Happier cows may give more calcium-rich milk, according to a new study which could lead to a better understanding of how to improve the health of dairy animals, and keep the milk flowing.
Daily infusions with a chemical commonly associated with feelings of happiness were shown to increase calcium levels in the blood of Holstein cows and the milk of Jersey cows that had just given birth.
Demand is high for milk rich in calcium: there is more calcium in the human body than any other mineral, and dairy products such as milk, cheese and yoghurt are primary sources of calcium.
Hypocalcaemia is considered a major health event in the life of a cow. The risk of this disease is particularly high immediately before and after cows give birth.
It is associated with immunological and digestive problems, decreased pregnancy rates and longer intervals between pregnancies.
These all pose a problem for dairy farmers, whose profitability depends upon regular pregnancies and a high-yield of calcium-rich milk.
Whilst there has been research into the treatment of hypocalcaemia, little research has focused on prevention.
In rodents it has been shown that serotonin (a naturally-occurring chemical commonly associated with feelings of happiness) plays a role in maintaining calcium levels.
Based on this, a team from the University of Wisconsin-Madison, led by Laura Hernandez, studied the potential for serotonin to increase calcium levels in both the milk and blood of dairy cows.
The team 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 (compared to controls).
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 Hernandez.
“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,” she said.
The study was published in the Journal of Endocrinology.
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