Just like stress in humans, stress in cows isn’t like other diseases we treat. Instead of being diagnosed the cow is sick or the cow is not, stress is something that amasses as one stress piles on top of another.
It was a keynote topic at the recent Penn State Dairy Cattle Nutrition Workshop where multiple speakers highlighted the importance of understanding what stress is and how cows respond to it.
“What is stress? There’s a ton of different definitions,” introduced USDA Agricultural Research Service’s Jeff Carroll as he spoke of its effect on cattle. “The problem we have with trying to define stress is that it’s an engineering term that we are applying to the flight or fight response.”
Carroll went on, “Stress is a coordinated set of biological responses that has an effect on the homeostasis of animals.” This stress can be physical, social, nutritional, and/or psychological.
Stress responses and immune responses are closely tied. “When we initially activate the stress response, we are actually priming the immune system,” Carroll explained.
Acute or chronic?
While acute stress has been tied to beneficial immune function enhancement, more chronic stress represses the immune system. “Long-term stress, for example, food restriction or inclement weather, realigns immune systems and the situation enters immune suppression,” Carroll explained.
A number of things including age, breed, environment, gender, nutrition, personality, metabolic, maternal influence, and health all factor into the stress response. Additionally, it’s important to note that they all interact and overlap.
Huge nutritional impact
That stress response requires additional nutrients and energy especially. Carroll pointed out that this energy requirement often occurs at a time when cows are intaking less feed. “Cows have a 10 to 13 percent increase in metabolism for every 1°C increase in body temperature,” Carroll detailed that need. “We have to realize beyond the effects of glucocorticoids on tissues, we have to pay attention to the energy demands of animals during this time.”