While you’re sleeping in the early morning hours, dairy producers are already out on their farms. It’s hard work; stalls must be cleaned and supplies must be restocked. Cows must be fed and milked. Sick cows must be treated and monitored.
One of the groups of cows at highest risk of illness is newborn calves; most of those deaths occur during the first 60 days of life. In the United States, the average national mortality rate for calves fluctuates between 6 and 10 percent, and 80 percent of those deaths are due to infectious diseases.
Vaccination sounds like the obvious solution, but calves’ immune systems aren’t developed enough for vaccines to be fully effective. By the time their immune systems would be responsive, the calves may already be infected with a disease. This leads to the use of antimicrobials.
Treating neonatal diseases is one of the main reasons antimicrobials are used on farms; but ultimately, this practice may damage the calves, dairy consumers, and the environment. Dairy producers also take a hit; approximately 20 percent of total dairy production cost goes toward rearing costs, which involves replacing production cows.
"The use of antimicrobials is needed to treat animals, and their use should be encouraged on animal welfare grounds when the calves are clinically sick," says Dr. Ángel Abuelo, assistant professor in Cattle Health and Wellbeing. "However, the usage of antimicrobials leads to the generation of antimicrobial-resistant bacteria in both commensal and pathogenic bacteria."
Abuelo is working to solve this problem. In his new research group at the MSU College of Veterinary Medicine, he is working with Dr. Lorraine Sordillo, the College’s Meadow Brook Chair in Farm Animal Health and Wellbeing, to ramp up the calves’ immune systems so earlier vaccinations might be effective.
“If we decrease the number of female calves who die each year from diseases, then the farmer can raise more heifers and increase their profitability,” says Abuelo. “If we can increase the prevention of infectious diseases in calves, there also will be an associated decrease in antimicrobial use on farms. Increasing disease resistance by increasing immunity reduces the use of antimicrobials for both prophylaxis and therapeutic purposes and, therefore, the likelihood of antimicrobial resistance will decrease."
In an effort to do this, Abuelo is looking at the impact of oxidative stress on vaccine responsiveness in neonatal dairy calves. Oxidative stress occurs in a body when there are too many free radicals in comparison to antioxidants. When this happens, important immune cells called lymphocytes become oxidized; just like rust on a car or fruit that starts to go brown, the lymphocytes’ functionality starts to decrease. Without enough antioxidants, oxidative stress continues to damage lymphocytes and lower the body’s immune response, making it susceptible to infectious diseases.
“It’s a balance,” says Abuelo. “Some free radicals are good; they’re generated as a byproduct of metabolism, to kill some specific bacteria and other key physiological processes. But too much means too many free radicals that inhibit the body’s ability to kill bad bacteria.”
The calves dying from infectious disease first experience oxidative stress. Abuelo’s laboratory is focusing on using antioxidants to control oxidative stress, which may help their immune systems be more responsive to vaccines. To do this, Abuelo is isolating lymphocytes from neonatal calf blood to study which immune functions become altered under oxidative stress. He wants to find out if it’s possible to restore those functions using micronutrients in the form of antioxidants.
“Success in this study could lead to new management practices that use feed to deliver these micronutrients to the calves,” says Abuelo.
The theory is promising. This year, Abuelo’s research proposal was awarded $500,000 by the United States Department of Agriculture, the National Institute of Food and Agriculture, and the Agriculture and Food Research Initiative.
“This research could help dairy producers to produce replacement cows at a lower cost, improve the health of those animals, decrease the number of sick cows, and reduce the use of antimicrobials,” says Abuelo. “It would be a win for everyone.”