Daily infusions with serotonin, a naturally-occurring chemical associated with feelings of happiness, were shown to increase calcium levels in both the blood and milk of dairy cows. The results could lead to a better understanding of how to improve the health of milk-producing cows.

About 5-10% of the North American dairy cow population suffers from hypocalcaemia – in which calcium levels are low. The risk of this disease is particularly high immediately before and after cows give birth.

Whilst there has been research into the treatment of hypocalcaemia, little research has focused on prevention.

In rodents it has been shown that serotonin plays a role in maintaining calcium levels.

Based on this, a team of scientists at the University of Wisconsin-Madison investigated the potential for serotonin to increase calcium levels in both the milk and blood of dairy cows.

The researchers 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 Holstein – two of the most common breeds.

Calcium levels in both the milk and circulating blood were measured throughout the experiment.

Whilst serotonin improved the overall calcium status in both breeds, this was brought about in opposite ways.

Treated Holstein cows had higher levels of calcium in their blood, but lower calcium in their milk.

The reverse was true in treated Jersey cows and the higher milk calcium levels were particularly obvious in Jerseys at day 30 of lactation – suggesting a role for serotonin in maintaining levels throughout lactation.

“By studying two breeds we were able to see that regulation of calcium levels is different between the two,” said lead author Dr. Laura Hernandez, from the Department of Dairy Science at the University of Wisconsin-Madison.

“Serotonin raised blood calcium in the Holsteins, and milk calcium in the Jerseys. We should also note that serotonin treatment had no effect on milk yield, feed intake or on levels of hormones required for lactation.”

The findings were published in the July 1 issue of the Journal of Endocrinology.

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Samantha R. Weaver et al. 2016. Elevation of circulating serotonin improves calcium dynamics in the peripartum dairy cow. J. Endocrinol. 230: 105-123; doi: 10.1530/joe-16-0038