Getting ahead of heat stress

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In the past four decades, we've seen a massive leap in milk production per cow. These are all thanks to nutrition, genetics, and even management innovations. But let's not kid ourselves; it's a double-edged sword.
Sure, we're seeing bumper milk yields, but we're also witnessing increased heat stress issues among lactating and close-up cows. This is especially true during the warmer months. It's like the more we step up the milk game, the more we're turning up the heat stress dial.

What is Heat Stress?

As cows digest their food and produce milk, they generate heat. Add the heat they absorb from the sun, and you have a heat production factory on four legs.
But what happens when this "four-legged factory" starts to overheat? That's when we encounter a phenomenon known as heat stress. It's a bit like when your laptop gets too hot after hours of use and starts to slow down. Like your laptop, cows have ways to stay cool. They can expel some heat through breathing, sweating, or relying on a cold wind.
However, when the heat they're producing and absorbing outpaces their ability to cool down, their body temperature rises.
Heat stress takes a toll on a cow's productivity. When the mercury rises, cows eat less dry matter. That means less fuel, causing a nosedive in milk production. But the ripple effects don't stop there. Heat stress also messes with the cows' reproductive cycles, leading to lower pregnancy rates and smaller calves.
And you know what's worse? Heat stress leads to elevated body temperatures, more time spent standing, extended periods between pregnancies, and, sadly, even higher mortality rates.
Because of this, wise dairy farmers don't let their cows suffer in the heat. They're proactive, implementing various strategies to help their cows keep cool when the weather heats up.

What is meant by Temperature-Humidity Index (THI)?

 Have you ever wondered how we measure the heat stress a cow experiences? This is done through the temperature-humidity index, or THI for short. It's like the heat index for humans, but for cows.
High-producing cows start to feel the heat when the THI hits 65. For every point above that, they lose about a pound of milk per day. And the losses mount up as the heat stress level and duration increase.
But don't worry; it's not all doom and gloom. Cows are resilient. Give them a few hours of respite from the heat each day, and they can bounce back from a few hours of heat stress. It's a reminder of the importance of smart farm management.
Heat stress in cows isn't just about the temperature-humidity index (THI). It's a complex puzzle with many pieces. And if you look at the standard methods farmers use to keep their cows cool, you'll get a glimpse of what those pieces are. Take shade, for instance is a strategic move to reduce the heat they soak up from the sun.
Then there are the mixing fans. They're not just for a cool breeze. They increase convection, helping the cows shed more body heat into the air.
And what about those sprinklers you see on dairy farms? When the water on the cows' skin evaporates, it takes some of the heat with it.
Even the misters have a role to play. They lower the air temperature around the cows.

Why high-producing cows are more at risk of heat stress

Let's talk about the top cows in the dairy industry: those with high production rates. They produce the most milk, but, as they say, with great productivity comes great heat generation. Because they eat more, high achievers also generate more heat. So much so that even in a well-ventilated barn, they can feel the heat at 65°F.
To put it in perspective, a cow producing 100 pounds of milk daily also produces over 1,500 watts of heat. Compared to a cow providing 1,200 watts of heat and 70 pounds of milk, it is a whopping 26 percent more energy.
That is why cows love shade. It's a survival strategy as much as just being about comfort. Even at temperatures below 65°F, those creatures can feel the pinch of heat stress. In fact, a cow soaking up the sun has to dispel a whopping 300 watts more than its counterpart chilling in the shade. That is why shade is essential for cows.

Increase cow comfort with proper ventilation

Aside from shade, there is another way to keep cows cool and comfy. Increasing air velocity is the key! When you amp up the air speed around our bovine friends, you help them shed that unwanted heat. Think of it as giving them their own personal wind tunnel experience. Cross-ventilation with baffles, tunnel ventilation, or high-speed mixing fans are some snazzy methods to do this. Consider this interesting fact: a cow producing 100 pounds of product every day would generally pant at 68 beats per minute (bpm). This holds true at an airspeed of just 3 mph and a THI (Temperature Humidity Index) of 75. In contrast, a 70-pound cow would breathe at 53 beats per minute.
Meanwhile, you can also use more fans. When you place the fans overhead, you can create a breeze reaching speeds of more than 10 mph. But positioning the fans is only one aspect of doing it correctly. These fans must be installed high and away from people, livestock, and other objects like machinery. You don't want any unexpected run-ins.
Lastly, here's a pro tip: direct those fans toward the cows. The sweet spot is the 20-degree angle.

Effective Water-Cooling Techniques for Cows

Cows benefit significantly from water cooling. In fact, sprinklers have a dual function: they wet the cow's skin, and the heat from the cow's body helps to evaporate the moisture. However, this process is energy-intensive, consuming approximately 1,040 BTUs per pound of water evaporated.
Misting systems operate on a similar principle. They cool the surroundings by turning water droplets into vapor, utilizing the ambient heat. While both sprinkling and misting contribute to an increase in relative humidity, a well-ventilated barn ensures that this rise doesn't reach uncomfortable levels.
It's important to note that these techniques perform better when the dew point is lower, and the weather is generally dryer. Giving the water enough time to evaporate while using sprinklers adequately is essential. Additionally, care should be taken to avoid over spraying, as this could result in unwanted dampness around the udder.

Why Cooling Is Important in Holding Areas

Holding areas in milking facilities require effective ventilation and cooling, particularly during the warmer seasons. This is primarily to prevent the onset of heat stress. The reason why cooling holding areas is important? Cows are confined in these spaces, even up to an hour. It's worth noting that cows will have lesser airflow and exposed surface area when holding areas are crowded.
Interestingly, even a tiny 20 percent reduction in this exposed area can have a big impact. For instance, a cow producing about 70 pounds per day, may see her breathing rate spike from a normal 53 to a concerning 85 breaths per minute. This accelerated rate clearly indicates that the cow is inching closer to moderate or even severe heat stress.

Assessing Heat Stress in Cows

When it comes to gauging heat stress in cows, two reliable indicators stand out: respiration rates and body temperature. These metrics offer insights into how efficiently cows balance their heat production and dispersion, especially during warm periods. It's essential to note that not all cows are the same; some will exhibit varied responses to heat.
To get a clear picture, you can record either the respiration rates or body temperatures at different intervals throughout the day. This method can help evaluate the effectiveness of your cooling strategies. It's also beneficial to keep tabs on daily milk production. Remember, though, that any decrease in milk production typically appears a few days after cows start to experience heat stress.

Ensuring Peak Performance from Your Fans

As the temperatures begin to climb, one of your top priorities should be ensuring your ventilation and cooling systems are in prime condition. Clean, well-maintained equipment plays a pivotal role in helping you battle the heat.
The fact that fans can function at drastically reduced efficiency is disturbing. Do you know that when they have worn-out belts, clogged louvers, or rust, performance is just around 20–60% of their stated capacity.
On the other side of the spectrum, sprinkler systems also require a thorough inspection. Ensure that every nozzle functions as it should and that there are no trace of leaks. Another important factor to check is the sprinkler timers. Check that areas are not over-saturated and that there is enough evaporation time.
In essence, a top-tier ventilation system combined with effective cooling measures serves as a protective shield. It helps cows steer clear of heat stress. You can rest assured that your bovine friends can continue their milk production even during those scorching days.

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