Hypocalcemia is a metabolic disorder that affects
dairy cows during the transition from pregnancy to
lactation. 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
Demand is high for milk
rich in calcium: there is more calcium in the human
body than any other mineral, and in the West dairy
products such as milk, cheese and yoghurt are
primary sources of calcium. But this demand can take
its toll on milk-producing cows: roughly 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.
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 problem for dairy farmers, whose profitability
depends upon regular pregnancies and a high-yield of
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 Dr Laura Hernandez,
investigated the potential for serotonin to increase
calcium levels in both the milk and blood of dairy
The team infused daily
for approximately 7 days prepartum with either
saline or 1.0mg/kg bodyweight of the immediate
precursor to serotonin synthesis,
5hydroxy-l-tryptophan (5-HTP) 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.
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
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
"We should also note
that serotonin treatment had no effect on milk yield,
feed intake or on levels of hormones required for
lactation" says Laura Hernandez.
The next steps are to
investigate the molecular mechanism by which
serotonin regulates calcium levels, and how this
varies between breeds.
We would also like to
work on the possibility of using serotonin as a
preventative measure for hypocalcaemia in dairy cows,
continues 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.
On infusion days, blood
was collected before, after, and at 2, 4, and 8h
Blood and urine were collected daily before the
infusion period, for 14 days postpartum and on day
Milk was collected daily during the postpartum
Feed intake and milk yield were unaffected by 5-HTP
Cows infused with 5-HTP had elevated circulating
serotonin concentrations prepartum.
Infusion with 5-HTP induced a transient hypocalcemia
in Jersey cows prepartum, but not in any other
Holstein cows infused
with saline had the highest milk calcium on the day
of and day after parturition.
Postpartum, circulating total calcium tended to be
elevated, and urine deoxypyridinoline (DPD)
concentrations were elevated in Holstein cows
infused with 5-HTP.
Overall, Jerseys had
higher urine DPD concentrations postpartum when
compared with Holsteins.
Study finds clear differences between organic and
For more information
Journal of Endocrinology
Elevation of circulating serotonin improves calcium
dynamics in the peripartum dairy cow
published 1 July 2016.