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COUNTRY LIFE IN BC • NOVEMBER 2016
Serotonin deflects milk fever in dairy cows But Holsteins respond differently than Jerseys
The chemical serotonin has been shown in a research study to increase calcium levels in the blood of Holstein
Research MARGARET EVANS
cows and the milk of Jersey cows right after birth at a time when, for many cows, calcium levels drop.
A research team led by assistant professor Laura Hernandez in the Department of Dairy Science, University of Wisconsin-Madison, studied the potential for serotonin to increase the calcium levels in both the milk and the blood of dairy cows. They 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
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were Holstein. Calcium levels in both the milk and circulating blood were measured throughout the experiment.
Dairy products such as milk, cheese and yogurt are the primary source of calcium for humans and the demand for
calcium-rich milk is high. But it takes a toll on dairy cows and some five to 10% of the North American dairy cow population suffer from hypocalcaemia (also known as milk fever), one of the most highly recognized diseases in dairy cattle among farmers. Calcium is essential for bone, tissue, smooth muscle and muscle strength and nerve function. However, the lowest concentration of blood calcium usually happens from 12 to 24 hours before calving, then returns to normal in a healthy cow within two to three days after calving. Hypocalcaemia is a major health issue in dairy cows. It is associated with
immunological and digestive problems, decreased pregnancy rates and longer intervals between pregnancies. In its clinical form, it can manifest as muscle tremors, cold ears/nose, and the cow often going down due to
insufficient calcium for muscle contraction. These all pose a
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Researchers aren’t sure why Jersey and Holstein cows react differently to serotonin but it is inspiring new research that could help dairy farmers improve herd health. (File photo)
problem for dairy farmers whose profitability depends upon regular pregnancies and a high yield of calcium-rich milk.
“All mammals get some form of hypocalcemia naturally at parturition to allow for mobilization of calcium from bone tissue to help with milk synthesis,” says Hernandez. “The diet of an animal (or human for that matter) is incapable of supporting both the mother’s physiology along with the synthesis of milk. Calcium can only be mobilized from bone
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concentrations fall below the normal systemic physiological concentration for an animal. That being said, dairy animals (and some litter-bearing species, like dogs) are more prone to hypocalcaemia because of the amount of milk they are producing. Dairy cows take a day or two after parturition to stimulate their natural bone resorption mechanism so they can struggle at birth with maintaining their own circulating calcium concentrations.”
Prevention
While there has been research into the treatment of hypocalcaemia, not much 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 knowledge, Hernandez and her team investigated the potential for serotonin to increase calcium levels in both the milk and blood of dairy cows.
“Our research has shown so far that serotonin stimulates production of the parathyroid hormone-related protein by the mammary gland,” she said. “This hormone is naturally produced by the mammary gland during lactation in order to activate the mechanisms necessary to stimulate bone resorption and therefore calcium liberation into the circulation.”
While serotonin improved the overall calcium levels in both the Holstein and Jersey cows, it happened in different
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. The serotonin treatment had no effect on milk yield, feed intake or on levels of hormones required for lactation.
“Most of our research has focused on the Holstein dairy cow on a large scale,” she said. “We do know that Jersey cows have higher milk calcium concentrations, as well as total fat and protein, than a Holstein. We are unsure why the two breeds respond in different ways but as dairy scientists, we do need to do more research on Jersey cows on the whole because it appears that their physiology is different than that of a Holstein.”
The team is currently working on numerous experiments to better understand the specific mechanisms that underlie serotonin’s actions during lactation and how it varies between the two breeds. The hope is that a procedure using serotonin can be developed as a preventative measure against
hypocalcaemia which would allow dairy farmers to maintain their cows’ health and milk production, as well as business profitability. The results of the study were published in the Journal of Endocrinology.
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