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Story written by: Christie Delfanian

Rosemary and dairy cows could be a winning combination.

A natural antioxidant, anti-inflammatory compound found in rosemary plants can improve milk production and possibly help dairy cows weather the stressful post-calving period, according to a small Department of Dairy and Food Science pilot study led by graduate student Tainara Michelotti.

“The transition time involves drastic changes in metabolism and physiology as the animal goes from being pregnant to full-on lactation,” said assistant professor Johan Osorio, who oversaw the study. Within the first week after giving birth, cows can produce anywhere from six to 10 gallons of milk per day. “That’s a lot for the body.”

An estimated 75% of the health issues in adult cows occur within the first month after calving, according to an article in the Journal of Dairy Science. The productive life of a dairy cow is, on average, three to four years, so minimizing problems during the transition period can help improve longevity—and the producer’s bottom line.

Carnosic acid, which is relatively abundant in rosemary leaves, has shown high antioxidant activity in human and mouse studies. However, this is the first time the compound has been tested in dairy cows.

Initial study results were published in a special edition on Gestational and Lactational Redox Signaling and Oxidative Stress in Dairy Cows.

The study was supported by U.S. Department of Agriculture Hatch funding through the South Dakota Agricultural Experiment Station. In addition, Osorio and Michelotti received a $5,000 ������Ƶ Research, Scholarship and Creative Activity (RSCA) Challenge Fund grant for the research. The RSCA funding gave Michelotti, who received her master’s degree in December, the unique experience of getting and administering a grant.

Promising initial results

Cows that received a daily IV infusion of carnosic acid for three days after calving produced around 9.9 pounds more milk per day—a gallon of milk is 8.6 pounds. That milk also had a higher protein yield than the milk from the control group.

When cows are going through this transition, they typically do not eat enough to get the nutrients needed to keep up with milk production. Therefore, to sustain this output, the body pulls out energy from fat reserves through a process known as lipid mobilization and puts them into the mammary glands to produce milk.

That comes at a cost to the animal. Osorio compared the lipid mobilization that occurs when cows metabolize stored fat to what happens to people who are diabetic when their bodies cannot produce enough insulin. The buildup of excessive fat in blood and in the liver can lead to a condition called ketosis.

However, analysis of blood samples suggests the cows that received carnosic acid were able to cope with increased milk production without increased liver damage and risk of health disorders, such as ketosis. The pilot study results “demonstrate that carnosic acid promotes positive responses on inflammation and oxidative stress biomarkers.”

Further analysis needed

The liver plays a key role in energy metabolism for postpartum cows. “When cows have a bad transition, it usually comes down to the liver,” Osorio said. Consequently, follow-up work is being done to study how liver cells respond to carnosic acid.

“We are growing liver cells, incubating them with the rosemary extract and then challenging them with an oxidative agent,” he explained. Oxidative stress is one of the challenges in transition cows.

The follow-up data and the pilot study results will be used to apply for USDA funding for a larger study to confirm the initial findings. Both the dosage and the timing of the carnosic acid infusions may also be variables to examine in future studies.

Integrating rosemary leaves or powders into animal feed may be possible. However, Osorio said, “We must determine the half-life of the actual compound in the rosemary plant and how long it will last in the cow to help determine how much the animal must consume.”

Another research group integrated 10% to 20% rosemary plants into the diets of dairy goats and found carnosic acid in the milk and the blood of their offspring. That suggests what is good for the cow might also be good for the calf and for human consumption.