International Symposium on Ruminant Physiology: Developmental epigenetics-Understanding genetic and sexually dimorphic responses to parental diet and outcomes following assisted reproduction.

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.