Heat Stress Mitigation Is a Worthwhile Investment
Published on Fri, 06/04/2021 - 10:39am
Heat Stress Mitigation Is a Worthwhile Investment.
By Jaclyn Krymowski.
Excessive heat to dairy cattle is more than just a bit of seasonal discomfort. When they’ve reached the point of heat stress – which can happen around 75°F for most cows – they become less productive, less efficient and significantly less comfortable.
This condition is essentially the inability of a body to get rid of excess heat. As a result, the core temperature rises, forcing both the heart rate and number of breaths per minute to increase.
Different environmental and animal conditions will have varying effects on just how severe the consequences of heat stress will be in each case. But even when relatively minor, dairy animals will begin to drop off in their milk production and feed intake. In extreme situations, heat stress can be lethal especially for weak and vulnerable animals.
According to a 2019 study done by the Department of Agriculture’s Agricultural Research Service, heat stress is responsible for a loss of $897 to $1,500 million in revenue loss each year for the U.S. dairy industry.
Putting numbers to this economic stake illustrates how designing facilities with heat in mind isn’t just part of good animal husbandry practices – it’s a lifelong investment.
Quantifying the impact
Part of avoiding heat stress is first understanding a cow’s biological system. The primary way cattle dissipate heat is through convection by means of sweating. Cows do not sweat nearly as much as people or their equine counterparts. This makes them much more susceptible to becoming heat stressed and resorting to other dissipation measures such as panting.
It is usually when temperatures are in the mid-70°Fs when cattle start becoming truly heat stressed, but the humidity index can greatly increase susceptibility even at lower temperatures. A humid environment makes it much more difficult for body heat to naturally dissipate despite sweating and panting. In the industry, temperature-humidity index (THI) is a formula used to quantify heat stress in its relation to the environmental conditions, according to a 2020 review from China.
Once THI has reached a certain point, the symptoms become evident with panting, increased body temperature, a drop in milk production, a change in milk components and decreased ruminations. Research has also found that an increase in body temperature can reduce fertility rates and the likelihood of a cow settling after A.I. service. Likewise, donor cows are less likely to maintain an embryo when they have an irregular body temperature.
As cattle become uncomfortable, they are more likely to spend less time moving – even when they come into heat. This can make estrous detection difficult during the summer months, even with activity monitoring.
This cascade of events, ultimately, begins one the cellular level as individual cells are unable to remove the excess heat to function efficiently.
One 2010 study in the Journal of Dairy Science found that insulin, which enhances glucose utilization, may be a crucial part of the body’s heat stress response. Several other studies have also supported the idea that adequate nutrition is essential to equip the cow’s metabolism to better regulate heat.
However, all the nutrition in the world will not entirely prevent overheating in a given environment – it will just help the cow’s body better respond to it. This is why things like shade, adequate fresh water and misters are essential.
Steps to mitigate heat
There have been extensive studies done on the best ways to cool cows in a variety of climates. Many of these are relatively simple fixes, but they may require an active investment or adjustment of facilities.
One of the best ways to help cows stay cool is the simplest – shade. One Florida study found cows with access to shade had six to 10% more milk yield, plus lower body temperatures, compared to those who did not.
Likewise, when coupled with heat abatement techniques such as natural ventilation, fans and sprinklers, shade can become even more effective.
In pastoral situations, it is preferable to have accessible shade, but outdoor sprinkler set ups have also been made to work quite well.
Keep in mind that when shade or sprinklers are offered, cows may be inclined to crowd together, which will reduce the effectiveness of cooling. Try to provide enough shade and/or misters for animals to be spaced out.
To handle the metabolism side of heat stress issue, additives can enhance the way glucose is utilized. This can help keep dry matter intake up and help cows be able to dissipate heat. However the effectiveness of these different products can vary, so research and consultation should be done be done before making a decision.