Archive for Heat Stress

Modern Dairy Cows Suffer More Heat Stress: How Genetics, Barn Design, and Nutrition Can Help

Discover how genetics, barn design, and nutrition can help modern dairy cows combat heat stress. Are your cows suffering in the summer heat? Learn effective solutions now.

Every summer, as temperatures rise, dairy farmers face a hidden crisis: heat stress in dairy cows. This silent issue leads to decreased milk production and suppressed fertility rates, resulting in significant economic losses and impacting the global dairy supply. What makes modern dairy cows less resilient to heat stress than before? 

The answer lies in selective breeding for higher milk yield, which has inadvertently reduced heat tolerance. Heat stress is not just about animal health and comfort; it has substantial financial repercussions, costing farmers millions annually. 

We aim to explore solutions to mitigate these effects through genetics, improved barn design, and nutritional strategies. 

Join us as we uncover innovative solutions that promise relief to cows and farmers.

Adapting to Modern Challenges: Genetic Selection and Heat Stress in Dairy Cows

As dairy farming has evolved, genetic selection for high milk production has made cows more vulnerable to heat stress. Heat tolerance, the ability of an organism to withstand high temperatures, is a critical factor in this. The increased metabolism needed for higher yields generates more internal heat, compromising their heat tolerance. This physiological challenge necessitates interventions to ensure cow wellbeing and productivity. 

Countries like Australia and Italy have recognized the importance of heat tolerance by implementing genetic evaluations. These assessments involve analyzing the genetic makeup of animals to identify those better suited to handle heat. For instance, Italian data shows that daughters of bulls rated 105 for heat tolerance produce about 1.5 kg more milk under heat stress than those sired by bulls rated 95, translating to an economic difference of $1 per day per cow. The impact is significant, with 180 days of high temperatures annually in Italy. 

Integrating genetic evaluations into breeding programs can significantly reduce the effects of heat stress. Selecting heat-tolerant animals improves animal welfare and boosts productivity. As climate variability increases, the focus on genetic selection for heat tolerance will continue to grow, ensuring sustainable and profitable dairy farming worldwide.

Impact of Heat Stress on Feed Intake and Milk Production in Dairy Cows 

Heat stress significantly impacts the feed intake and milk production of dairy cows. Under heat stress, cows reduce their feed intake by 8-12%, leading to a drop in milk output. When a cow’s core body temperature rises above 38.8⁰C, it stands longer to dissipate heat, reducing blood flow to the udder and decreasing milk production. Cooling the cow’s core body temperature with fans providing wind speeds of at least 7 km/h and evaporative cooling systems can help. These methods imitate sweating, cooling the cow, improving comfort, and boosting milk production.

Maximizing Airflow for Heat Stress Mitigation: Modern Barn Designs and Fan Technology 

Effective air movement is crucial for cooling dairy cows. Modern barns feature retractable side walls to enhance natural airflow and reduce heat stress. 

Natural ventilation might not suffice on still, humid days. Thus, fans are essential. Eric Bussem from Abbi-Aerotech BV recommends positioning fans to blow fresh outside air into the barn, which improves airflow and energy efficiency

Cross-ventilation ensures all cows get fresh air, preventing competition for more excellent spots. Advanced fan technology, like direct-drive models, further boosts energy efficiency and cuts maintenance costs. New fans from Abbi-Aerotech, for example, use only 15 W/h under standard conditions, much less than a typical light bulb. 

By using modern barn designs and advanced fan systems, dairy farmers can better manage heat stress, improving animal welfare and productivity.

Enhancing Cow Comfort and Productivity through Cross Ventilation in Barns

Cross ventilation in barns, achieved by placing fans to blow air across from the sides, offers significant benefits over traditional end-to-end systems. This setup shortens the air travel distance, providing constant fresh air throughout the barn. Directing airflow from the sides gives each stall the same cooling effect, reducing cow competition for the best-ventilated spots. This cross-ventilation system is critical in enhancing cow comfort, promoting better rest, and increasing milk production. 

Even cooling across the barn enhances cow comfort, promoting better rest and increased milk production. Equalized air distribution encourages cows to lie in their stalls, which is crucial for optimal milk synthesis. This system reduces stress and distributes the herd more evenly, improving overall welfare and productivity.

Overlooked Heat Stress: The Critical Impact on Dry Cows 

While lactating cows often get the most attention, the heat load on dry cows is a crucial yet frequently overlooked issue in managing heat stress in dairy herds. Dr. Geoffrey Dahl from the University of Florida has highlighted significant consequences of heat stress during the dry period, affecting subsequent lactation, overall health, and calf development. His research shows that cows experiencing heat stress during these six weeks produce about 2 liters less milk per day in their next lactation than cooled ones. Heat-stressed dry cows also have fewer alveoli in the udder, reducing milk production, and are more susceptible to retained placenta, mastitis, and respiratory diseases. 

The adverse effects extend to the offspring as well. Calves from heat-stressed mothers are born earlier, with lower birth weights and poorer survival rates. These issues persist through weaning and puberty, affecting growth rates and immune status. Reduced milk yields are also seen in these calves’ daughters, continuing the cycle of heat stress impacts into future generations. 

Comprehensive Heat Stress Management: A Responsibility for Dairy Farmers

Maintaining hydration is critical to managing heat stress in dairy cows. Easy access to clean water is essential, but effective hydration management goes beyond that. Comprehensive strategies are needed to cool cows from the inside out, supporting feed and water intake, replenishing nutrients, and promoting gut health during heat stress. 

Bovine BlueLite from TechMix is a leading product designed to maintain optimal hydration in dairy cattle. Available in soluble powder and pellet forms, it combines electrolytes with energy sources to preserve cell volume and fluid balance. Fortified with vitamins and antioxidants, BlueLite helps combat oxidative stress, reducing heat’s adverse effects on production and reproduction. 

Research shows that supplementing cows with Bovine BlueLite during heat stress helps decrease body temperatures and sustain milk production. Integrating BlueLite into a farm’s heat stress management can improve herd well-being and productivity during challenging summer months.

The Slick Gene: A Beacon of Hope for Heat Tolerance in Dairy Cows

Introducing the “slick” gene—known for its short hair coat and extra sweat glands—is a game-changer for boosting heat tolerance in dairy cows. This gene, from Bos Indicus or Zebu cattle, was integrated into Holsteins via the Senepol breed to enhance their productivity and adaptability in hot climates. 

Pioneering this effort, Raphy Lopez of Puerto Rico combined top US Holstein lines with Senepol cattle to develop high-producing, heat-tolerant cows. The University of Florida furthered this work by importing slick genetics, making notable bulls like Slick Gator and Slick Blanco available. 

A breakthrough came with the breeding of El-Remanso Sinba-Red. This homozygous slick bull ensures that all offspring carry the slick gene. Mark Yeazel’s homozygous slick red and polled bull, Ja-Bob Eclipse, has recently sparked renewed interest in slick breeding. 

Beyond the Americas, Rudolf Haudenschild and the KeepCool Syndicate in Switzerland actively promote slick genetics in Europe. These global efforts highlight the slick gene’s potential to help dairy cows stay productive and healthy despite rising temperatures worldwide.

The Bottom Line

Modern dairy cows face increasing vulnerability to heat stress due to selective breeding for higher milk production, which has inadvertently decreased their heat tolerance. Utilizing a holistic approach that includes genetic selection for heat tolerance, improved barn designs with better ventilation, and nutritional strategies to maintain hydration and reduce internal heat production can significantly mitigate these adverse effects. 

Global implementation of genetic evaluations and the slick gene integration show promise. Evidence from Italy and Australia demonstrates real-world benefits like increased milk production and better overall bovine health. Additionally, innovative barn designs, advanced fan technologies, and thorough hydration strategies offer practical solutions to this pervasive issue. 

It’s important to acknowledge the broader implications. Heat stress affects not only immediate productivity and health but also the long-term well-being of future generations, impacting calves and subsequent lactations. The economic losses are substantial, amounting to millions annually, highlighting the need for proactive measures. 

Addressing heat stress in dairy cows requires a comprehensive approach. By leveraging advancements in genetics, technology, and nutrition, the dairy industry can develop more resilient herds capable of thriving despite rising temperatures, thus ensuring sustained productivity and animal well-being.

Key Takeaways:

  • Genetic Selection: Modern dairy cows are less heat tolerant due to selective breeding for higher milk production.
  • Heat Mitigation Strategies: Housing with better temperature control, nutritional strategies to reduce internal heat, and incorporating the “slick” gene are crucial measures.
  • Air Movement: Effective ventilation through fans and open barn designs enhances cooling and cow comfort.
  • Dry Cow Consideration: Heat stress during the dry period significantly impacts future lactation yields and overall cow health.
  • Hydration: Rehydration is essential for maintaining feed intake and overall health during heat stress.


Heat stress in dairy cows is a significant issue that leads to decreased milk production and suppressed fertility rates, causing economic losses and impacting the global dairy supply. Selective breeding for higher milk yield has reduced heat tolerance, necessitating interventions to ensure cow wellbeing and productivity. Countries like Australia and Italy have implemented genetic evaluations to reduce heat stress effects, improving animal welfare and productivity. Modern barn designs with retractable side walls and advanced fan systems can help dairy farmers manage heat stress, improving animal welfare and productivity. Cross-ventilation in barns shortens air travel distance, provides constant fresh air, and directs airflow from the sides, reducing competition for the best-ventilated spots. Heat stress affects lactation, overall health, and calf development, resulting in lower milk production and poorer offspring. Dairy farmers must manage heat stress comprehensively, including maintaining hydration, supporting feed and water intake, replenishing nutrients, and promoting gut health during heat stress.

Learn more:

How to Keep Your Dairy Cows Cool and Feed Fresh for Higher ROI

Prevent feed spoilage in cows and boost dairy profits. Learn how to combat heat stress and contamination in your herd. Ready to improve your ROI this summer?

Cows, hailing from Ice Age ancestors, thrive best in the cool 40-60°F (4.4-15.6°C) range. In the summer heat, they struggle, mainly when fed unstable, spoiled feed. This situation isn’t just uncomfortable—it’s detrimental to their health and your dairy farm‘s profitability. 

Heat stress and spoiled feed can drastically reduce a cow’s intake and production, making summer a tough season for dairy farmers

Recognizing cows’ natural preference for cooler climates underpins the need to effectively tackle heat stress and feed spoilage. It’s not only about comfort but also about protecting your herd and maximizing your investment returns. The solution begins with proper feed management.

Unseen Threats: The Real Culprits Behind Feed Spoilage 

Many people think mold is the main issue with feed spoilage. Still, the real problem is the rapid growth of spoilage microorganisms, especially wild yeasts, in warm and humid conditions. These tiny organisms are nearly invisible but can cause significant nutrient losses before mold even appears. They thrive when temperatures consistently exceed 60°F/15.6°C, exceptionally when moist. 

Wild yeasts lie dormant on crops and come alive when exposed to air, such as during silo opening. Under the right conditions, their population can double in about two hours, leading to massive feed contamination. This rapid growth destroys the highly digestible nutrients crucial for cattle health and productivity

As yeasts consume sugars and lactic acid in silage, they produce heat and increase the pH, allowing mold and bacteria to grow. This accelerates spoilage and causes significant dry matter (DM) losses, reducing feed quality. Aerobic spoilage driven by these microorganisms can lead to DM losses as high as 30% to 50%, drastically impacting the feed’s nutritional value and profitability.

High Yeast Counts: A Silent Saboteur in Your Silage 

Hours ExposedYeast Count (per gram)

High yeast counts can drastically impact aerobic stability, leading to significant nutrient losses. When yeasts proliferate, they consume highly digestible nutrients for your dairy herd‘s health and productivity. Aerobic spoilage can cause dry matter (DM) losses between 30%-50%. Even short-term air exposure can result in up to a 6% DM loss in corn silage within a couple of days (Ranjit and Kung, 2000). 

As yeasts increase, they raise the temperature and pH of silage, making it prone to bacterial and mold contamination. This chain reaction reduces feed quality and digestibility, hurting intake and production. For example, high-moisture corn in an aerobic environment saw a rise in yeast levels and a decline in milk yield over 14 days (Kung 2010). 

Financially, a 15°F/8.4°C rise in a ton of 30% DM silage can consume over 6.3 MCal of energy, equating to about 20 pounds (or 9 kilograms) of lost milk production per ton of silage. This increases feed costs as you need to replace lost nutrients and DM, affecting profitability. 

Understanding and controlling yeast levels are crucial for maximizing cattle health and improving the return on investment in your dairy operations.

When Prevention Fails: Practical Strategies to Counter Feed Spoilage

When prevention is no longer an option, there are still ways to mitigate feed spoilage’s impact. One strategy is dilution: mix small amounts of spoiled silage with fresh feed, but keep it minimal—a mere 5% spoilage can reduce feed digestibility

Chemical additives are another tool. They inhibit spoilage microorganisms and enhance silage stability. For best results, choose products backed by research. 

Minimizing oxygen exposure is crucial. Smaller, frequent feedings reduce air exposure time, limiting spoilage. Ensure your silage is tightly packed and well-covered to keep oxygen out and maintain feed quality.

Setting the Stage for Success: Steps to Prevent Contamination 

Producers can take several steps to prevent contamination and set themselves up for success. The most important thing is good silage management. 

  • Harvesting 
    Start with proper harvesting. Ensure forage is at the right maturity and moisture level. Chop and process it correctly, fill quickly, and pack it tightly (minimum 45 pounds fresh weight per cubic foot or 720 kilograms per cubic meter). Avoid delays, and cover, weigh, and seal the silage immediately to prevent air exposure. 
  • Inoculation 
    Consider using a high-quality forage inoculant. Research shows these products improve aerobic stability both in the silo and during feeding. Look for an inoculant with specific strains, applied at 400,000 CFU/g for forage or 600,000 CFU/g for high-moisture corn. This can prevent wild yeast growth and enhance stability. Such inoculants ensure fast fermentation, better digestibility, and extended aerobic stability, maintaining silage hygiene. A proven inoculant maximizes forage quality and strength, leading to healthier cattle and a better ROI.
  • Monitoring 
    Regular monitoring is crucial for maintaining feed quality and your cows’ health. By catching early signs of spoilage, you can prevent more significant issues and keep productivity high.  Use silage temperature probes to detect potential spoilage. These probes help you spot temperature changes that signal aerobic instability. Regular checks at different depths are essential to early detection.  Send samples to a lab for a more detailed analysis. This can reveal harmful microbes and spoilage agents not visible to the eye. Combining these methods ensures your cows get the best nutrition.

The Bottom Line

Unseen threats like wild yeasts can silently sabotage your silage, leading to nutrient and dry matter losses. High yeast counts harm feed intake, milk production, and profitability. Practical steps like proper harvesting, effective inoculants, and vigilant monitoring can help mitigate these issues and protect your cattle’s health. 

Feed quality doesn’t just maintain health—it impacts your return on investment. The calm, stable feed can enhance cow performance and improve your financial outcomes. Remember, hot cows hate hot feed, and preventing spoilage results in healthier herds and better profits.

Key Takeaways:

  • Cows prefer cooler temperatures ranging from 40-60°F (4.4 – 15.6°C) due to their lineage tracing back to the Ice Age.
  • Heat stress in cows is exacerbated by unstable, heated, and spoiled feed, which fosters harmful microbes and compromises intake, performance, and profitability.
  • Unseen spoilage microorganisms, particularly wild yeasts, proliferate rapidly in warm, humid conditions, causing nutrient losses before mold is even visible.
  • Aerobic spoilage can lead to dry matter (DM) losses of up to 30%-50%, further diminishing feed quality and impacting ROI.
  • Effective feed management strategies include dilution, chemical additives, and proper harvesting techniques to minimize oxygen exposure and microbial growth.
  • Implementing high-quality forage inoculants and regular monitoring of feed temperatures and stability are crucial preventive measures.
  • Properly managed feed results in healthier cows, improved milk production, and better overall profitability for dairy farms.

Summary: Cows, native to the Ice Age, thrive in cooler climates, but summer heat can lead to instability and spoiled feed, negatively impacting their health and profitability. This makes summer a challenging season for dairy farmers, as they must recognize cows’ natural preference for cooler climates for effective feed management. The main issue with feed spoilage is the rapid growth of spoilage microorganisms, especially wild yeasts, in warm and humid conditions. These microorganisms cause significant nutrient losses before mold appears, leading to massive feed contamination. Aerobic spoilage driven by these microorganisms can lead to DM losses as high as 30% to 50%, significantly impacting the feed’s nutritional value and profitability. Practical strategies to counter feed spoilage include dilution, chemical additives, and minimizing oxygen exposure. Proper harvesting, inoculation, and monitoring are essential steps to prevent contamination and maintain productivity.

When Does Heat Stress Impact Calves?

Discover when heat stress affects dairy calves and learn actionable strategies to protect their health and growth. Are your calves at risk? Find out now.

Contrary to a common but flawed assumption that calves can tolerate heat stress better than mature cows due to their unique physiological traits, Dr. Jimena Laporta’s extensive research has shed new light. Her findings reveal that the thermoneutral zone for calves closely mirrors that of adult cattle, ranging from 50-72°F. When ambient temperatures deviate from this optimal range, calves must expend additional energy to regulate their internal body temperature, compromising their growth and immune function. This article, grounded in Dr. Laporta’s research, will explore the factors influencing heat stress in dairy calves, such as their thermoneutral zones, age and size considerations, and the Temperature-Humidity Index (THI). We will also examine the regional variations in heat stress benchmarks between Florida and Wisconsin and propose practical strategies to alleviate heat stress and foster optimal calf growth.

Understanding Heat Stress: When Calves Are Most Vulnerable

Heat stress in dairy calves poses a significant threat not only to their immediate health but also to their long-term productivity. Contemporary research dispels the conventional belief that calves are inherently more resilient to heat stress than adult cows. 

Calves subjected to elevated temperatures face the challenge of redirecting energy from critical growth and immune functions towards thermoregulation, thereby stunting growth rates and heightening vulnerability to diseases. These early-life setbacks impair their development and adversely affect their future productivity as mature dairy cows

Multiple factors, including age, physiological status, and environmental conditions, play pivotal roles in influencing calf heat stress. Age significantly impacts thermoregulation, with younger calves lacking fully developed mechanisms. Physiological status, encompassing health and nutrition, affects heat dissipation and immune efficiency. Environmental conditions such as temperature, humidity, and wind speed exacerbate the stress, with high moisture particularly hampering cooling efforts. 

Prenatal exposure to heat stress predisposes calves to greater thermal sensitivity post-birth, underscoring the critical need for strategic management practices for dairy calves

Addressing heat stress in calves is imperative for holistic herd management, safeguarding future productivity, and ensuring sustainability. Effective strategies, elaborated in the practical tips section, include providing adequate shade, offering access to cool water, and implementing mechanical ventilation systems.

The Science Behind Calf Heat Stress: Key Thermoneutral Zones

It is a prevailing misconception that calves possess a heightened resistance to heat stress due to certain physiological traits. While they exhibit a greater surface area relative to their body mass, facilitating heat dissipation, this perceived advantage is counterbalanced by other factors. The underdevelopment of their rumens results in less metabolic heat generation, ostensibly offering an edge in heat management. However, empirical research reveals a more complex reality.  

Calves function optimally within a thermoneutral zone of 50-72°F. Deviations from this temperature range, whether towards the higher or lower spectrum, necessitate energy allocation towards thermoregulation, undermining growth and immune system efficacy.  

Grasping the repercussions of temperature fluctuations beyond this thermoneutral zone is imperative. Elevated temperatures trigger thermoregulatory responses, notably increased respiration and distinct behavioral adjustments. This redirection of energy comes at the expense of growth-critical reserves.  

The long-term implications of sustained heat stress are significant. Studies underscore discernible behavioral shifts in heat-affected calves, including alterations in standing and lying postures. These insights are instrumental in crafting effective heat mitigation strategies.  

Comprehending the specific thermoneutral requisites of calves is critical. Such awareness is pivotal in alleviating heat stress, thus nurturing healthier and more robust dairy calves. Environmental management and tailored heat reduction initiatives transcend mere operational tweaks; they are strategic investments in the enduring productivity and welfare of the herd.

Factors Influencing Calf Heat Tolerance: Age, Size, and Environment

In examining the intricate matter of calf heat tolerance, it becomes imperative to analyze the interconnected dynamics of several critical factors. Age and size hold significant sway. Younger and smaller calves frequently exhibit increased susceptibility to heat stress due to their immature thermoregulatory systems. Conversely, while older and larger calves may demonstrate enhanced resilience, they are not exempt from the challenges posed by extreme heat. 

Environmental parameters such as wind speed, ambient temperature, and relative humidity are pivotal in determining heat tolerance. Elevated wind speeds can facilitate heat dissipation, providing a cooling effect that mitigates high-temperature stress. However, ambient temperature is the primary driver of heat stress, with rising temperatures directly correlating with increased physiological strain on calves. Furthermore, high relative humidity exacerbates this issue by hindering the evaporation of sweat and respiratory moisture, thus compromising the calves’ natural cooling mechanisms. 

Integrating these factors allows for a more holistic approach to mitigating the adverse effects of heat stress on dairy calves. Recognizing the specific needs and limitations of calves across various growth stages and environmental conditions equips dairy farmers with the ability to implement more effective heat abatement strategies. This proactive approach ensures the sustained health and optimal performance of their livestock.

Temperature-Humidity Index (THI) and Its Impact on Calves

The Temperature-Humidity Index (THI) is a pivotal metric within the dairy farming sector, offering a nuanced understanding of how ambient temperature and relative humidity collectively impact livestock. Compared to ambient temperature alone, THI provides a more precise indicator of heat stress. Its relevance in dairy farming cannot be overstated, as it directly correlates with an animal’s capacity to maintain thermal homeostasis and achieve optimal physiological performance. For mature dairy cows, a THI of 68 is broadly recognized as the threshold at which heat stress begins, heralding the onset of thermoregulatory difficulties and subsequent declines in productivity. 

Nevertheless, Dr. Jimena Laporta’s extensive research elucidates that calves exhibit distinct THI thresholds. Her findings indicate that calves in Florida start showing significant respiratory changes at a THI of 65, with rectal temperature alterations appearing at a THI of 67. Conversely, calves in Wisconsin exhibit both respiratory and rectal temperature changes at a higher THI of 69. This research underscores that calves are markedly susceptible to environmental heat stress despite their supposed physiological advantages in heat dissipation. Consequently, there is a critical need to adopt tailored management practices that consider regional climatic disparities.

Regional Differences: Florida vs. Wisconsin Calf Heat Stress Benchmarks 

detailed examination of THI thresholds in Florida and Wisconsin reveals noteworthy differences in calf heat stress reactions. In Florida, calves exhibited sudden changes in respiratory rates at a THI of 65 and rectal temperatures at 67. Conversely, these indicators were noticeable in Wisconsin at a THI of 69. This data highlights the significant influence of regional climates on calf thermal tolerance.  

The broader ramifications for dairy farming are profound. Heat stress can substantially hinder calf development and their long-term performance. Heat-stressed calves often consume less milk replacer and starter grain, stunting their growth. Moreover, the research associates early-life heat stress with delayed conception and reduced milk yield in the first lactation, culminating in notable economic setbacks. As Laporta argues, addressing heat stress in calves is a strategic investment in the future productivity of the herd.  

Laporta and her team are investigating advanced methods for combating heat stress, including mechanized ventilation systems powered by solar panels for individual calf hutches. These innovations alleviate heat stress and adhere to sustainable agricultural practices. This dual advantage illustrates how contemporary technology can address traditional farming challenges.  

Dairy producers should provide sufficient shade to enhance calf well-being, ensure access to cool water, and employ cooling mechanisms such as fans and misters. Monitoring THI and adjusting practices accordingly can mitigate heat stress. It is imperative to consider regional differences to tailor strategies for specific environmental conditions.  

Investing in heat stress abatement for calves is essential for their immediate welfare and long-term herd management strategy. As Laporta emphasizes, “We are investing in our calves for life. Heat reduction should be one of those investments.” Prioritizing the thermal comfort of young dairy animals fosters robust growth, improved reproductive performance, and sustainable productivity, safeguarding operations against heat stress challenges.

Practical Tips for Managing Calf Heat Stress on Your Farm 

Strategic mitigation of heat stress is paramount in safeguarding calves’ health and developmental trajectory. Dr. Laporta’s robust research underscores the imperative for early intervention, highlighting benefits that extend beyond immediate welfare to long-term productivity and robustness. By adopting effective, early heat abatement strategies, farmers can ensure their calves have the optimal start, translating to healthier, more productive cows in the future.  

Innovative solutions, such as mechanically ventilating individual calf hutches using solar-powered fans, are currently being explored. This technique promises to sustain a cooler micro-environment, alleviating calves’ physiological stress. Integrating renewable energy offers a sustainable management method and an eco-friendly approach to enhancing animal welfare.  

Adopting such advanced methods can yield significant, long-term benefits. Calves experiencing less heat stress are more likely to consume adequate amounts of milk replacer and starter grain, enhancing growth metrics. Additionally, mitigating heat stress during early life stages correlates with improved immune function, potentially reducing future veterinary expenses and health challenges. Thus, farmers can expect more resilient herds, ultimately contributing to the sustainability and profitability of the dairy operation.  

Moreover, shade provision remains a fundamental, low-cost option that should be considered. Shade helps reduce the temperature within calf hutches, directly lowering the calf’s body temperature and respiration rate. Simple measures, such as positioning calf hutches under trees or installing shade cloth, can yield substantial benefits with minimal investment. This evidence-based approach promotes calf welfare and ensures optimal growth and development.  

Long-term productivity benefits also include early-life interventions that enhance reproductive success. Calves that experience less heat stress demonstrate better feed efficiency and growth rates, leading to earlier and greater fertility. This ultimately translates to higher milk production in their first lactation, underscoring the economic viability of investing in heat stress abatement strategies.  

By committing to effective heat abatement measures, dairy farmers are, in essence, securing their herds’ future efficiency and health, thereby promoting a stable and productive dairy operation. Recognizing the profound impact of heat stress on calves and acting upon this with scientifically validated methods paves the way for a more sustainable and prosperous dairy industry.

The Bottom Line

In the evolving landscape of dairy farming, the imperative to prioritize calf rearing shockingly threads through the tapestry of heat stress management—a commitment once predominantly focused on mature cattle. The distinct THI thresholds observed across diverse regions unravel the intricate environmental variables affecting calf health. Cutting-edge research on heat abatement strategies unveils the potential for immediate health improvements while bolstering long-term productivity. Embracing pioneering solutions like solar-powered ventilation for calf hutches reflects a visionary stance dedicated to fostering dairy herds’ enduring well-being and performance from their earliest stages. Dr. Jimena Laporta said, “We are investing in our calves for life.” The battle against heat stress should be integral to that lifelong investment.

Key Takeaway:

Calf rearing, often overshadowed by the focus on mature cattle, is crucial for managing heat stress effectively. Embracing innovative solutions like solar-powered ventilation for calf hutches can significantly enhance calf health and productivity. Dr. Jimena Laporta emphasizes that investing in calf heat stress abatement is investing in the longevity and sustainability of the entire dairy herd.

Summary: Dr. Jimena Laporta’s research shows that calves can tolerate heat stress better than adults due to their thermoneutral zone resembling adult cattle. However, when temperatures deviate from this optimal range, calves must expend more energy to regulate their internal body temperature, compromising their growth and immune function. This poses a significant threat to their health and long-term productivity. Age, physiological status, and environmental conditions influence calf heat stress, with age significantly impacting thermoregulation and physiological status affecting heat dissipation and immune efficiency. Environmental conditions, such as temperature, humidity, and wind speed, exacerbate the stress. Prenatal exposure to heat stress increases calves’ thermal sensitivity post-birth, highlighting the need for strategic management practices for dairy calves. Addressing heat stress is crucial for holistic herd management, future productivity, and sustainability.

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Global Warming and Its Effect on Dairy Cattle

Over the past few weeks we have certainly seen some extreme weather conditions around the world.  Those on the east coast of North America have been hit by record cold temperatures.  At the same time, those in Australia have been experiencing record hot temperatures.  These extreme weather conditions have many wondering what effects “Global Warming” will have on the dairy cattle  There has been lots of coverage in the media about  dairy cattle and their alleged contribution to greenhouse gases and how that is contributing to Global Warming.  Very little has been addressed about the effects extreme weather conditions have on the dairy cattle themselves.  One thing appears certain.  Extreme heat waves and cold fronts are the new ‘normal’.

As producers know, cow and calf comfort is one of the most important factors in milk production and growth.  As more and more producers are experiencing extreme temperatures, keeping their animals comfortable is becoming harder.  Drastic increases or decreases in ambient temperature affects animal production systems by affecting the health, reproduction, nutrition etc. of the animals and thereby results in poor performance, inferior product quality, outbreak of novel diseases, etc.  Dairy cattle are   more susceptible to increased ambient temperature than other ruminants, because of their high metabolic rate and the poor water retention mechanism of their kidney and gastrointestinal tracts.  Young stock are not immune to these weather stresses either.

Greater temperature shifts and shifts that are more frequent seem to be the most obvious weather changes that will have effects on dairy cattle.  It is forecasted that we can expect even greater atmospheric temperature changes.  Therefore these issues are going to come to the forefront.  The following are the five major impacts   that global warming will have on dairy cattle.

  1. Ambient temperature’s effect on Dry Matter Intake (DMI)
    When cows are stressed their Dry Matter Intake (DMI) decreases.  As the heat rises DMI decreases.  Feed consumption by dairy cattle starts to decline when average daily temperature reaches 25 to 27 Centigrade  (77 to 81 Fahrenheit) and voluntary feed intake can be decreased by 10-35% when ambient temperature reaches 35 C (95 Fahrenheit) and above.  Conversely, cows that are experiencing extreme cold weather conditions increase their DMI intake drastically, but instead of the consumption being converted in to milk production, a much larger portion of their energy is committed to their maintenance energy requirements.  Thermal cold stress conditions result in 20-30% more maintenance energy requirement and an ensuing reduction in the amount of net energy available for growth and production.
  2. Increased respiratory rate
    When dairy cows experience increased thermal stress, their heart rate rises.  The heart rate of the animal under thermal heat stress is higher to ensure more blood flow towards peripheral tissue to dissipate heat from the body core to the skin.  This increased effort takes much needed energy away from milk production.  Respiration rate of the animal can be used as an indicator of the severity of thermal load but several other factors such as animal condition, prior exposures to high temperature etcetera should be considered to interpret the observed respiration rate.
  3. Decreased conception rates
    As weather stress increases, dairy reproduction function decreases, resulting in decreased conception rates.  This is a result of thermal stress that causes imbalance in secretion of reproductive hormones.  High ambient temperature has also been reported to increase incidence of ovarian cysts.  Plasma progesterone levels in animals under high ambient temperatures are low compared to animals that are experiencing thermal comfort.  It has also been reported that high ambient temperature causes poor quality of ovarian follicles resulting in poor reproductive performance in cattle.  Fertility of cattle is also reduced due to low intensity and duration of estrus caused by reduced luteinizing hormone (LH) and estradiol secretion during thermal stress.  In addition, thermal stress also causes decreased reproductive efficiency by increasing the calving interval. Calves born from dams under thermal stress were found to be of lower body weight than those from normal cows.  Additionally the dams had reduced lactation performance due to the carryover effects of thermal stress which occurred during the prepartum period.
  4. Decreased Metabolic Responses
    Under heat stress metabolism is reduced, which is associated with reduced thyroid hormone secretion and gut motility, resulting in increased gut fill.  Plasma growth hormone concentration and secretion rates decline with high temperature (35 ºC / 95 ºF).  Ruminal pH is typically lower in heat stressed cattle
  5. Decreased Milk Production
    Reduction in milk production is one of the major economic impacts of climatic stress upon dairy cattle.  Decrease in milk yield due to thermal heat stress is more prominent in Holstein than in Jersey cattle (Read more…).  Decreased synthesis of hepatic glucose and lower non esterified fatty acid (NEFA) levels in blood during thermal stress causes reduced glucose supply to the mammary glands and results in low lactose synthesis, which in turn leads to low milk yield.  As mentioned earlier, reduction in milk yield is further intensified by decrease in feed consumption by the animals to compensate for high environmental temperature.  Actually 35% of reduced milk production is due to decreased feed intake while the remaining 65% is attributable directly to the thermal stress.  Other factors resulting in reduced milk production during thermal stress are decreased nutrient absorption, negative effects on rumen function and hormonal status and increased maintenance requirements.  These all mean that there is reduced net energy available for production.

To combat heat stress check out these articles (Read more: Are you feeling the heat?  and Heat Stress on Dairy Cattle) and to combat cold stress (Read more: COMMON SENSE, COWS and the UN-COMMON COLD of 2014!“COLD CALVES” – The Next Drama Coming to a Calf Pen Near You! and Cold Weather Effects on Dairy Cattle)

The Bullvine Bottom Line

There is no question that the world’s temperatures are changing because of atmospheric pressure changes caused by Global Warming.  Warming or cooling of the climate system of the earth has multifaceted effects on animals.  Intensification and increased frequency of thermal stress due to global warming has the most prominent impact on dairy cattle and causes   different physiological, metabolic and production disturbances.  The importance of responding to thermal stress has been increased for dairy farmers in tropical, subtropical and even in temperate regions of the world due to atmospheric warming.  As these effects increase, it will be increasingly urgent for the milk producers of the world to provide environments that are able to combat these effects and offer the greatest comfort for their cattle.  Global Warming is actually Global Warning for the dairy industry.


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