures are explored using three animal models. (1) Pregnant ewes exposed to chemical mixtures in widely used sewage sludge derived fertiliser (biosolids) provide a model of real-life human exposure. (2) Companion dogs that share our homes serve as a sentinel species for human exposure to household pollutants. (3) Neonatal mouse gonads exposed in vitro to selected chemicals provide information on subtle perturbations of early gonadal development. (1: sheep) Exposure induced changes in the transcriptome (testis and ovary) are reported combined with altered fetal gonadal morphology and endocrine function. (2: dog) a decline in dog semen quality over 26 years parallels that reported in the human. Regional differences in chemical profiles and morphology also approximate those reported in the human. Specific chemical contaminants alter semen function at environmental/tissue concentrations. (3: mouse) gonadal concentrations of chemicals alter follicle development in the early post-natal ovary and perturb cellular development in the testis. Details on each of these paradigms will be presented. This combination of animal models has provided key insights into possible chemical perturbations of human fertility and reproductive health.