Feed and forage toxicants affecting embryo survival and fetal development

Early embryonic and fetal development in mammals is sensitive to deficienci es and excesses of specific nutrients and toxicants. Operating directly and /or indirectly, these deficiencies and excesses can result in embryonic dea th or, in less severe circumstances, disruption of normal embryo and fetal growth. This paper explores the threats posed by feed and forage toxicants to the developing embryo and their impact on early programming of fetal dev elopment. Using significant examples, we consider the relevance of temporal sensitivities during early development in utero, and their implications fo r the morphology and functional competence of specific organs and tissues. (C) 2000 by Elsevier Science inc.