US scientists have found some cows given daily infusions of serotonin produced milk that contained more calcium.

Dairy cows given daily doses of the "feel good" drug serotonin produced milk higher in calcium, say US scientists.

Calcium is a key nutritional component of milk, but many dairy cows suffer from a condition known as hypocalcaemia, a metabolic disorder that affects dairy cows during the transition from pregnancy to lactation.

Researchers from University of Wisconsin Madison infused a chemical that converts to serotonin into 24 dairy cows in the run up to giving birth.

Half the cows were Jersey and half were Friesians, two of the most common breeds in Australia.

In the Jersey cows it led to higher milk calcium levels.

It only increased calcium in the blood of the Friesians but not in their milk.

According to the study, published in the Journal of Endocrinology, hypocalcaemia is considered a major health event in the life of a cow.

It is associated with immunological and digestive problems, decreased pregnancy rates and longer intervals between pregnancies.

These all pose a problems for dairy farmers whose profitability depends on regular pregnancies and a high demand for calcium-rich milk.

Among the many benefits of a diet high in calcium is good bone health to prevent osteoporosis.

The next step for the researchers is to investigate how serotonin regulates calcium levels across different breeds.

Serotonin is a chemical messenger that's believed to act as a mood stabiliser. It can also affect the functioning of our cardiovascular system, muscles, and various elements in the endocrine system.

Previous research has found evidence that serotonin may play a role in regulating milk production in the breast.

"We would also like to work on the possibility of using serotonin as a preventative measure for hypocalcaemia in dairy cows," said lead author Laura Hernandez.

"That would allow dairy farmers to maintain the profitability of their businesses, whilst making sure their cows stay healthy and produce nutritious milk, " she said.