Heat stress: A cool cow is more productive.

March 12, 2022

Heat stress: A cool cow is more productive.

One thing is sure, healthy cows are good for your bottom line. One of the most significant threats to your cows’ well-being is heat stress which can impact their milk production and yours. In this article we’ll look at the effects of heat stress, along with a management plan so that you and your cows stay productive.

Just Because You’re Comfortable Doesn’t Mean Your Cows Are.

Cows produce a lot of heat and they can handle the cold quite well. What’s less well known is they can overheat in temperatures that might seem comfortable for you and your staff. Here’s how the numbers break down: a temperature of 25°C with a humidity of 60% is considered a mild stress. A temperature of 30°C with a humidity of 80% puts your cows in danger of severe overheating.

As a farmer you’ve got a lot invested in your heard and it might be surprising just how significantly heat stress can affect the entire production cycle. Heat stress is not a one-off problem. Once a cow is affected their whole system is knocked out of kilter. They’re less able to feed and ruminate. Kidneys and lungs decrease in efficiency, affecting pH and sodium levels in the blood stream. The ovaries are disturbed reducing reproductive abilities and resulting in higher calf mortality rates. Even the hooves suffer because your cows are standing for longer periods of time to cool off which can lead to problems such as lameness . The result is reduced quality and quantity of milk production along with physical discomfort for your animals and psychological stress.

To fully understand the trauma of heat stress, think of it as if your heard has gone into collective hyperthermia. Your cows, now aware they are in distress, start conserving energy, slowing their whole system down until the next birthing cycle.

Obviously heat stress can quickly become a nightmare situation, one you’d like to avoid. So how do you know if your cows are suffering?

1. Your Cows Know What’s Going On.

The first thing to do is take a good look at your herd. Have there been any changes in behaviour? Are they breathing more heavily? Drinking more water? Is their excess saliva in their mouth? Signs such as cattle laying down repeatedly then getting up to walk around could also indicate they’re uncomfortable and trying to reduce their discomfort.

Your animals will also avoid certain areas of the barn, bunch together under one fan. Basically, once your cattle start overheating they’ll be looking for ways to find fresh air and cool down.

2. How Hot. How Damp.

The next thing to verify are your temperature and humidity levels, otherwise known as the temperature and humidity index or TH1. Thankfully, today you can avoid complicated charts and calculations by managing the TH1 easily with your smartphone. Free apps have been developed for both Android and iOS that can help breeders monitor the THI in their stalls.

3. How’s the Housing?

You’ll need to evaluate your barn. Are there obstacles preventing fresh air reaching your cows? The robotic milker and the milking box, the watering station, even other cows in free stalls are just a few examples of how fresh air might be blocked. To check for dead spots, once again look to your herd to see if they’re avoiding certain areas.

You’ll also have to consider your present ventilation system in your barn.

If you’re relying on natural ventilation, the challenge is that hot weather doesn’t necessarily coincide with windy conditions. Likewise, chimneys on their own have limits because the temperature difference between indoors and out is insignificant. The drawbacks of this system include:
• wall openings that don’t extend to ground level
• lack of complementary mechanical ventilation
• insufficient number or improper placement of fans

If you’ve got a cross-ventilation system in place, there are other difficulties:
• air flows above cow level and along the ceiling before being exhausted through the fans
• air flows down the alleys and walkways instead of over and around the cows

Heat Stress Management: Water and Air to the Rescue.

Let’s break down why sprinklers combined with fans are considered one of the most recommended cooling systems to keep your cows comfortable.

Wind forced over the cows, or convective cooling, can alleviate heat stress, but there can be a problem. Once heat stress is reached, convective cooling may not be enough and evaporative cooling should then be added.

Evaporative cooling is divided into two sub sections, indirect or direct.

Indirect evaporative cooling uses fogs or misters to lower the air temperature, which is then circulated around the cows. Indirect evaporative cooling is an effective method, but high humidity could hinder evaporation.

Direct evaporative cooling uses sprinklers to wet the cow’s skin and then uses fans running continuously to evaporate the water off the skin.

Put this together and depending on your situation, fans with sprinklers or misters is the best way to beat heat stress.

Consider the Climate is Changing and So Are the Cows.

In the past, farmers had to worry about extreme heat for a few days during the hotter months. With global warming, temperatures once considered tropical are no longer atypical in the United States, Canada and Europe. The result – the number of days when the TH1 passes the comfort zone is steadily increasing.

Not only is our climate changing, so are our cows. Dr. Pete Hansen, professor of animal science at the University of Florida, confirms that heat stress is a major problem for dairy cows impacting milk production and fertility. However, he goes on to add, “As we continue to improve milk yield per cow genetically, nutritionally or through other management strategies, we’re also making cows that are more susceptible to heat stress. The cow of tomorrow will be more sensitive to heat stress than the cow of today. ”

Hansen makes a parallel between the modern dairy cow and a furnace. “Just like a furnace, she takes fuel sources (feed) and burns that fuel to produce heat,” he explained. “If cows produce more milk, they need to burn more fuel and more energy to power the synthesis of milk, and as a result, the heat production of the cow increases.”

The Best Plan: Prevention is Worth a Pound of Cure.

The best way to manage heat stress is to act before your cows are suffering and to protect them from the impact of overheating. Consider your water supply, feed management and housing, but most importantly your fresh air supply. Check your air circulation capacity and increase the rate when necessary with mechanical ventilation.

Heat stress can be prevented, just don’t wait until the cows are suffering to turn on the fans.