As researchers search for new ways to support dairy cows through the transition period, the immune system may serve as a key to unlock important answers.
It has been well documented that cows experiencing ill health in the days and weeks immediately after calving usually fall behind their healthy herd mates in milk production and fertility. And one early postpartum health event often is linked to a cascade of others in the fresh-cow disease complex.
By monitoring inflammation levels of postpartum cows, we can gauge which animals are fighting disease challenges. During infections, such as mastitis or metritis, immune cells in the body recognize invading pathogens and become activated. Inflammation is one component of this immune response.
Inflammation plays an important role in promoting labor, expulsion of the placenta and uterine involution. Local inflammation accompanied by increased blood flow also can help cows resolve infections.
But longer-lasting, systemic inflammation is of greater concern for transition cows. Indicators of systemic inflammatory responses include increased body temperature, increased heart rate and decreased feed intake.
Research has shown that cows with the highest degree of inflammation produced less milk than those with the lowest level of inflammation throughout the first month of lactation. The difference was 20% on day 28 of lactation. Other findings suggest that stronger inflammatory responses during the first week of lactation are associated with decreased whole-lactation milk yield.
Several methods of preventatively treating postpartum inflammation have been explored by researchers in recent years. Administering non-steroidal anti-inflammatory drugs (NSAIDs) in the early postpartum period is the approach most widely studied, with varying results. Some research has shown an advantage in milk yield from postpartum NSAID treatment, while other studies showed no significant impact on milk yield.
In experimentally induced postpartum mastitis, NSAID therapy proved to have little impact on inflammation but did reduce somatic cell count and culling for mastitis. Another study showed NSAID therapy helped maintain ruminal contractions during induced mastitis, even though it did little to reduce inflammation. This support of rumen function could help prevent subsequent occurrence of displaced abomasum.
So far, studies that attempted to reduce postpartum inflammation as a strategy to reduce reproductive tract infections and support fertility have shown little promise in improving reproductive outcomes.
Unfortunately, health and productivity responses to anti-inflammatory treatment have been inconsistent, despite fairly consistent evidence that cows with heightened inflammation during the immediate days after calving produce less milk and suffer from more disease.
Ongoing research hopefully will bring additional clarity about the benefits and potential risks of several postpartum anti-inflammatory strategies. Scientists are exploring possible treatments to manage negative physiological and economic impacts of extreme inflammatory responses.