Dairy Heat Stress

Keep Animals Safe and Healthy During Excessive Heat

Thu, 24 Jul 2025 20:11:47 GMT

Excessive heat will once again blast much of the U.S. this week, with heat indices predicted to reach 110 degrees Fahrenheit or more in many locations. University of Illinois Urbana-Champaign animal welfare expert Angela Green-Miller says pets and livestock are at risk, and it’s up to humans to keep them safe.

Green-Miller runs the Animal Welfare, Environment, and Sustainability Laboratory as an associate professor in the Department of Agricultural and Biological Engineering, part of the College of Agricultural, Consumer and Environmental Sciences and The Grainger College of Engineering at Illinois.

Green-Miller answers common questions from pet owners and livestock producers.

First of all, how do animals cool themselves?
Different animals use different methods, but some broad brush-strokes for all animals include seeking shade and shelter, lowering activity and feed intake to keep metabolism down, and drinking more water. Any of the cooling strategies we would use, they would use too.

Don’t some animals not sweat? How do they keep cool?
That’s true. Dogs and pigs, for example. They dissipate heat through panting, defecation, and urination. They may increase those activities, which makes it that much more important to replenish their water supply.

What can humans do to help animals when it’s hot? Let’s start with pets.
Anything you would do for yourself, you could do for them. Bring them into the air conditioning, if possible, make sure they have access to plenty of water, and try to have them rest indoors or in the shade during the hottest part of the day. For outdoor animals, shade is critically important. Also, if they can be elevated from hot surfaces, such as on an elevated bed, that will let air circulate around them and remove some of that heat.

What about livestock?
We need to make sure the air is moving, bringing fresh air into the barn, even if it’s hot outside. The animals are contributing energy and heat into the environment, so the more of that we can move out, the better. And moving air over their body surface helps them release some of that energy.

For animals in indoor confinement, producers can alter lighting and feeding schedules. The idea is for them to rest during the hottest part of the day, so keep the lights down and withhold feed until it starts to cool down. That’s not an uncommon strategy, but there may be some producers out there who could use a reminder.

It’s also critical to ensure that water lines are working and that there’s fresh water flowing. Double-check those drinkers a little more frequently to make sure they’re not clogged. This is the time of year when we emphasize the critical nature of maintenance. If there’s any deferred maintenance, bump it up to the top of the priority list because a broken fan in this type of weather is one of the worst situations we can have.

What are the potential economic impacts of excessive heat on the livestock industry? Are there predictable dips in productivity every summer?
Absolutely. Feed intake is reduced during heat events, so we see dips in productivity. They’re also losing energy in the form of heat instead of putting it toward growth. We see reproductive impacts as well. Breeding rates tend to drop whenever there’s a heat event, and sometimes we see gestational impacts as well, especially in animals that are late in gestation.

Stop the Summer Surge: How to Keep Your SCC in Check

Mon, 16 Jun 2025 19:51:20 GMT

When temperatures climb and humidity hangs in the air, somatic cell counts (SCC) often follow suit. The added stress of hot weather can weaken a cow’s immune defense, opening the door for mastitis and setting the stage for SCC levels to spike.

While you can’t control the weather, you can take control of the situation. Amber Yutzy, assistant director of animal system programs at Penn State, and Emily Krekelberg, extension educator at the University of Minnesota, share practical strategies to help keep SCC levels in check all summer long.

Heat Stress Headaches
“Somatic cell counts tend to rise with temperature and humidity levels during summer,” Yutzy says. “Environmental stress caused by the high summer temperatures are responsible for the elevated counts. These higher somatic cell counts can stick around on your farm for weeks or months.”

Yutzy explains cows are simply more vulnerable when the heat sets in.

“We often see decreased production during hot weather because cows spend more time standing or lying where it’s cooler and less time eating at the bunk,” she says. “Environmental mastitis also increases during this time because of more frequent exposure of the teat end to bacteria.”

Add stress to the mix, and the immune system takes a hit.

“Research has shown high circulating levels of stress hormones interfere with the ability of the immune system to destroy bacteria. When bacteria enters the udder, the cow’s immune response sends somatic cells to fight back. But stress hormones depress the function of those cells — weakening the defense against mastitis-causing organisms.”

Even only a few problem cows can skew your bulk tank.

“Just a few cows with really high individual SCC can raise the entire bulk tank level,” Krekelberg adds. “Be sure to look at individual cow reports. This can help you pinpoint problem cows and potentially make culling decisions.”

Start with Cultures: Identify the Source
If your SCC is climbing, the first step is to identify the cause. That means culturing.

“Start with a bulk tank culture to find out if the problem is environmental, contagious or something else,” Krekelberg recommends.

Results will guide your strategy, but it’s best to test on multiple days. Sometimes, one aggressive organism overwhelms the plate and hides others. For a clearer picture, consider culturing individual cows with persistent high SCCs or new infections.

When It’s Contagious: Contain and Control
If the culture reveals contagious culprits like Staph aureus, Strep ag, or mycoplasma, you’ll need to implement aggressive containment.

“Contagious cows should always be milked last to avoid spreading the organisms to uninfected cows,” Krekelberg notes.

Krekelberg also advises housing infected cows separately and ensuring proper teat dip coverage, both pre- and post-milking.

“Pre-dip should have a contact time of at least 30 seconds with the teat skin surface,” she says. “Post-dip must fully cover the teat.”

She also stresses not overlooking the basics. Take time to assess how your milking equipment is functioning and review your cow prep protocol with employees. Regular inspections of liners, hoses and vacuum levels are essential to ensure optimal performance and prevent contamination.

When It’s Environmental: Clean, Dry, Repeat
If your issue is environmental, the goal becomes eliminating moisture and bacteria from the cow’s surroundings.

“Add more bedding to stalls or packs and change bedding more often,” Krekelberg suggests. “It could be worth it to bed twice a day if you notice cows are really getting wet and dirty.”

She also stresses keeping milking equipment clean and ensuring spotless teats before unit attachment.

“There should not be any dirt or manure present. Taking the time to clean teats thoroughly makes a huge difference.”

7 Steps to Help Lower Your SCC This Summer
Yutzy, along with British dairy vet Peter Edmondson, a mastitis and milk quality expert and owner of UdderWise Ltd., outline seven tactical steps to improve SCC — especially during high-risk seasons like summer:

Keep bedding clean and dry. Humid summer air encourages bacterial growth. Maintain clean, dry stalls to limit bacterial exposure and encourage cows to lie down in stalls rather than in manure-laden alleys.
Use fans and sprinklers wisely. While cow cooling is crucial, mismanaged fans or sprinklers can backfire by creating wet stalls, overly damp cows or congregation zones that collect manure. Aim to cool cows without compromising cleanliness.
Control flies aggressively. Biting flies are more than just a nuisance —they’re stress-inducing vectors for mastitis-causing bacteria. A solid fly control program protects both herd health and productivity.
Train the team. Reinforce milking protocols with all employees. Proper technique helps limit new infections and ensures early detection of clinical mastitis cases.
Provide plenty of fresh, clean water. At 80°F, cows drink up to 50% more than they do at 40°F. Adequate water access is critical to help them cool themselves through increased respiration and perspiration.
Stop the spread. Create a separate milking group for high-SCC cows and always milk them last. Use gloves and keep them clean. Whether you use paper or cloth towels, one per cow is the rule — no sharing. Replace cloth towels after 500 to 600 uses, and wash at high temperatures.
Make a plan and track it. Edmondson stresses the importance of clear, measurable goals. Focus on cows contributing the most somatic cells to the bulk tank. Consider their history, production and treatment response. Don’t rush to cull. Instead, evaluate carefully with your vet. Most importantly, monitor progress monthly.

Stay Low on Purpose
Keeping somatic cell counts in check through the summer heat takes more than just good intentions. It requires a combination of sound management, consistent routines and close monitoring. By staying proactive and focused on the details, you can limit seasonal setbacks and protect your farm’s milk quality all year long.

“Having a low SCC never happens by accident,” Edmondson concludes. “It’s the result of high intention, sincere effort, intelligent direction and skillful execution.”

Your Next Read: Improving Calf Health Starts with Better Prepartum Cow Nutrition

Calves Prefer Their Pals, Even in the Heat

Fri, 06 Jun 2025 17:00:00 GMT

The effects of heat stress on calves has been the topic of a good share of research in recent years. So, too, has been the study of social versus individual calf housing. Now, University of Wisconsin researchers have published a first-of-its kind study that examined the two factors together.

The research project, published in the Journal of Dairy Science , studied the behavior and physiological characteristics of pair-housed preweaned calves as they navigated competing motivations for social contact and thermal comfort.

A total of 50 Holstein heifer calves were housed in 25 pairs in adjoining hutches with a common outdoor run. In each pair of hutches, one was ventilated with 2 open windows at the rear base and the rear bedding door propped open. The other hutch had no ventilation.

Calves were exposed to and evaluated under 4 conditions for 1 daytime hour each – individually or in pairs confined to a ventilated or non-ventilated hutch. The experiment took place from later spring to fall.

The observations were conducted on 2 consecutive days during weeks 4, 6, and 9 of life. Immediately before and after the hutch confinement, respiration rate and rectal temperature were recorded while calves were outside.

On the subsequent third day in the test weeks, the location of each calf was recorded in 15-minute intervals using time-lapse cameras. They were able to move freely among the two hutches and outdoor run without confinement.

Findings included:

Calves had no hutch preference in week 4 of life, but significantly preferred the ventilated hutch in week 6 and 9 of life.
The temperature-humidity index (THI) within the ventilated hutches remained constant throughout the study, regardless of the number of calves in them. The unventilated hutches saw a rise in THI when calves were confined inside, which became more pronounced with 2 calves versus 1, and as the calves aged, grew larger, and began ruminating.
Not only did ventilation mitigate THI increase, but it also produced a significant reduction in respiration rate of calves when they were confined inside. The greatest reduction in respiration rate was observed in paired calves in week 6. Respiration rate inside and outside the hutch remained relatively the same for the non-ventilated hutches for calves of all ages.
No significant effect on rectal temperature was observed under any of the conditions.
Regardless of location, calves in the unconfined portion of the study preferred being together about 80% of the time.

The preference for staying together was true even inside the unventilated hutches. The researchers cited previous research indicating that calves have a strong desire to access and maintain physical contact with another calf.

They speculated that, when considering social contact versus physical comfort, calves were willing to endure higher temperatures and potentially poorer air quality to be with their partner.Even though evidence in the study indicated the ventilated hutches were more comfortable, calves were willing to forego that comfort to stay with another calf.

Your Next Read: The Hidden Cost of Heat Stress on the Unborn Calf

The Hidden Cost of Heat Stress on the Unborn Calf

Mon, 02 Jun 2025 15:05:00 GMT

As thermometers start to boil, dairy producers often turn their attention to the cows who are paying the bills: the lactating herd. But research shows that dry cows and bred heifers are just as vulnerable to heat stress, even if the signs are less visible.

While it’s easy to overlook this group of animals during the hustle and bustle of summer, doing so can quietly set off a chain reaction. When a dry cow or bred heifer experiences heat stress, her unborn calf does too.

Carly Becker, a former dairy extension educator for Pennsylvania State University, and Bethany Dado-Senn, a calf and heifer technical specialist at VitaPlus, weigh in with practical advice and insights on why cooling dry cows matters more than ever.

Lifelong Consequences for Calves

Numerous studies have shown that the effects of in-utero heat stress can be severe, starting at birth and continuing throughout a calf’s life.

“Calves born from dams under heat stress are basically doomed from the start,” Dado-Senn says. “They’re born smaller, have smaller mammary glands and are more likely to leave the herd due to either fertility or health issues. If they are fortunate enough to make it to the lactating herd, they’re going to make less milk across three lactations.”

That means the heat of one summer can ripple through a herd’s productivity for years.

Becker explains that these calves often face reduced placental function, are typically born about 8.8 lbs. lighter and struggle with compromised immunity due to failed colostrum transfer.

“Late gestation is a time when the fetus gains 60% of its birth weight,” she says. “If the dam is under heat stress, that calf is growing in a nutrient-restricted environment. Plus, these calves are often born early, which can further lower their chances of thriving.”

Unfortunately, the setbacks don’t stop there. In-utero heat-stressed calves have been shown to consume less feed, require more tube feedings and experience delayed growth well into their first year — all of which increase the cost to raise them and delay first calving.

The long-term impact can even extend into future generations.

“We know that this is a transgenerational problem as well,” Dado-Senn says. “The granddaughters born from calves who experienced heat stress in utero will also make less milk and have impaired mammary development. This severe stress can perpetuate across three to six lactation cycles and really get us off on the wrong foot.”

The Case for Cooling Dry Cows and Bred Heifers

While the lactating herd often gets the fans, misters and extra attention, dry cows and bred heifers need cooling just as much, especially those in the final weeks of gestation. Shade, ventilation and water access are baseline necessities, but sprinklers or soakers and tunnel ventilation systems in dry pens can pay big dividends.

“The dry period is a critical 45- to 60-day window,” Becker explains. “It’s when the cow is regenerating her mammary tissue, maintaining body condition and growing her calf. Yet too often, dry cows are left in less-ventilated barns or out in lots with little to no cooling.”

That oversight comes with a cost. Research shows heat-stressed dry cows produce 6.6 to 16.5 lbs. less milk per day in the following lactation and often face more health challenges after calving.

To help combat heat stress in dry cows and bred heifers, consider the following strategies:

Install and maintain fans or tunnel ventilation in dry pens and holding areas to keep air moving.
Use sprinklers or soakers on timers during peak heat hours to help cows dissipate heat effectively.
Provide ample shade, especially for animals housed outdoors. Natural tree lines, shade cloths or roofed shelters can offer relief.
Ensure unrestricted access to clean, fresh water. As temperatures rise, so does a cow’s water demand — sometimes doubling intake on the hottest days.
Manage stocking density to reduce crowding, which increases heat load and reduces airflow around animals.
Feed during the cooler parts of the day, like early morning or late evening, to encourage dry matter intake and minimize heat-related feed refusals.

Nutrition Plays a Role, Too

In addition to physical cooling strategies, nutrition can offer another line of defense against the effects of in-utero heat stress. According to Dado-Senn, one nutritional tool gaining traction is the use of rumen-protected methionine during late gestation. Methionine, an essential amino acid, is often the first limiting nutrient in dairy rations, especially during periods of heat stress when cows’ metabolic demands shift.

“Methionine supports the cow’s metabolism, reproductive function and immune health, but it also has direct benefits for the unborn calf,” Dado-Senn says. “Calves born to dams fed rumen-protected methionine often exhibit better growth, improved feed efficiency and enhanced energy metabolism. We also see developmental advantages like stronger intestinal growth, more favorable DNA methylation patterns and improved resilience to stress after birth.”

This can be particularly valuable when heat stress cannot be fully avoided. “For example,” she adds, “if a dam experiences heat stress but is supplemented with methionine, her calf may still be born with better thermal regulation and stronger postnatal growth.”

Rumen-protected choline is another promising nutritional intervention with similar benefits.

“When supplemented during late gestation, choline has been shown to improve calf growth, feed efficiency, and circulating metabolites,” Dado-Senn says. “In one study that included both beef and dairy calves, increased maternal choline intake, particularly in beef bull calves, was associated with higher weaning weights and better feed efficiency.”

While no nutritional strategy can replace the need for adequate cooling, these tools offer added insurance to help ensure calves are born with a stronger start.

Help Eliminate Heat Stress’s Silent Toll

Though heat stress during the dry period can often go unnoticed, its hidden costs run deep. Calves developing in heat-stressed dams typical arrive smaller and weaker, carrying challenges with them from birth that slow growth, delay breeding and reduce milk production over their lifetime.

Cooling with fans, shade and fresh water are easy ways to help minimize discomfort, yet nutrition can play a powerful role as well.

As Becker emphasizes, “Investing in dry cow and bred heifer cooling isn’t just about comfort. It’s about protecting your future herd and setting calves up for success.”

Your Next Read: 4 Tips to Reduce Fetch Cows in Robotic Milking Systems

Improving Calf Health Starts with Better Prepartum Cow Nutrition

Mon, 02 Jun 2025 14:55:47 GMT

Before a calf takes its first breath, its future is already being shaped. Research shows that what a cow eats and the stress she experiences during pregnancy can have a lasting impact on her calf’s development. From muscle growth and fat deposition to immune strength and future milk production, the prenatal environment a calf is developed in plays a big role in its long-term health.

“Nutritional decisions we make for the dam don’t just affect her; they directly impact the calf she’s carrying,” says Billy Brown, Extension specialist with Kansas State University. “We now understand that feeding and managing cows during gestation is one of the most powerful tools we have to influence the performance of the next generation.”

Programming a Calf’s Potential in the Womb

Brown points to a growing body of evidence suggesting the in-utero environment, especially during mid- and late-gestation, plays a critical role in shaping key systems in the developing fetus.

“In mid-gestation, that fetus is laying down muscle tissue. Then during late-gestation and early life after birth, fat tissue deposition begins,” Brown explains. “So, depending on when we provide nutrition or experience environmental stress, we can influence how those tissues develop.”

He notes these early-life impacts can affect growth, feed efficiency, disease resistance and even milk production in future lactations.

“We have seen this clearly in beef cattle, and it is becoming more evident in dairy calves as well,” he says.

Nutrition That Reaches the Next Generation

While it’s no secret feeding the dry cow well pays dividends in her own health and performance, research shows specific nutrients in late-gestation can directly benefit the calf she’s carrying.

“Methionine is a great example,” says Bethany Dado-Senn, calf and heifer technical specialist with Vita Plus. “A lot of producers are already feeding rumen-protected methionine to support milk protein synthesis, reproductive performance and overall metabolism. But if we include it in the dry cow diet, we now know that the calf benefits, too.”

According to Dado-Senn, calves born to methionine-supplemented dams show improved growth, feed efficiency and energy metabolism. On a cellular level, they also exhibit improved intestinal development and DNA methylation, which can help them better tolerate stress conditions.

“So, for example, if a dam is exposed to heat stress but is also provided methionine, her calf is likely to have improved thermal regulation and better postnatal growth,” she explains.

She adds that rumen-protected choline (RPC) offers nearly identical benefits. While traditionally fed to improve transition cow metabolism and reduce fatty liver, new research is showing it might also benefit the next generation.

“We see improved calf growth, stronger feed efficiency and changes in circulating metabolites,” says Dado-Senn. “In one study, beef bull calves born to choline-supplemented dams had significantly heavier weaning weights.”

RPC might also impact colostrum production.

“One study found that rumen-protected choline nearly doubled colostrum yield,” she notes. “That needs to be validated further, but we all know how much difference an extra liter or two of colostrum can make.”

Brown adds that on-farm economics make these additives worth a closer look.

“At our K-State dairy, RPC costs about 36¢ per cow per day,” he says. “We feed it for about three weeks prepartum, so it’s about a $7.50 investment. And we’re seeing not just better energy-corrected milk, but interesting calf outcomes too.”

Other dry cow ration strategies, such as feeding direct-fed microbials or managing dietary cation-anion difference (DCAD), are also being evaluated for their maternal-fetal benefits. For instance, extended feeding of more negative DCAD diets could support early-life metabolic programming and better calf growth.

Cooling and Comfort: More Than a Cow Benefit

Environmental stress during pregnancy can also leave a lasting mark. While most dairy producers view heat stress through the lens of lost milk, the impact on the unborn calf can be just as damaging.

“Calves born to heat-stressed dams are often smaller, have less-developed immune organs and struggle to achieve passive transfer,” Brown says. “They’re more likely to leave the herd early, and, if they do reach the milking string, they produce less milk over their lifetime.”

Brown notes that University of Wisconsin research led by Jimena Laporta found that cooling dry cows can add between 4.4 lb. and 14 lb. of milk per day across a daughter’s first three lactations. In addition, those daughters stayed in the herd nearly 300 days longer, on average.

“That’s practically a whole lactation added just by cooling the dry cow,” Brown says.

Prebirth Stress, Postbirth Impact

The relationship between dam health and calf resilience is becoming clearer with each study. Dado-Senn says elevated inflammation or oxidative stress in the dam around calving can result in calves with lower birth weights, increased markers of stress and inflammation, and higher risk of morbidity or mortality.

“We see it in the research, but we also see it on farms,” she says. “Calves born to transition cows that had issues like mastitis, metritis or ketosis are more likely to be treated multiple times or to have severe cases of scours.”

Even when cows show no clinical signs, subclinical inflammation can still affect the calf. For example, cows dried off with high somatic cell counts (SCC) produce colostrum with higher SCC and lower immunoglobulin levels, but studies suggest there’s more to the story.

“In one study, researchers fed colostrum from high-SCC cows to unrelated calves and saw no difference in serum proteins,” Dado-Senn explains. “But when calves were actually born to those high-SCC cows, their ability to absorb immunoglobulins was lower, even when fed good-quality colostrum. That points to a biological signal, an in-utero communication, that is already shaping that calf’s immune system before it’s born.”

Weighing the Investment

While data continues to highlight the far-reaching influence of maternal nutrition and stress, Brown reminds producers to balance innovation with economics.

“If you put pencil to paper, a lot of these practices, whether it’s cooling cows or supplementing with methionine and choline, are beginning to look like smart long-term investments,” he says. “They’re not just good for the cow. They’re good for the calf and for the sustainability of the herd overall.”

Your Next Read: 5 Must-Do Steps for Raising Healthy Beef-on-Dairy Calves Before They Leave the Farm

The Effects of Heat Stress on Dairy Cattle Development, Health and Performance

Tue, 22 Apr 2025 22:08:39 GMT

It is not breaking news that yearly temperatures on Earth have been consistently rising. Indeed, data released from NASA’s Goddard Institute for Space Studies – GISS show that the global land-ocean temperature index has consistently increased after the 1900s (see Figure 1 below).

Regardless of the many factors that have been tied to the increase in global temperature (some that were addressed in previous WSU VetMed Extension Articles ), it is evident that the agriculture is affected by such changes, including the dairy industry. With increased global temperatures, the occurrence of heat stress (a condition that occurs when the body is exposed to excessive heat, leading to an inability to regulate body temperature effectively) and its associated detrimental impacts are more likely to be observed particularly in dairy cattle.

A recent study projected the decadal increases in average heat stress frequencies by 2100, and revealed that the majority of the U.S. regions will have at least 6 to 8 additional days under heat stress/decade until 2100 ( Gunn et al., 2019 ; Figure 2).

Because of the expected differences in climate, it is important that dairy industry stakeholders work together to further 1) understand the complexity and underlying mechanisms of heat stress impacts, and 2) develop alternative strategies to mitigate the detrimental impacts of heat stress.

With that in mind, this article focuses on reviewing some of the key aspects related to heat stress impacts on cattle development, health and performance, industry economics, and mitigating strategies.

Historically, the temperature-humidity index (THI) has been the mechanism used to determine when dairy cows are heat stressed. Although there is some variation on THI cut-offs the consensus was established as a THI between 68 and 70 ( Zimbelman et al., 2009 ; Chen et al., 2024 ). Guinn et al. ( 2019 ) described the differences in mean THI between summer and winter months in the U.S. for the last 10 years (69.5 vs. 39.3, respectively), highlighting that without any heat stress abatement strategies U.S. dairy cows could be under heat stress conditions for most of the summer months.

In fact, the same study revealed differences in productive and reproductive performance between summer and winter, illustrated by reduced milk production and pregnancy rates in summer compared with winter months. Similar results were also reported by other authors, including lowered pregnancy rates in warmer months compared with colder months of the year ( Hansen, 2009 ). Both Tao et al. ( 2020 ) and Ouellet et al. ( 2020 ) depicted the detrimental impacts of heat stress on milk production and dry-matter intake (Figures 3 and 4).

Other studies have demonstrated the effects of heat stress (or contrast between warmer vs. cooler months) on the occurrence of diseases, culling, and cow welfare. For instance, cows that calved in warmer months were observed to have greater odds of retained fetal membrane (Odds Ratio = 1.6), subclinical ketosis (Odds Ratio = 2.3), displaced abomasum (Odds Ratio = 1.8), and mastitis (Odds Ratio = 1.1) as compared with cows that calved in cooler months ( Pinedo et al., 2020 ).

Al-Qaisi et al. ( 2020 ) observed a greater somatic cell count in milk from cows exposed to heat stress conditions as compared with cows exposed to thermoneutral conditions, and cows that calved in the summer were more likely develop metritis as compared to cows that calved in cooler months ( Molinari et al., 2022 ). Furthermore, Vitali et al. ( 2015 ) reported higher mortality of cattle during heat wave periods compared to subsequent periods, and an association of mortality and heat wave duration (Figure 5). Heat stress conditions have also been associated with welfare issues in dairy cattle, as cows under heat stress conditions remain in a standing position for greater periods of time (possibly contributing to lameness issues) and have greater blood cortisol levels than cows under thermoneutral conditions ( Cook et al., 2007 ; Allen et al., 2015 ; Al-Qaisi et al., 2020 ).

Considering the effects of heat stress on cattle performance, mortality, and welfare, it is not a surprise that economic losses occur. Specifically, data published in 2003 estimated that heat stress conditions cause up to $2.3 billion/year in economic losses to livestock production ($2.9 billion in 2024 considering inflation). Under heat stress abatement strategies, the economic losses drop down to $1.7 billion/year and the dairy industry represents over 50% of the costs ($897 million; St-Pierre et al., 2003 ).

A component to heat stress in dairy cattle that has received a lot of attention is the “in utero” heat stress on dairy calves. Recent studies highlighted the carryover effects of late gestational heat stress on the progeny, illustrated by lowered birth weight (-4.6 kg), lowered weaning weight (-7.1 kg), and reduced longevity ( Ouellet et al., 2020 ). Moreover, the occurrence of heat stress during the dry period is also associated with differences in offspring mammary gland structure ( Dado-Senn et al., 2019 ), adrenal gland development ( Guadagnin et al., 2024 ), behavior ( Laporta et al., 2017 ), and hormonal/metabolic biomarkers ( Guo et al., 2016 ).

Lastly, combined studies have shown the legacy effect of heat stress on offspring, as lactational performance of such offspring is also different compared to offspring generated by dams under thermoneutral conditions ( Ouellet et al., 2020 ; Figure 6).

The research findings related to the legacy effect of heat stress on offspring add another layer of importance to the topic, and suggest that the detrimental effects and economic losses previously described are potentially underestimated.

Although the complex mechanisms that underlie the detrimental effects of heat stress on lactating dairy cows are not yet fully elucidated, studies have demonstrated biological changes associated with heat stress. For instance, lipopolysaccharide-induced accumulation of IL-1β, IL-10, and MIP-1α was greater in blood collected from postpartum cows that were under prepartum heat stress conditions as compared with control cows,implying that prepartum heat stress has carry-over effects on postpartum innate immunity, which may contribute to the increased incidence of uterine disease observed in cows exposed to prepartum heat stress ( Molinari et al., 2023 ).

Other studies have depicted differences in gut, ovary, muscle, and metabolism morphology/function associated with heat stress, which could be tied to the occurrence of subsequent diseases, animal performance, reproductive performance, and mortality ( Baumgard and Rhoads Jr, 2013 ; Fernandez et al., 2015 ; Hale et al., 2017 ; Ross et al., 2017 ; Fausnacht et al., 2020 ; Mayorga et al., 2020 ; Tang et al., 2022 ; Roths et al., 2023 ). Last but certainly not least, and certainly not depicting the entirety of the mechanisms of heat stress associated with cow performance, cows under heat stress conditions have reduced feed intake ( Rhoads et al., 2009 ) and reduced energy substrate adaptability in skeletal muscle, possibly contributing to reduced performance ( Ellett et al., 2025 ).

Given the detrimental impacts of heat stress on cattle performance, health, and welfare, it is important to consider the region-specific variations in climate and implement heat abatement strategies as needed. There are a variety of heat abatement strategies available for dairy calves, heifers, and cows that can be implemented in dairy operations. Multiple studies have tested the effects of different strategies for heat abatement in calves.

For instance, Dado-Senn et al. ( 2020 ) reported a positive association between postnatal heat stress abatement and thermoregulatory responses, feed intake, and health in dairy calves. Montevecchio et al. ( 2022 ) reported a positive relationship between pre-weaning heat stress abatement and lying behavior and healing time (related to disbudding) in dairy calves. The same group also reported positive welfare-related responses and greater wither-height for calves given heat abatement strategies as compared to calves under a simple plywood hutch ( Montevecchio et al., 2022 ).

Benefits for heat abatement in heifers and cows were also reported. For instance, the use of shade from a freestall barn, water soakers, and fans were associated with positive effects on heifer thermoregulation and productivity as compared with heifers kept under freestall shade only ( Davidson et al., 2021 ). Gunn et al. ( 2019 ) described the milk production losses (per cow/year) according to different heat abatement strategies, ranging from minimal (open barn or shading) to intense (air conditioning).

Aside from structural tools to improve heat abatement for dairy cattle, other studies have reported varying results associated with nutritional tools to ameliorate the impacts of heat stress in dairy cows, including chromium supplementation ( Soltan, 2010 ), Saccharomyces cerevisiae supplementation ( Al-Qaisi et al., 2020 ), choline ( Holdorf and White, 2020 ), and other components ( Fabris et al., 2017 ).

The potential of other strategies for heat abatement have been described; for example, a research group from the University of Florida reported that the SLICK haplotype confers thermotolerance in intensively managed lactating Holstein cows ( Dikmen et al., 2014 ). In that study, the authors revealed that cows carrying the SLICK haplotype had lowered rectal temperature and respiration rate across most times of the day compared with cows not carrying the SLICK haplotype.

Although several aspects associated with the SLICK haplotype have not been explored, a recent study reported that SLICK Holstein cows in Puerto Rico exhibited lower body temperatures, greater voluntary solar radiation exposure, enhanced blood supply to the mammary gland, and alterations in genes and metabolites involved in arachidonic acid metabolism at the mammary gland and blood plasma ( Contreras-Correa et al., 2024 ).

Figure 1

(The Author)

Figure 1. Global land-ocean temperature index ( NASA’s Goddard Institute for Space Studies – GISS ).

(The Author)

Figure 2. Projected decadal increases in average annual Heat Stress Frequency between 2000 to 2100 ( Adapted from Gunn et al., 2019 ).

Average Daily THI

(The Author)

Figure 3. Correlation between milk yield and the average daily temperature-humidity index (THI) of the previous week. Circles represent individual observations, and dash line represents simple linear regression. All cows were housed in the same barn equipped with evaporative cooling, and fed similar lactating cow rations (Adapted from Tao et al., 2020 ).

(The Author)

Figure 4. (A) Summary of difference (kg/d) in milk yield in late-gestation heat-stressed cows relative to cooled counterparts (average difference = 3.6 kg/d; 10.3%) and (B) difference (kg/d) in prepartum and postpartum dry matter intakes in late-gestation heat-stressed cows relative to cooled counterparts (prepartum average difference = 1.4 kg/d; 12.7%; postpartum difference = 0.1 kg/d, 0.5%). Adapted from Ouellet et al., 2020 .

(The Author)

Figure 5. (A) Odds ratio and 95% CI calculated for dairy cow mortality during heat wave (HW) and in the 3 not heat wave days (nHW) after the end of heat wave (d 1, 2, and 3 defined as nHWst, nHWnd, and nHWrd, respectively). (B) Odds ratio and 95% CI calculated for dairy cow mortality in relation to the duration of exposure to heat. The duration of exposure was classified as short (1 to 3 heat wave days), medium (4 to 6 heat wave days), long (7 to 10 heat wave days), and very long (>11 heat wave days). Odds ratios are statistically significant when 95% CI does not include the unit (dashed line). Adapted from Vitali et al., 2015 .

(The Author)

Figure 6. Summary of the performance impairments associated with late-gestation heat stress for the dam (1), daughters (F1), granddaughters (F2), and dairy sector (2) reported in a series of study (where ECM = energy corrected milk). Extracted from Ouellet et al., 2020

Cool Calves Live Longer

Thu, 03 Apr 2025 19:18:50 GMT

The average number of lactations of a U.S. dairy cow currently rests at about 2.8, or around 5 years of age.

That’s a fairly shocking statistic, considering a cow’s natural lifespan can be up to 20 years or more. And, on average, it takes about two full lactations before heifers begin to generate return on investment for their rearing or purchase cost. Given today’s robust heifer values, that time before young cows begin to pay the bills may be even greater.

So, how can we help cows live longer, more productive lives? Researchers at the University of Florida assessed one factor: birth season. They predicted that cows that entered the world during seasons of heat stress would have shorter lifespans. And they were right.

The study, led by researcher Izabella Toledo and published in the Journal of Dairy Science , examined the DairyComp records of more than 10,000 cows in Florida and 8,000 in California that remained alive and productive for more than 5 lactations.

The data were sorted to identify animals born over a period of 10 years (2012-2022) in the cool season (December, January, February, and March) and the hot season (June, July, August, and September). Cows born in the more temperate months of April, May, October, and November were not included in the dataset.

In Florida, 14.5% of cows (1,567) born in the test months were still alive and milking after 5 lactations. Of them, more than double (1,129, or 72%) were born in the cool months compared to the hot months (438, or 28%). In California, 20.4% (1,669) of the dataset made it 5 lactations or longer, with 56.% of them born in the cool months, versus 44% born in the hot months.

The Florida dataset also was analyzed for the number of cows born in the tests months that were dead or sold for beef in the first 4 lactations, and the reasons why. A total of 1,454 were sold and another 238 died. Selling reasons included breeding, foot and leg, digestive, and respiratory issues, along with mastitis.

Significantly more cows born in the hot season (53%) compared to the cool season (47%) were sold for beef.On-farm deaths also were significantly higher for cows born in the hot (54%) versus cool (46%) season.

Toledo and her team concluded that the results give even more credence to the deleterious impacts of heat stress on dairy productivity. Previous studies – many also conducted by University of Florida researchers – have shown that heat stress during late pregnancy affects dams’ milk production in the next lactation, immune function, and calf birth weight.

Further, they have found that calves exposed to heat stress in late gestation had 19% lower milk production in their own first lactations, and even passed that lower milk production potential on to their offspring.

Toledo said the results of the current study suggest a potential two-pronged approach to protecting the productive life integrity of newborn heifers: (1) implement heat-stress abatement measures for dams, including shade, fans, soakers, and misters; and (2) alter breeding decisions to avoid births in seasons of peak heat.

Your Next Read: A New Kind of AI for Dairy Calves

The Five Cow Transportation Tips You Need to Know During Hot Weather

Mon, 17 Jun 2024 13:00:00 GMT

The scorching hot temperatures of summer have arrived. While it’s easy to crank up the A/C at home, it’s not so easy to keep cows cool and comfortable. Though dairy farmers have become much more efficient at mitigating heat stress, cows still need to be handled during the hottest days of the year. Thus, taking the time to conduct a quick refresher on animal handling during hot weather is a necessary practice for you and your team.

The Beef Quality Assurance guidelines suggest the following tips to help keep cattle cool and calm during the heat of the day.

Extreme heat conditions exist when the temperature and humidity are at levels in which they create a heat index greater than or equal to 100ºF. Heat index levels of 100ºF or greater pose a significant health risk to stressed cattle. Avoid transporting cattle in extreme heat conditions.
Avoid hauling and handling cattle between 11:00 am and 4:00 pm, which is most often the hottest time of the day. If cattle must be hauled at times of high temperature and humidity, avoid stopping. If stopping along the way is absolutely necessary. Make stop durations as short as possible.

Stop during cooler parts of the day, if possible.
Pick shaded areas to park if you have to stop.

3. Consider placing fewer cattle on the trailer during hot weather.

4. Handle cattle gently and patiently during extreme heat conditions. When cattle are stressed in extreme heat conditions, they are more likely to become non-ambulatory, sick, and possibly die.

Haul animals fit to transport. Fitness for transport is determined by multiple considerations including the health, mobility, and body condition score (BCS) of the animal. Do not transfer cattle with BCS score of less than 2 non-ambulatory animals or those with severe mobility issues and animals appearing exhausted, dehydrated, or otherwise health impaired.

Summer 2024 Predicted to Bring on the Heat

Mon, 29 Apr 2024 18:58:44 GMT

Bust out the sunscreen and cattle misters. It’s gonna be a hot one this summer if USDA meteorological predictions are correct.

Dr. Dennis Todey, Director of the USDA Midwest Climate Hub , shared on a recent webinar sponsored by the Iowa Farm Bureau Federation that current weather patterns are signaling excessive summer heat ahead.

He said the outlook for July, August, and September is for above-average temperatures in virtually the entire country. The areas showing the greatest likelihood for above-average temperatures are the western third of the country -- minus a band on the far west coast that includes most of California – and the upper New England states.

The precipitation outlook, on the other hand, is neutral, except for a two-to-three-states-deep region along the entire eastern seaboard, which models show having a likelihood of above-average precipitation.

Todey said there are strong signals that the U.S. is in a “rapid transition” between a strong “El Nino” weather pattern to an equally prominent “La Nina” pattern – a shift that will likely occur sometime between June and August 2024.

The current El Nino was short-lived, lasting only about a year, and followed 3 years of a La Nina pattern. El Nino patterns are typically associated with mild winters. This was certainly the case in 23-24, which posted near-record warmest winter temperatures in December, January, and February. The states with the most pronounced warmth compared to normal winter temps included North Dakota, Minnesota, Wisconsin, Michigan, New York, and the New England states up to Maine.

La Nina is the opposite counterpart of El Nino. In its most recent, 3-year stretch, it coincided with dry weather in a large part of the country. Todey said Iowa – the nation’s largest corn-producing state – has been in a consistent D1 (moderate) drought since July 2021, a record length for the USDA Drought Monitor.

As of the first week of April 2024, pockets of “Extreme” drought were noted by the Drought Monitor in Iowa, Montana, New Mexico, and Texas. Southeastern New Mexico also has an area of “Exceptional” drought, which is the highest categorization of drought status by the Drought Monitor.

“We can’t say for sure whether the next La Nina will perpetuate dry conditions, but there is also no strong indicator of precipitation,” noted Todey. “We will likely be very reliant on getting rainfalls at the right time through the summer.”

The meteorologist has observed an interesting shift in precipitation patterns that is affecting growing seasons. “In terms of temperatures, we’re seeing an increase in growing season length by about 10 days per decade,” he noted. “At the same time, there has been a 20-year trend of midsummer dryness, with more annual rainfall arriving in the spring.”

Coming out of a warm winter is affecting moisture levels on hand. Todey said the lack of frozen soils allowed moisture to absorb more readily – the good news. But the bad news is that warmer temps caused evapo-transpiration to occur at a higher rate. Essentially, the two factors cancelled each other out.

“Iowa is currently at ground-zero for driest soil conditions,” he declared. “While not as widespread, some of those conditions also exist in parts of Missouri and Kansas. It seems probable that we’ll need to preserve moisture this year.”

Looking toward the planting season and beyond, Todey offered the following advice:

Pull back on yield goals for crop projections and inputs. Lackluster soil moisture recovery could limit the effectiveness of fertilizer.
Plant as early as possible to take advantage of spring moisture.
Reduce tillage – every time you do a tillage pass, you lose moisture.
Closely monitor well and groundwater sources upon which you rely for livestock and/or irrigation, so you can proactively develop alternative plans if necessary.

The full webinar and additional comments from Todey can be viewed here .

For more on weather, read:

Facility Focus: Five Strategies to Reduce Calf Heat Stress

Mon, 29 Apr 2024 13:39:37 GMT

Excessive heat can take a toll on every animal on the farm – especially the lactating herd. But one group that’s typically overlooked when it comes to heat stress are often the youngest members of the herd.

“When we think of the effects the environment has on calves, cold stress is often the more common concern, especially in more temperate climates. However, soaring summer temperatures, hot sun, and high humidity can cause heat stress in calves and heifers just as in the milking herd,” said Coleen Jones and Jud Heinrichs, a former research associate and professor emeritus of dairy nutrition, respectfully, at Pennsylvania State University.

While calves are often better at coping with heat compared to their adult counterparts, it’s important to know what methods help combat heat stress. As temperatures begin to creep their way higher, the duo recommends the following five strategies to help keep calves cool and healthy during the heat of the summer.

Provide Shade – Just like sitting under a tree during the heat of the day, shade provides relief from direct sunlight, helping to prevent overheating. Studies have shown providing shade reduces the temperature inside hutches and lowers calf body temperature and respiration rate. Consider installing shade cloth above outdoor hutches to calves combat the heat.

Keep Air Moving – Even a slight breeze can help make a stifling day more bearable. When air moves across the skin, it helps carry away the heat your body generates. The same can be said for calves. According to the duo, calf housing should be positioned to utilize prevailing winds and should incorporate as many openings as possible to take advantage of natural air movement. Air movement can be enhanced by opening vents on hutches and placing a block under the back wall.

Keep ‘em Hydrated – With increased temperatures comes increased respiration. In turn, this can cause calves to become dehydrated more quickly. To combat this, be sure to offer clean water to calves early on. In addition, water buckets also may need to be filled more frequently in the summer, particularly for calves nearing weaning and those who have recently been weaned.

Make Sure Grain Stays Fresh – According to Jones and Heinrichs, calves will naturally tend to eat less grain during periods of heat stress. To keep calves eating, consider offering only small handfuls of started at each feeding until calves begin to eat. Remove uneaten starter and clean out wet or moldy feed daily to maintain freshness. A divider between the grain bucket and water bucket can help keep starter fresh longer by limiting the amount of transfer between the two buckets.

Work Calves in the Morning – Throughout the summer, the early morning hours are typically the coolest part of the day. To help reduce heat stress for both calves and employees, the Jones and Heinrichs recommend completing strenuous tasks during the early hours of the day.

“As with other classes of cattle, it is wise to handle calves in the morning so that stressful activities, such as dehorning, vaccinations, pen moves, or transportation, can be completed when both calf body temperatures and environmental temperatures are at their lowest point for the day,” the duo state.

For more Facility Focus stories, read:

VES-Artex Unveils New Cow Cooling Technology: Intelligent Soaker 2.0

Thu, 14 Mar 2024 21:43:10 GMT

While the weather has certainly been mild this winter, thermometers will soon begin to boil as summer temperatures make their way across the country. With the warmer temperatures comes the increased risk of heat stress, which can contribute to a wide array of health and production setbacks for dairy cattle.

To combat this, VES-Artex has recently unveiled a new soaking system, Intelligent Soaker 2.0, which is designed to help alleviate heat stress while significantly reducing water usage on dairy farms. The system utilizes intelligent sensor technology to spray water when a cow is present based on temperature setpoints.

VES-Artex says that key features of the Intelligent Soaker 2.0 include easy installation, compatibility with existing systems and durable stainless-steel nozzles. In addition, the system’s cow-friendly LED light indicator simplifies monitoring, signaling when units are active and when they are in dwell mode.

The Intelligent Soaker 2.0 behaves similarly to a traditional soaker with both on and off intervals. Upon sensing a cow, the unit will begin soaking for 45 seconds, then it will enter a dwell mode where it won’t soak, even if a new cow comes within its range for 5 minutes.

“The Intelligent Soaker 2.0 addresses the dual challenge of animal welfare and sustainability,” says Dr. Mario Mondaca, Senior Technical Applications and Research Engineer at VES-Artex. “By minimizing water waste, farms can achieve a more sustainable operation while providing much needed heat abatement for the herd.”

According to the company, the new technology can help reduce water usage by 50%-70% when compared to traditional soaking systems. Unlike conventional soakers that operate continuously even after temperature thresholds are met, the Intelligent Soaker 2.0 optimizes water usage by delivering targeted cooling precisely when and where it’s needed.

“If you look at how the cow spends her day, she is feeding and in the alleys around 28% of the time,” Dr. Mondaca says. “This is why we are seeing reductions close to 70% on some days when compared to a system running all day long on a timer.”

With water conservation becoming a key focus for many dairy producers, the high-tech soaking system could be a compelling solution to conserve water and increase sustainability all while maximizing cow cooling.

For more on Smart Farming, read:

How Will This Year’s Heat Stress Affect Future Offspring?

Fri, 08 Sep 2023 16:21:56 GMT

Whether you dairy in Texas, Minnesota, New York, California, or somewhere in between, it’s been one long, hot summer.

A growing body of research shows that heat stress not only affects cows. It also can impact the fetuses being carried by close-up dry cows. Two studies recently published in the Journal of Dairy Science explore the impact of heat stress on the babies-on-board of near-term cows, and possibly even the next generation.

Effects of heat stress on birth weight, and comparison of environmental versus genetic parameters. This German study evaluated data from 171,221 Holstein cows to assess the effects of heat stress on calf birthweight. Specifically, the researchers sought to determine whether phenotypic responses or genetic breeding for heat tolerance were transmitted more prominently via calf birth weight when dams were under heat stress in their last 8 weeks of pregnancy.

Prenatal heat stress – measured via daily temperature-humidity indices (THI) -- reduced calf birth weight by a range of .66 to 1.38 pounds per calf. The researchers concluded this decline in birth weight was most likely caused by maternal permanent environmental effects versus genetics.

As a result, they recommended that dry-cow cooling efforts are more important in protecting fetal growth than using genetic evaluations for heat tolerance. But they also noted that the overall impact of maternal heat stress on fetal birth weight was relatively small from a practical perspective.

Changes in skin and hair characteristics in offspring of heat-stressed dams. This study , conducted at the University of Wisconsin-Madison, looked at the influence of heat stress in the pregnant dam on skin and hair development of the offspring.

They noted that the fetal germline in the developing reproductive organs of the fetus (F1) will eventually give rise to the next generation (F2), and also experience heat-stress insult. Thus, heat stress has the potential to impact the dam (F0), the fetus she is carrying (F1), and the eventual offspring of that fetus (F2).

Looking specifically at hair and skin adaptations triggered by in-utero heat stress, the researchers noted that heat stress in the last 56 days of gestation did, indeed, influence skin and hair characteristics in the granddaughters of those dams. The F2 offspring of heat-stressed dams had shorter and thicker hair, thinner skin, and more but smaller sebaceous glands.

Similar skin and hair adaptations in other animals species have been shown to aid in dissipating heat from the skin’s surface. Whether the same effect will occur in cattle remains to be investigated.

Seven Tips to Help Calves Beat the Heat

Thu, 06 Jul 2023 13:23:56 GMT

It’s summertime, and the livin’ is easy – except not for calves, who suffer heat stress right along with their older herd mates.

While calves have a larger surface area relative to body weight, and don’t generate as much body heat as adult cows, they are at risk of heat stress, nonetheless. Calves’ smaller body mass and weight means they dehydrate more quickly than cows. Numerous studies also have shown that calves born in the summer have sub-par bodyweight gain compared to their peers born in cooler months. And their less-developed immune systems also make them more vulnerable to stress-related illnesses.

Here are five strategies to help mitigate heat stress and keep calves healthy and growing through the peak heat of summer:

Provide shade – Calves in hutches may have a hard time escaping heat, especially when outdoor temperatures are excessive, because they have a hard time finding relief either indoors or outdoors. Installing 80% shade cloth about 4 feet over hutches has been shown to reduce the interior hutch temperature by 3F and calf rectal temperature by 0.5F in an Alabama study.

Hutches also can be placed under natural shade from trees as an alternative. Calves housed in barns have natural shade, but be sure to watch for “hot spots” where they are not protected during certain times of the day. Installing and adjusting curtained sidewalls can help manage sun exposure in buildings.

Create airflow – University of Pennsylvania Dairy Extension educators Coleen Jones and Jud Heinrichs suggest that, typically, open-faced buildings should face southeast, and hutches can be positioned to face east in the summer to maximize air movement and minimize solar heating. Hutch vents should be opened, and Washington State University research has proven the merits of elevating the back of hutches with a concrete cinder block (7.9 inches high) to encourage airflow reduce calf respiration in hutches. Building ventilation systems will vary, but maximizing both natural and mechanical ventilation will help keep calves cool, improve air flow and quality, and reduce pathogen growth.

Water, water, water – Calves need water to maintain body temperature. In hot weather, they lose more water through increased respiration and sweating. Michigan State University Dairy Extension educator Cora Okkema said an Iowa State University study showed calves with continuous access to fresh, clean water starting at birth had better rumen development, improved nutrient digestibility, and higher growth rates compared to calves whose water accessibility was delayed to 17 days of life. Okkema noted that older calves can consume 2-3 gallons of water per day, so attention to water delivery throughout the day is important. Several suppliers also offer oral electrolyte products that are used ad-libitum in drinking water for preweaned calves under severe heat or transportation stress.

Keep grain fresh – Flies, mold, and heat spoilage all are greater challenges for feeding starter grain in the hotter months. But because calves also eat less grain when they are hot, it’s important to keep the grain supply as fresh and appealing as possible. Jones and Heinrichs suggested feeding just a few handfuls of grain until calves are eating it readily, and discarding uneaten portions. A divider between grain and water buckets – or complete separation between these two feedstuffs – will help prevent grain contamination and spoilage.

Use inorganic bedding – Many producers prefer sand bedding in the summer months to help keep calves cooler. Regardless of bedding used, it should be clean and dry to encourage calves to rest.

Bump up nutrients – Cold stress tends to get more attention than heat stress when it comes to adusting liquid rations. But calves need more energy to regulate their body temperatures in periods of heat stress, too. And, unlike wintertime when calves can eat more starter grain to partially fuel their increased energy needs, they are likely to eat less starter grain than normal in hot weather. That makes the liquid ration the more logical means of delivering more nutrients. This can be accomplished by adding an extra daily feeding, boosting solids, or feeding more of the standard ration at regular feeding times, on the advice of your herd nutritionist.

Adjust management practices – Jones and Heinrich suggested avoiding the heat of the day for tasks like dehorning, castration, vaccination, pen sorting, and transportation. All of these tasks are best performed early in the morning when both environmental temperatures and calf body temperatures are at their lowest point in the day.

Finally, Okkema advised to “take care of your caretakers.” She said, “The summer heat is hard on everyone. Tempers flare, patience is thin, people get tired more quickly, and the idea of taking shortcuts is all-too-appealing.”

She suggested keeping a refrigerator stocked with snacks and drinks, encouraging regular cooling breaks, and educating workers about the symptoms of heat exhaustion and heat stroke.

For more on calves and heat stress, read:

Bupleurum Extract – A Heat Stress Antidote?

Tue, 20 Jun 2023 21:18:18 GMT

A popular Chinese herbal supplement is being evaluated as a potential feed additive to mitigate the effects of heat stress in dairy cattle.

Bupleurum is a centuries-old herbal supplement used in Chinese human medicine. It is created from the root of the Bupleurum chinense plant by drying the roots and grinding them into powder.

Asian cultures have long embraced Bupleurum for its perceived liver-cleansing benefits and to treat fevers, colds, and flu. In more recent years, interest in Bupleurum has grown among Western consumers as a tool to support immune health, boost mood, and fight inflammation.

And now, the dairy cow is catching the Bupleurum wave, with interest in using it as a heat stress aid.

In addition to the obvious setbacks in milk production and dry-matter intake, heat stress has been implicated in previous studies in damaging cows’ immune systems; fueling metabolic diseases; changing their hematological (blood) parameters; and inciting disorders related to hormone levels in their serum, causing potential reproductive setbacks.

Changes in circulating water and minerals due to heat stress have also been shown to disrupt osmotic balance and disrupt blood-pressure regulation in cows.

A recent study published in the Italian Journal of Animal Science evaluated 40 lactating Holstein cows in a heat stress setting. Heat stress thresholds in the study were defined as a Temperature-Humidity Index (THI) of 72 and body temperature exceeding 102.2°F. Actual conditions in the three-month study were an average THI of 78.2, and average body temperature was 102.7°F.

Cows were divided into four feeding groups of 10 animals each. The control group received no Bupleurum supplement, while the other three groups received, respectively, powdered Bupleurum extract at 0.25, 0.50, and 1.0 grams/kilogram of dry matter.

In the study, the dose of 0.5 g/kg proved to be effective in improving the hematological parameters of heat-stressed cows. Specifically, those cows had higher red blood cell counts, hemoglobin, hematocrit, and white blood cell count, compared to the non-treated controls.

The 0.5 g/kg dose also decreased blood sodium concentrations and increased calcium and potassium concentrations, and lowered serum cortisol (stress hormone) levels.

Various benefits also were observed at the other dosage levels, and no deleterious effects were observed at any dosage. But the researchers concluded that 0.5 g/kg produced the most collectively beneficial outcomes of supplementing with Bupleurum to help cows cope systemically with heat stress.

For more on heat stress, read:

Beating the “Summer Slump”

Wed, 14 Jun 2023 19:14:11 GMT

When it comes to calf and heifer nutrition, heat stress deals a double whammy. The animals need to expend more energy for body heat regulation, while at the same time they don’t feel like eating, which reduces dry-matter intake.

A recent review published in the Journal of Animal Science and Biotechnology evaluated a large collection of studies on the impact of heat stress on dairy calves and heifers. Consistently, they showed:

Calves and heifers subjected to heat stress had lower feed intake, average daily gain (ADG), and feed efficiency, compared to animals in cool or neutral climate conditions.
Energy expenditure on maintenance and metabolism increases to remove body heat load.
Gastrointestinal motility decreases in the body’s attempt to reduce metabolic heat, so lower ruminal passage rates of feed have been observed.
Rumen microbiota and fermentation in older heifers also are affected by heat stress, with a shift in the balance of volatile fatty acids (VFAs), which provide the main energy supply for growing heifers.

Nutritional Strategies

The review authors suggested that, in addition to physical cooling strategies like shade and misters, and some select breeding strategies, nutritional alterations may help calves and heifers navigate heat stress without sacrificing gain. They include:

Increasing volume and nutrient density in liquid rations of preweaned calves, to compensate for the reduction in starter-grain intake during heat stress.
Increasing the ration nutrient density for older heifers. The authors proposed increasing dietary fat without reducing dietary fiber, because heifers still need fiber to ruminate and maintain health. They said added fat has been shown to improve the efficiency of converting dietary fat to body fat, producing less systemic body heat compared to digesting protein and carbohydrates.
Supplementing heifer rations with zinc and vitamins A, C, and E to help relieve oxidative damage due to heat stress.
Balancing heifer rations for dietary cation-anion difference (DCAD) to support electrolyte balance, help maintain the blood-acid base, and correct mineral deficiencies caused by loss of sodium and potassium due to sweating.

When should these nutritional strategies be deployed? Probably sooner than you think as the warm season approaches. The authors stated the thermoneutral zone of calves – beyond which they begin to feel heat stress – is between 55 and 77°F. For heifers gaining 1.8 lbs./day, it’s between 32 and 59°F.

For more on heat stress, read:

Gene Editing Could Improve Heat Tolerance

Mon, 12 Jun 2023 21:07:07 GMT

The detrimental health, well-being, and productivity effects of heat stress in dairy cattle could one day be partially solved through gene editing.

The currently experimental technology removes an undesirable genetic trait in an animal and replaces it with a more favorable one at the genome level, known among researchers and regulators as an “intentional genomic alteration” (IGA). It is possible to introduce traits within a species, and between species.

In the case of heat stress, two approaches are being taken by researchers to help cattle cope:

Slick hair coat gene – Some cattle have a shorter and shinier hair coat that makes them more comfortable in high-heat environments and thus less susceptible to heat stress. This unique hair coat is the result of the dominant “slick” gene, which originates from the Senepol breed.

A collaborative project between researchers at Mississippi State University and the University of Puerto Rico studied 84 Holsteins with the naturally occurring “slick” gene. They found that the animals had lower body temperatures, lower respiration rates, and improved reproductive efficiency in tropical conditions, compared to herd mates with traditional hair coats.

Using a technology called CRISPR-Cas9, researchers in many parts of the world, including the United Kingdom, New Zealand, and the U.S., have successfully produced cattle with the slick coat gene. Semen from some sires that are homozygous for the slick gene through conventional breeding also is currently available.

Hide color alteration – New Zealand researchers are exploring how gene editing can dilute the jet-black hide color of Holsteins to make them less susceptible to heat stress. They said black absorbs more solar radiation, contributing to heat stress.

In their study , they used gene editing to swap the black gene in Holsteins with the semi-dominant color dilution phenotype from Galloway and Highland cattle. The resulting calves carried a typical, spotted hide pattern, but instead of black, the darker pattern areas were a silvery gray color that would attract less heat.

Developers of gene-editing technology emphasize that the process simply takes traits already occurring in nature and shares them with other animals, thus exponentially accelerating genetic progress for that trait. In the case of heat stress, they emphasize environmental advantages along with animal health, comfort, and productivity.

Once an animal receives the IGA, it is passed on to future offspring, making it possible to replicate the trait via conventional breeding. In March 2022, the FDA approved the first IGA for animals intended for food production by making a “low-risk determination” for two genome-editing beef cattle created with the slick hair coat.

The FDA declared the animals and their offspring safe for human consumption. Acceligen , the company that developed the slick-coat cattle, is now free to market the cattle, their genetic material, and their offspring, without further regulatory approval.

But in the U.S., the commercial application of gene editing still is subject a case-by-case approval process. Dr. Steven Solomon, director of the FDA’s Center for Veterinary Medicine, said, “We expect that our decision will encourage other developers to bring animal biotechnology products forward for the FDA’s risk determination in this rapidly developing field, paving the way for animals containing low-risk IGAs to more efficiently reach the marketplace.”

For more on heat stress, read:

Pour Hydration to Heat-stressed Calves

Thu, 14 Jul 2022 20:42:00 GMT

When calves are born, their bodies are made up of about 80% water. As they grow, they need to consume about 10% of their bodyweight in water daily. Retaining a high level of water in their physiological make-up is critical, and cannot be done via milk or milk replacer feedings alone.

Penn State University researchers underscored the importance of water for calves in a recent publication . They said a 2019 study by Iowa State University researchers showed that the full water requirements of calves are typically not met because a sizable portion of calves are not offered free-choice water until about 17 days of age.

The researchers noted that offering supplemental drinking water starting at birth resulted in better growth performance and apparent total tract digestibility of nutrients. Offering water starting on day 1 of life also had improved rumen function, leading to improved growth and feed efficiency – an important consideration in today’s climate of high feed costs.

And in the heat of summer, even water alone may not be enough. Providing free-choice electrolytes, or adding a mid-day electrolyte feeding, is a growing practice among calf raisers in the United States.

New York-based calf milk replacer manufacturer Denkavit detailed the benefits of adding an electrolyte, which include:

Balances the loss of sodium, potassium, and chloride when depleted during a time of diarrhea. A good quality electrolyte will contain all three of these minerals.
Helps improve water absorption in the intestinal cells, specifically sodium help regulate this process. When sodium levels are low, the osmotic pressure in the intestinal lining of the calf cannot be properly regulated.
Corrects for a low blood pH. When sodium and potassium levels are decreased, the blood pH can drop, putting the calf at risk for acidosis. Moisture loss due to heat stress also can cause calves to become acidotic. In this case, a good quality electrolyte will contain a good alkalinizing agent (sodium bicarbonate).
Provides a source of energy to the calf. During a state of diarrhea or scours, some of the nutrients from the milk replacers are malabsorbed. A good quality electrolyte will contain a sugar base to provide energy, such as glucose or dextrose. Sucrose is not easily digested by the young calf and is not considered an effective sugar base in electrolytes.
- It is crucial to continue feeding milk when calves are suffering from diarrhea because oral rehydration therapy will never supply enough energy to correct the deficit.
Osmolarity is equal to or lower than that of the calf. A calf has bodily fluids at an osmolarity of 300-330 mOsm/L. If an electrolyte with an osmolarity >600 mOsm/L is fed, this can actually reverse the flow of water from the cells leading to further dehydration.

Renowned calf and heifer expert Dr. Jim Quigley with Cargill advised feeding 2 L of electrolytes midday or in the evening to preweaned calves when daily high temperatures are 85°F or higher.

Quigley’s one caveat: electrolytes NEVER should be added to whole milk or milk replacer.

Keep Cow Handling to a Minimum During Hot Weather

Tue, 28 Jun 2022 12:55:55 GMT

During the summer months, you’ll often see high school football players and athletes working out during the early morning hours while temperatures are still cool. Who can blame them?

As the thermometer starts to creep its way into the upper 80s, 90s or even the 100°F mark, nobody wants to put in physical work during the hottest part of the day - cows included.

As summer temperatures rise, dairy cows are at greater risk for heat stress. Heat stressed dairy cows suffer from:

reduced dry matter intake
reduced milk production
decreased fertility
lameness issues
metabolic issues

According to the University of Wisconsin-Madison Dairy Extension Team, it is important to minimize animal handling during bouts of heat to help prevent heat stress and improve animal welfare.

Know When It’s Too Hot

Animals can experience heat stress discomfort even during milder weather, especially as you factor in humidity. Knowing the daily Temperature Humidity Index (THI) can help producers plan activities around times when they anticipate heat stress in cattle.

The chart (below) is color-coded according to categories of heat stress ranging from mild (lightly shaded) to severe (darkly shaded) for lactating dairy cows.

(Farm Journal)

University of Wisconsin-Madison

Minimize Handling

While cows spend the majority of their day either resting or eating, they do spend chunks of time in the parlor, holding area or in headlocks.

According to the extension team, to prevent added heat stress, handle animals during the early morning hours before the temperature rises into the risky THI level. Limit the length of time animals spend in headlocks or other handling equipment where their stress from confinement may exaggerate the heat stress conditions.

When THI is 72 or higher, consider postponing animal handling related tasks which can be performed during cooler weather.

An animal’s internal temperature peaks approximately two hours after the environmental temperature peaks and it takes the animal four to six hours to lower their temperature back to normal. If possible, the evening hours should be left for the animals to cool down and not used for handling unless it is necessary.

Extra care should be taken if the evening temperatures do not drop below 70°F as cattle have no chance to recover before another day of heat and humidity. The longer the heat stretch lasts, the more stressful it is on cattle.

Keep Animals Calm

Animals who are nervous or stressed have higher core body temperatures. When handling or moving cows, move them slowly, calmly and quietly. If possible, try to move them in short distances. Plan ahead to avoid unnecessary movements.

Limit Transport

Trailer rides can be a stressful experience for cattle. Factor in hot temperatures and it can be animal welfare nightmare. The Dairy Extension Team recommends avoiding cattle transport in moderate to severe THI conditions. If possible, postpone transport until cooler and less humid weather arrives.

Provide Plenty of Water

No matter the time of year, clean drinking water should always be readily available for cattle. During the summer months, this becomes even more critical.

Check and clean waterers regularly and monitor increased consumption. As temperatures rise, many cattle may try to drink at the same time. Ensure the refill rate is adequate, so it allows all animals to drink. If necessary, consider adding additional temporary tanks.