Metabolic programming in dairy cattle

Abstract

In humans, there is increasing evidence that metabolic diseases occurring in later life arise in utero as a result of programming of key endocrine systems during suboptimal intrauterine conditions, which are often associated with fetal growth retardation. The process by which insults during early life lead to permanent changes in tissue structure and function and finally to low birth weight (BW), is known as intrauterine or developmental programming. Because fetal growth depends primarily on the supply of nutrients and oxygen, intrauterine programming of adult phenotype has been attributed most commonly to poor nutrition in utero. Also other factors like environmental temperature, oxygen availability and even overnutrition have been shown to have a significant impact on intrauterine growth and development. Since the placenta is the main organ for communication between mother and fetus, it is clear that placental insufficiency invariably affects embryonic development and health in later life. In order to optimize income over costs, dairy farmers inseminate their nulliparous heifers at adolescent age (14 -15 months), and subsequently strive for calving intervals not longer than 380 days. The latter implies that heifers are still growing and multiparous animals are still yielding large quantities of milk while being pregnant. Dairy cows heavily selected for high milk yield, have specific endocrinological characteristics like low peripheral insulin levels and low peripheral insulin sensitivity, both contributing to safeguard glucose for milk production. Backside of this strongly advanced selection for yield, is the high incidence of a wide range of metabolic diseases that furthermore negatively influence both production and fertility of the cows. Besides, modern dairy cattle are ill-famed for their very short life expectancy. Although dairy cows are well fed during gestation to sustain their high yields, they partition lots of nutrients to the udder despite being pregnant. These nutrients are hence withdrawn from both placental and fetal development. Evidence from epidemiological studies is now available demonstrating that milk yield during gestation and environmental factors such as season of pregnancy and parturition influence both the size as well as the intermediary metabolism of the neonatal calf. The latter suggests that further optimization in terms of production, reproduction, general health and longevity in the dairy sector might be feasible by taking into account environmental factors occurring during pregnancy. [...]