Warm temperatures not only make cows sweat, they also cause intestinal problems in cattle: a mechanism for cooling the digestive tract makes the intestinal wall permeable to bacteria when it is hot. This can promote inflammation and costs the animals energy. In view of the increasingly frequent heat waves caused by climate change, scientists are therefore looking for ways to bring relief to dairy cows in particular.
Not only people suffer from extreme temperatures in summer, but cows also have to struggle with the heat. The increasing occurrence of heat waves and other extreme weather events poses health and economic challenges for farmers and their animals. Dairy cows are particularly sensitive to heat: they show the first signs of heat stress from an outside temperature of 15 degrees Celsius and a humidity of 70 percent. They lie less, eat less, breathe faster and have an increased heart rate. If the ambient temperature rises even further, the body temperature increases and the cows start panting. As a result, they lose large amounts of fluid and minerals and produce less milk.
Heat makes cow intestines more permeable
But the heat also has other effects: In order to dissipate the heat from the body surface, the blood flow in the intestines of dairy cows is reduced. As a result, your intestinal wall becomes more permeable, which in turn can lead to inflammatory reactions in the intestine and the adjacent lymph nodes. Because the protective barrier of the intestines, which has become permeable due to heat, now clears the way for bacteria and other pathogens, which can penetrate more and possibly deeper into the layers of the intestine. This clinical picture also occurs in people suffering from celiac disease or Crohn's disease, but heat is not the trigger here.
This so-called "leaky gut" syndrome can not only cause inflammation, it also costs the dairy cows more energy because the immune system now has to work much harder to fight the effects. But what exactly happens with the heat-related syndrome and how the immune system and energy balance of the cows react to it has not yet been sufficiently researched. A team led by Franziska Koch from the Research Institute for Livestock Biology in Dummerstorf is therefore investigating the effects of the "leaky gut" syndrome in more detail in order to develop new solutions for the feeding and husbandry conditions of dairy cows during heat waves. These should primarily serve the health and well-being of the cows, but also counteract the economic losses caused by the lower milk yield.
What is happening in the cow?
For their project, the researchers kept dairy cows at different ambient temperatures. The control group was exposed to an ambient temperature of 15 degrees, while another group of dairy cows was housed in a climate room with temperatures of 28 degrees. "The first results have produced amazing things," reports Koch. "It could be shown that heat-stressed animals do not use fat reserves to compensate for the lack of energy. Instead, under heat stress, cows break down their own proteins to generate energy. This ensures that less heat is generated when nutrients are broken down and the cow does not get any warmer,” reports Koch.
The dairy cows have therefore found an alternative way to generate energy that does not make the heat situation even worse. However, this does not solve the problem of increased inflammation caused by heat stress. An additional examination with thermal cameras revealed, among other things, that the udder is the hottest part of the dairy cow's body. There, the risk of mastitis increases when ambient temperatures are high.
remedy sought
As dairy cows will increasingly face summer heat stress as climate change progresses, the research team believes it is of the utmost importance to develop measures that make it easier for cows to cope with the heat. "It is important to understand the basic mechanisms of heat stress in order to develop practical solutions for livestock farming," emphasizes Koch. "Cooling down with the scarce resource of water is not always a sensible alternative, while the installation of fans in the stables would be a sensible investment, but it would involve high energy and investment costs". With the conclusion of the research project "LeakyCow" in the coming year, the first concrete proposals for improved heat stress management for dairy cows will be presented.
Source: Research Institute for Livestock Biology (FBN)