The dietary energy requirements for maintenance of suckling ruminants typically account for more than 75% of the animals total annual energy requirements and are influenced by ani mal size and productive potential. Consequently, it is the maintenance requirement of a ruminant animal in relation to feed intake that will primarily determine the success with which it adapts to its nutritional environment. In the case of the female ruminant, it is energy intake above maintenance that influences her ability to grow and conceive; and to partition nutrients towards the developing conceptus and suckling young. Emerging evidence suggests that the ability of the female ruminant to do the latter may have implications for the lifetime performance and fertility of her offspring. The legacy of undernutrition in utero for the performance of future generations, however, remains to be determined. Within a nutritional environment, factors such as ambience and herbage availability and quality can be manipulated at key stages of the animals reproductive lift: and annual breeding cycle so as to alleviate some of the difficulties of genotype selection. Ways and means by which this can be achieved are discussed. (C) Elsevier/Inra.