Dairy cattle are susceptible to increased incidence and severity of disease during the periparturient period.

A major contributing factor to increased health disorders is thought to be alterations in the immune system, Lorraine Sordillo, immunology specialist at Michigan State University, told audience members at the California Animal Nutrition Conference in May.

Uncontrolled inflammation is a major contributing factor to several disorders, such as mastitis, during the periparturient period. Dairy cows undergo several physiological changes during the onset of lactation that can impact the magnitude and duration of mammary gland inflammatory responses.

Oxidative stress, for example, occurs when there is an imbalance between the production of oxygen radicals during times of high metabolic demand and the reduced capabilities of the host's antioxidant defense. The progressive development of oxidative stress in transition dairy cattle is thought to be a significant underlying factor leading to dysfunctional inflammatory responses in both blood and mammary tissue compartments. Dairy cows undergo several other metabolic adaptations during the onset of lactation, which, together with oxidative stress, can further impact the magnitude and duration of inflammation. Specifically, the dramatic increase in energy requirements needed for the onset of lactation in transition cows is often accompanied by a decrease in voluntary dry matter intake that causes a negative energy balance (NEB). Energy requirements that cannot be met by the diet must then rely on tissue energy reserves. Therefore, NEB during the transition period causes mobilization of fat from tissue stores and the release of nonesterified fatty acids (NEFA) into the blood stream. The ways in which altered lipid metabolism, increased NEFA concentrations and oxidative stress can interact to initiate and promote uncontrolled inflammatory responses in transition cows are discussed in the paper that Sordillo presented at the California Animal Nutrition Conference.

Understanding more about the underlying cause of periparturient health disorders may facilitate the design of nutritional regimes that will meet the energy requirements of cows during early lactation and reduce the susceptibility to disease as a function of compromised inflammatory responses.