Happy cows produce more calcium. So says a study published recently in the Journal of Endocrinology by researchers at the University of Wisconsin.

People who consume a standard American diet rely on dairy products such as milk, cheese and yogurt as a primary calcium source. However, estimates are that 5 to 10 percent of dairy cows in the United States have hypocalcemia (hi-po-cal-SEE-me-a), or low levels of calcium in the blood. The cows are most at risk for low calcium immediately after giving birth

The Wisconsin research team found that giving certain breeds of cows daily doses of a chemical that boosted serotonin production also increased calcium levels in the animals. Serotonin is a chemical the body produces that, among other things, is generally linked to increased feelings of happiness and well-being.

The study involved dairy cows from the two most common breeds. Half were Holstein cows, while the other half were Jerseys. For seven days — at two-, four- and eight-hour intervals — the researchers continually measured calcium levels in the cows’ milk and blood after boosting serotonin levels. In the Holsteins, the serotonin boost directly increased calcium levels in the blood. The Jersey cows also showed increased calcium in their milk.

The researchers noted that calcium deficiency is linked to problems with a cow’s immune and digestive system, as well as lower pregnancy rates and longer intervals between pregnancies.

They hope their findings can help dairy farmers run more profitable businesses — and ensure that cows remain happy and healthy, and produce calcium-rich milk.