Ruminant Nutrition Symposium: Optimizing Performance of the Offspring: nourishing and managing the dam and postnatal calf for optimal lactation, reproduction, and immunity.

For several mammalian species, it has been shown that fetal and early postnatal nutrition has a role in long-term lipid and glucose metabolism of the offspring, and it thus also may have consequences on milk yield in the dairy cow. For instance, high-energy diets during the last weeks of pregnancy may result in increased glycemia, which in turn, may alter fetal adipose tissue development. However, most research efforts on management and nutrition of dry cows have focused on minimizing metabolic disorders of the postpartum cow without devoting much attention to potential consequences for the offspring. Similarly, nutritional needs for proper placental development and early fetal growth have received little attention, despite the fact that alterations in placental and fetal development may alter expression of genes participating in homeorhesis of the offspring. Therefore, nutrition of the pregnant cow, both while lactating and dry, should also consider aspects of placental and fetal development that may affect health and performance of the progeny. Similarly, newborn calves and young heifers are fed to ensure a particular growth target without compromising mammary development, although data linking postnatal growth targets with future milk yield are scarce. However, milk yield not only depends on mammary development, but also on nutrient partitioning, which is regulated by the endocrine milieu. There are some periods of time during development where nutrition may have long-lasting effects on metabolic function and milk production. For instance, the first months of postnatal life seem to be critical because recent data from both retrospective and controlled studies indicate that increased growth rate or plane of nutrition during this phase is positively associated with future milk production. Postnatal growth rate depends on nutrition (a necessary but not sufficient condition) and management (i.e., grouping strategies and housing systems), and thus optimal rearing programs should be designed considering long-term consequences on milk yield.