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Some cows make more nutritious milk when happy (2016-08-11)


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 birth.

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.

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 problem for dairy farmers, whose profitability depends upon regular pregnancies and a high-yield of calcium-rich milk.

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 cows.

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.

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.

"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 postinfusion.
Blood and urine were collected daily before the infusion period, for 14 days postpartum and on day 30 postpartum.
Milk was collected daily during the postpartum period.
Feed intake and milk yield were unaffected by 5-HTP infusion postpartum.
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 treatment.

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.

See also
Study finds clear differences between organic and non-organic products

For more information
Journal of Endocrinology
Elevation of circulating serotonin improves calcium dynamics in the peripartum dairy cow
published 1 July 2016.