Milk production per cow is increasing. The period of peak milk production is in early lactation (within 30 to 60 d after calving) when the cow’s uterus is recovering and the cow is returning to estrous cyclicity. The competing processes of milk production, uterine involution, and the restoration of ovarian activity can be at odds, particularly if the unique metabolic processes that typify early lactation become imbalanced and the cow experiences negative energy balance and(or) metabolic disease during early lactation. A potential end result is that the cow does not become pregnant during the breeding period. Understanding the mechanisms that link the first 60 days of lactation with the subsequent reproductive success or failure is an important area of research for the dairy industry. The paper focused on glucose because of its dual purpose as a major component of cow’s milk and also a molecule that coordinates metabolic mechanisms that could possibly impinge upon postpartum uterine health and the subsequent establishment of pregnancy. There is ample evidence that hormones that support lactation can also act on the uterus and ovary to affect their function prior to and during the breeding period. In addition to the hormonal environment, the metabolic environment created by lactation that includes low blood glucose and elevated fatty acids and elevated ketones impinge upon the ovary as well as the immune system that plays a critical role in restoring uterine health in the postpartum cow. The specific mechanism through which the metabolic environment of early lactation deposits a lasting imprint on uterine and ovarian function is less clear. Also less clear are the mechanisms that link lactation to pregnancy loss in the lactating cow.
Autore: Dr. Matt Lucy, Professor of Animal Science, University of Missouri Animal Science Center
