As we roll through the summer months, signs of heat stress in beef cattle become an increasing concern for those in the industry. An inability to dissipate heat causes heat stress in beef cattle and can lead to reductions in growth rate, health, milk production, reproductive efficiency and survival associated with heat stress. These contribute to significant losses to producers. While the cost of heat stress to the livestock industry is difficult to calculate accurately, several estimates have been made. St-Pierre et al. (2003) estimated up to $2.4 billion dollars in heat stress-related losses across all species within the US, with more than $350 million associated with the beef industry.

Typically, feedlot cattle are more susceptible to heat stress than cattle on pasture. In the feedlot, heat stress-related animal death costs ~$5,000 per head (Mader, 2002). Since those estimates were made, heat waves have become more frequent. A heat wave in 2006 resulted in the death of 25,000 cattle in California (Nienaber & Hahn, 2007), costing the dairy industry $1 billion (CDFA, 2006). In June 2009, more than 2,000 cattle died during a heat event in Nebraska. Farmers in Iowa reported upwards of 4,000 head of cattle lost in a 2011 heat wave. There have continued to be heat stress related incidents affecting cattle.

As research has delved into the effects of heat stress that reach far beyond production measures, it has become clearer that even when cattle do not show signs of heat stress, they may still be negatively impacted. Some hidden costs of heat stress include greater incidence of rumen acidosis, laminitis and dark cutting beef. Further, conception rates, sperm quality, milk yield, gut barrier integrity and immune function are adversely affected.

What factors can lead to beef heat stress?

While beef cattle are more resilient to heat stress than many other species, they still suffer negative effects. Even cattle exposed to the same environmental conditions and management practices vary widely in their ability to handle high environmental temperatures. Below are some key areas identified as indicators of an animal’s ability to cope with heat stress and suggestions on how to address them.

1. Genetics

• Bos indicus breeds have greater heat tolerance than continental breeds. Choosing location-appropriate breeds or crossbreds and timing breeding to best suit local conditions can mitigate many heat stress problems for calves.
• Cattle with dark hides are more susceptible to heat-related issues. In a group of closely related cattle with different hide colors, researchers found a 2°F higher core body temperature in cattle with dark hides. 
• Hair length is considered a moderately heritable trait. The slick gene found in Senepol cattle and Spanish-origin breeds results in a shorter coat and correlates to heat tolerance in cattle. 
• In addition to coat length, the timing of shedding is also a factor. Adjusted 205-day body weight was 24.1 pounds higher in calves from dams that shed by May in a trial by researchers at Mississippi State University and North Carolina State University.
• Calmer cattle have been shown to be more heat tolerant than excitable ones. This is likely due to reduced stress response to handling, leading to lower metabolic activity and heat production in the animal.

2. Health

• As cattle do not sweat effectively, they primarily use respiratory cooling to regulate body temperature. Thus, respiratory health is critical to managing a high heat load. Research at the Meat Animal Research Center (MARC) shows that cattle treated for pneumonia any time between birth and slaughter have a 10.5% higher respiration rate under stressful conditions in the feedlot.
• Cattle undergoing heat stress are more susceptible to illness, but the converse is also true. Cattle in poor health going into a heat event may not have adequate energy reserves to adjust metabolic activity to facilitate body cooling.

3. Production stage

• A feedlot is generally hotter than pasture due to radiant heat from dirt and concrete pads and the lack of shade and water typically available to pastured cattle.
• Heavier cattle are at more risk. The development of fat cover reduces the efficacy of heat dissipation mechanisms, with more heat from digestion and metabolism retained in the body. Cattle at the end of finishing should be watched closely for heat stress, as should cows with higher BCS.
• Adult animals can become heat-stressed at temperatures as low as 80°F if there is high humidity or little air movement. While calves are more heat-tolerant than mature animals, they are still susceptible to heat stress-related reductions in feed digestibility and energy redistribution, leading to lower growth and immunity.

4. Previous exposure to heat

• Cattle previously exposed to high temperatures are better able to tolerate additional heat events. Cattle producers in southern regions should be aware that cattle brought in from northern areas are likely to be much more sensitive to heat stress.
• Heat stress can negatively affect the immune function, growth, milk production and metabolic resiliency of cattle, even after the high temperatures have passed.

The local environment also plays a role in how well cattle handle the heat. Cattle do not dissipate heat as effectively as other species when temperatures are high. They accumulate a heat load during the day and dissipate heat at night as temperatures decline. When making management decisions in hot weather, remember that a cow’s core temperature peaks two hours after environmental temperature peaks, and it takes at least six hours for cattle to dissipate their heat load. Thus, if nighttime temperatures do not drop sufficiently, cattle will accumulate heat they cannot disperse. Therefore, a temperature-humidity index (THI) alone may not predict cattle heat stress because it does not account for this accumulated heat load.

How to manage heat stress in beef cattle

The best ways to manage heat stress in cattle involve planning practices that limit stress and provide cattle with cooling methods when needed. The USDA-ARS has excellent resources for forecasting and managing heat stress. Below are some suggestions to keep in mind:

• When possible, a shaded area should be provided to allow 20–40 square feet per animal, with the shade placed at least eight feet above the ground to allow good airflow. 
• Cattle increase respiration with temperature rises, necessitating higher water intakes. For growing animals, a temperature increase from 70–90°F nearly doubles water requirements. Ensure clean, cold water is available, with at least three linear inches of water space per head.
• Heat production from digestion peaks 4–6 hours post-feeding. Adjusting feeding times to provide 70% or more of feed in the evening allows cattle to digest during the coolest portion of the day.

• While windbreaks can be beneficial in the winter, if possible, they should be removed during the summer to allow for better air circulation. Similarly, limiting brush height in pastures can aid in keeping cattle cool.       
• Heavy fly loads will cause cattle to bunch together, exacerbating heat issues. A strong fly control problem is critical for management during hot weather.
• Watch the weather and, when possible, avoid working cattle on the hottest days and limit holding times where they are bunched or away from shade and/or water. If cattle need to be worked, do so in the early morning while they have low body temperatures and work slowly and calmly to help them manage the multiple stressors of heat and working.
• Sprinklers can be used to soak animals and aid evaporative cooling. Sprinklers should have a large droplet size, be used intermittently to limit mud formation and positioned away from bunks and feeders. Sprinklers should be considered preventative and require acclimation (once used, they must stay in use).

Some aspects of nutrition can also be considered to aid cattle in managing hot weather. Dietary protein should be examined as urea/urine production from excess protein is energetically costly and heat-generating. Similarly, high-forage diets can be problematic, as the heat produced from digesting fibrous material is much higher than that from grains and concentrates. However, cattle are more susceptible to acidosis during heat stress, so concentrate intake should be closely managed. Research indicates that lowering the energy content of the diet will decrease the heat load on the animals, with a general recommendation to reduce the diet energy content by 5–7%. Some feed additives have been proven to aid cattle during heat stress by helping maintain rumen pH balance, supporting digestion and through other actions. These additives can help maintain feed intake and health during heat stress.

Ultimately, managing beef cattle is a multi-faceted challenge that requires balancing the specifics of the cattle, environment and facilities of each individual production program.

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The pathology of cattle consuming endophyte-infected tall fescue varies greatly based on the weather and the alkaloid concentration. The most readily apparent signs of fescue toxicosis include reduced feed intake, weight gain, milk production and reproductive efficiency, as well as tissue necrosis and a rough hair coat. Decreases in productivity caused by fescue toxicosis are estimated to cost U.S. beef producers more than $2 billion annually (Kallenbach, 2015).

Absorption of alkaloids

Calculating the animal’s retention of ergot alkaloids is difficult due to biotransformation. Generally, it is estimated that 76–92% of consumed ergot alkaloids are absorbed, with the other 8–24% excreted in the feces. The math on alkaloid absorption and excretion doesn’t always add up, as alkaloids are broken down and/or biotransformed into numerous metabolites. Most alkaloids are ultimately excreted in the urine as lysergic acid.

Fescue alkaloids and microbiome shifts

An emerging area of research is the interaction between fescue alkaloids and the microbiome. Decreases in the Erysipelotrichaceae family and increases of Ruminococcaceae, Lachnospiraceae and Clostridiaceae, as well as abundances of Planctomycetes, Chloroflexi and Proteobacteria phyla have been reported for cattle grazing infected fescue. Fescue seed extract, when added to in vitro fermentations, led to increased populations of tryptophan-utilizing bacteria. Considering the tryptophan base of ergot alkaloids, this increase likely indicates an up-regulation in detoxification capacity. The characterization and identification of the three isolates with the highest conversion abilities found that all three were gram-positive, spore-forming rods that produced ammonia from tryptophan, classified as Clostridium sporogenes.

Receptor-binding of fescue ergot alkaloids

Due to the structural similarity of ergot alkaloids and serotonin, dopamine, norepinephrine and epinephrine, several receptor types in numerous tissues are affected during fescue toxicosis in cattle. This results in a wide range of effects on physiology and metabolism. As more research examining the underlying mechanisms is completed, the connections between ergot alkaloid receptor-binding and animal performance grow more complex.

Individual animal sensitivity to infected fescue is affected by:

• Environmental conditions.
• The density of the receptors.
• The capacity for liver and ruminal degradation.
• Other genetic factors.

Fescue's effect on weight gains

Ergot alkaloid-induced vasoconstriction reduces heat dissipation, resulting in a variety of physiological fescue toxicosis symptoms in cattle, including an increased respiration rate and elevated core body temperature. Ultimately, this leads to lower weight gains — which is generally known as the summer slump, as animals spend less time grazing as a result of standing in the shade or water to cool off. In colder months, fescue-associated vasoconstriction combines with thermoregulatory vasoconstriction, resulting in tissue death in the extremities, which is commonly known as fescue foot.

Ergot alkaloid consumption also leads to:

• The thickening of the medial layer of blood vessels
• Endothelial cell damage
• Vascular stasis
• Thrombosis
• Ischemia
• Changes in blood pressure, among other cardiovascular effects

Fescue's effect on rumen fill

The frequency and amplitude of the ruminal contractions, as well as changes in eating patterns due to fescue toxicosis in cattle, combine to affect rumen fill, passage rates and intake.

• Vasoconstriction also reduces blood flow to the rumen, decreasing VFA absorption.
• Increased rumen fill provides a negative feedback loop, exacerbating reduced intakes.
• While the total tract digestibility of the feeds is generally unchanged, these alterations work in concert to reduce nutrient availability, contributing to the reduced growth rate frequently observed in cattle grazing fescue.
• Added to this are the effects of alkaloids on circulating serotonin levels, the hypothalamic center and tryptophan-related satiety.

Fescue's effect on energy metabolism

Ergot alkaloids affect energy metabolism primarily when alkaloid intakes are high and during heat stress. Growth differences in cattle during fescue toxicosis are most likely the result of reduced intake, as no differences in retained energy or energy partitioning were caused by alkaloid ingestion when feed intake was equal.

• When fed near maintenance, cattle had lower basal metabolic rates.
• At higher feeding rates, maintenance energy requirements increased.
• When combined with observed increases in fat loss and a higher capacity for gluconeogenesis in the liver, this indicates the prioritization of energy (when available) toward elevated respiration, thermoregulation and alkaloid detoxification.

Economic losses due to fescue toxicosis

As much as 75% of the economic losses attributed to infected tall fescue pastures are related to decreased calving rates.

For cows:

• Alkaloid consumption reduces the circulating levels of several hormones important for reproductive efficiency, including progesterone and estradiol.
• Changes in ovarian follicle development, oocyte quality and luteal function have been reported.
• When combined with vasoconstriction to the uterus and ovaries, it is no surprise that reductions in reproductive efficiency are seen in cows grazing infected fescue.
• There is speculation that vasoconstriction in the umbilical cord contributes to low birthweights and diminished fetal development.

On the bull side of the equation, research indicates that ergot alkaloids may:

• Affect sperm count.
• Increase the occurrence of abnormal sperm.
• Alter motility, especially during the summer months.

Fescue's effect on milk production and calving

The structural similarity of ergot alkaloids to dopamine results in reduced prolactin secretion from the anterior pituitary gland. Further, changes in gene expression in the mammary glands of cattle consuming fescue indicate alterations in their lipid metabolism and small molecule transport. Altogether, these changes translate to reduced mammary development and lower milk production. Similar changes in lipid metabolism can be seen in reduced levels of circulating cholesterol and the occurrence of fat necrosis (lipomatosis), and in some cases of long-term alkaloid exposure, these fatty masses can cause digestive issues and dystocia. 

Fescue's effect on hair coat and immune function

Reduced prolactin also leads to the rough hair coat that is often observed in cattle grazing infected fescue. Originally thought to be a retained winter hair coat, it is now known that low prolactin levels increase hair growth rates. As prolactin is a co-factor in humoral immune function, the long-term grazing of infected fescue can lead to depressed levels of immunoglobulins. However, as nutritional levels also affect immune function, more work needs to be done to determine whether altered immunocompetence is a direct result of ergot alkaloid consumption or a secondary effect of a diminished nutritional status. While there is no true fescue toxicosis treatment for cattle, there are ways to mitigate the challenges that fescue presents through management, nutrition and feed additives.

References and Additional Reading

Fribourg, H. A., D. B. Hannaway, and C. P. West (ed.) 2009. Tall Fescue for the Twenty-First Century. Agron. Monog. 53. ASA, CSSA, SSSA. Madison, WI. 540 pp. Also (http://forages.oregonstate.edu/tallfescuemonograph).

Kallenbach, R. L. (2015). BILL E. KUNKLE INTERDISCIPLINARY BEEF SYMPOSIUM: Coping with tall fescue toxicosis: Solutions and realities. Journal of Animal Science, 93(12), 5487-5495.

Mayberry, K. J. (2018). Evaluation of Genetic Resistance to Fescue Toxicosis in Purebred Angus Cattle Utilizing Phenotypic Variables, Calf Performance and Cytokine Response. Thesis, North Carolina State University.

Melchior, E. A., & Myer, P. R. (2018). Fescue toxicosis and its influence on the rumen microbiome: mitigation of production losses through clover isoflavones. Journal of Applied Animal Research, 46(1), 1280-1288.

Poole, R. K., & Poole, D. H. (2019). Impact of ergot alkaloids on female reproduction in domestic livestock species. Toxins, 11(6), 364.

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With the numerous health and environmental challenges disrupting the pig industry at present, the summer heat is one seasonal condition that pig farmers cannot afford to let stifle their profitability. Heat stress can take a serious toll on pig performance, especially in breeding herds and finisher pigs. Heat and wide fluctuations in temperature are often immensely stressful for the animals, resulting in diminished performance, health problems and, eventually, economic losses for the farmer.

Why are pigs so sensitive to heat stress?

Pigs are extremely sensitive to changes in temperature because they do not have functional sweat glands and, therefore, do not have a way of efficiently cooling themselves. In addition, pigs have relatively small lungs for their body size, making it difficult for them to remove excess internal heat.

“Even during the hottest time of the day, pigs are still producing additional body heat from eating and moving around the barn,” said Russell Gilliam, U.S. swine business leader for Alltech. “Since pigs have few sweat glands, cooling off by perspiration is not much of an option. Respiratory rates begin to increase at around 70° Fahrenheit, and with high humidity, it becomes difficult for pigs to find relief from the heat on their own.”

Temperature fluctuations that continue from the summer into the fall season produce additional challenges. Wide variations in temperature between night and day can compound the stress that the animals already experienced as a result of increased temperatures.

What are the symptoms of heat stress in pigs?

One of the negative effects of heat stress is reduced feed intake. When pigs eat less, they convert less feed into muscle, thus reducing average daily gain (ADG) and potentially increasing their days to market. In turn, this can also lead to a heightened risk of health challenges and, ultimately, additional costs for producers.

Other symptoms include:

• Increased respiratory rate (panting)
• Excessive water intake and increasing loss of electrolytes
• Reduced activity
• Lying stretched on the floor, often separated from others

6 management strategies to reduce heat stress in pigs

Although stress cannot be completely avoided, the goal should be to minimize it as much as possible. Below are some quick tips for reducing heat stress and its negative effects:

1. Control the temperature, and make sure the temperature only shifts a few degrees in the barn.
2. Ensure that each pig has enough space and ventilation.
3. Coincide feeding times with the cooler parts of the day (e.g., earlier or later in the day).
4. Provide pigs with unlimited access to fresh and cool drinking water.
5. Move and transport work pigs early, keep them in groups and let them set the pace. Spend time with them prior to the move to ease their stress.
6. Tailor their diets to include technologies that will support them during stress.

Balancing temperature, ventilation and humidity

When pigs are kept at temperatures above their comfort zone, feed intake is sure to decrease, as are daily gains. In modern swine barns, pigs are at a greater risk of experiencing heat stress than cold stress. Ensure that all fans, sprinklers, cool cells and other cooling equipment are adequately maintained so that they will function properly during the hot summer months.

In addition, make sure that your barn is properly ventilated to provide pigs with an optimal environment. Even if the thermostat reading falls within the pigs’ comfort zone, what they are actually experiencing may still be stressful.

Effective temperature is a concept similar to wind chill and heat index. For example, 60°F is a favorable temperature for a 125-pound pig. However, 60°F combined with a high air speed (e.g., 100 feet per minute) would be cold and, consequently, the pig would be forced to divert energy away from growth to maintaining its body temperature. Chart 1 shows how wind speed affects temperature.

Chart 1: Effects of wind speed on temperature

The temperature within the barn needs to be adequately adjusted to account for the additional heat production from the growing pig. For every 60–80 pounds of gain, the pig will produce an additional 200 Btu of heat every hour, so the cubic feet per minute (CFM) must be properly adjusted to account for the increasing heat production.

Chart 2: Recommended ventilation rates, CFM per pig

Effects of humidity

Humidity is also an important indicator of proper ventilation. During warmer months, when the outside temperature exceeds the set point, increasing ventilation rates will not decrease humidity in the barn because warm air has a higher water-holding capacity than cooler air. Pigs can develop heat stress at much lower temperatures when the humidity is high, so humidity, along with temperature, needs to be carefully regulated in the barn. It is recommended to operate at a relative humidity of 65% or less, as this level of humidity will decrease condensation and wet floors in the barn.

Tailoring diets to support stress

Data has shown that offering pigs a combination of organic acids, electrolytes, enzymes and probiotics, such as those included in Acid-Pak 4-Way®, can support young animals during times of stress. Organic acids promote probiotic growth in the gut, and enzymes can help enhance intake and digestibility. Electrolytes keep the animal hydrated, especially in times of heat stress.

Addressing heat stress and being prepared for its effects can have a major impact on the performance and overall value of your pigs when you take them to market. It can also help reduce the cost of added days on feed and additional health costs. In times of stress, pigs can be more susceptible to disease and health challenges. It is essential that your pigs’ nutrition is bolstered by technologies that build their natural immunity.

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While the northern hemisphere has been experiencing the wrath of the polar vortex and record cold temperatures, the southern hemisphere has been on the opposite end of the spectrum, dealing with sweltering heat. Fortunately, there are generally simple ways for humans to escape the uncomfortable effects of extreme weather — but the same cannot be said for horses, who must expend substantial energy in an effort to keep cool as temperatures rise.

While you can still enjoy equestrian pursuits on relatively warm days, you will want to take extra precautions to ensure that your horse stays healthy and safe in the heat. Equine heat stress is a serious concern, and although it may first manifest in seemingly minor ways, such as poor performance, it can quickly escalate to potentially fatal heat exhaustion and stroke. As such, it is highly important to develop an understanding of the stages and signs of heat stress so that you can take immediate action if you observe them in your horses.

Stage 1:

• The horse may sweat profusely and exhibit a heightened body temperature (the normal equine body temperature ranges from 99–101° Fahrenheit or 37.2–38.3° Celsius).
• The heart rate elevates significantly. A horse’s normal resting heart rate is within 30–50 beats per minute, and a pulse rate of 50 or higher is generally a cause for concern.
• You can also check for signs of dehydration by grasping a fold of skin at the point of the shoulder and releasing it. If the horse is well-hydrated, the skin should snap back quickly (in under one second). Generally, the longer the skin takes to flatten, the more dehydrated the horse. However, it’s important to already know what your horse’s normal skin elasticity is, as this can vary.
• Capillary refill time can also be used to measure hydration. To check this, press lightly on the horse’s gum just above an upper incisor and observe how long it takes for its normal pink color to return; two seconds or less is normal.

Stage 2:

• Rapid, shallow breathing may be apparent. For reference, the normal respiratory rate for a resting adult horse is between eight and 15 breaths per minute. 
• The horse’s behavior can become uncooperative; it may frequently kick or randomly shake its head. Minor gait abnormalities may also be observed.
• You may also detect an irregular, fluttery heartbeat or witness tying-up (i.e., muscle cramping as the result of the massive contraction of the muscle groups along the horse’s back and rump).
• Sweating has likely ceased, but the skin remains hot to the touch as body temperature rises. A body temperature between 104–108° Fahrenheit (or 40–42.2° Celsius) indicates a heightened risk of danger for the horse, as heat exhaustion is beginning to set in.

Stage 3:

• The horse will hang its head low and appear extremely unhappy. It may also clearly be struggling to breathe normally, taking slower and deeper breaths, which is known as second-phase panting.
• The pulse will remain heightened but also weak and potentially irregular.
• Gut sounds are reduced or absent.
• The horse may appear confused and make increasingly clumsy movements.

Stage 4:

• The consequences and effects of prolonged heightened body temperature (in excess of 106–108° Fahrenheit, or 41.1–42.2° Celsius) may lead to heat stroke.
• The central nervous system will begin to shut down, which can lead to:
  • Severe stumbling or difficulty moving
  • Volatile behavior
  • Increasingly confused mannerisms
  • Collapse
  • Convulsions
  • Unconsciousness or comatose state
  • Death

So, what can you do if your horse appears to be suffering from the ill effects of heat stress?

• Walk the horse out to encourage circulation and to bring heated blood to the surface of the skin for cooling.
• Let the horse drink its fill. A hot horse should take in as much water as it needs to replace what is being sweated out. Cold water is fine — the idea that letting a hot horse drink cold water can cause colic and muscle cramping is simply a myth.
• Splash or spray cold water directly onto the horse to aid with evaporative cooling. Despite what you may have heard, putting cold water on hot muscles does not constrict blood vessels and lead to cramping. Do make sure to frequently scrape off the water, because it will warm up quickly on the horse’s body. Repeat this process until the skin feels cool to the touch and the horse’s breathing appears to have returned to normal.

If the horse’s behavior and drinking habits have not returned to normal within one hour, or if you witness more dramatic signs of heat stress within that window of time, call your veterinarian immediately. Intravenous hydration and other medical measures may be required to prevent potentially irreversible effects or loss of life.

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Tall fescue (Lolium arundinaceum) is a cool season, perennial bunch grass native to Europe. Since its introduction in the early 1800s, it has spread widely throughout the southeastern and lower midwestern United States. Due in large part to its tolerance for heat and low-quality soils, and its adaptability to a wide range of conditions, tall fescue is now grown on more than 37 million acres of land in the U.S. (Thompson et al., 1993), and it is estimated that more than half of these fields are infected with the fungal endophyte Epichloë coenophiala (Jones et al., 2004). This endophyte provides positive characteristics to the plant, but the secondary metabolites (ergot alkaloids) produced by the endophyte have negative consequences to animals grazing on infected fescue.

The positives and negatives of fescue utilization

Symptoms of tall fescue toxicosis in cattle

The pathology of cattle consuming infected tall fescue can vary greatly depending on the weather and alkaloid concentration. The signs most readily apparent to producers include reduced feed intake (up to 50 percent) and weight gain, decreased milk production, reduced reproductive efficiency, tissue necrosis and a rough hair coat. Collectively, this range of conditions is known as “fescue toxicosis.” The decrease in productivity caused by fescue toxicosis has been estimated to cost U.S. beef producers more than $2 billion per year due to reduced growth, diminished reproductive efficiency and market discrimination because of unthrifty appearance (Kallenboch, 2015). 

Consumption of the ergot alkaloids in endophyte-infected tall fescue results in widespread vasoconstriction in cattle. This reduces the ability of the animal to dissipate heat, resulting in a variety of physiological symptoms, including increased respiration rate and elevated core temperature. This reduction in tolerance to heat leads to less time spent grazing and reduced weight gains, generally called “summer slump.” In colder months, the vasoconstriction from fescue can combine with natural vasoconstriction related to thermoregulation, resulting in tissue death in extremities such as ear tips, tails and feet, commonly known as “fescue foot.”

The vasoconstriction also reduces blood flow to the rumen, decreasing volatile fatty acidy (VFA) absorption. Consumption of ergot alkaloids also reduces passage rates of digesta from the rumen, likely by reducing rumen motility. These alterations work together to reduce nutrient availability, contributing to the reduced growth rate frequently observed in cattle grazing fescue. 

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Cows exhibit heat stress in many ways, and the impact can be seen in both the short and long term. Understanding heat stress is critical for producers managing herds in warmer, more humid climates or farms located in areas that experience intense heat spells in summer. There are appropriate management practices to help herds avoid some of the heat and strategies that work with the animal to help a herd manage stress during the summer months.

Often the simplest solutions for heat stress are cheap, only requiring good herd management. Here are 10 heat stress management tips to help your herd stay cool.

1. Provide shade. 

Cows will experience lower respiration rates, decreased body temperature and less aggression when provided with adequate shade.

2. Clean water tanks. 

Cows can drink 30–50 gallons of water on a normal day, but that number can double when cows experience heat stress. By providing fresh, clean water, cows will drink more and stay hydrated.

3. Feed during cooler hours. 

Cows don’t like to consume hot feed, and TMRs are prone to heating when left out. By unloading, mixing and feeding in the morning, cows can eat before the feed gets hot and ruminate during the warmer hours of the day.

4. Watch for inconsistent manure. 

Decreased rumen fermentation efficiency occurs when the cow is experiencing heat stress, leading to lost nutrient utilization. Reformulating the ration can help achieve optimum nutrition potential during phases when dry matter intake drops. 

5. Ensure access to feed. 

Depressed intake is common during heat stress periods. By providing feed at all times, cows will eat small amounts throughout the day to reduce thermal heating from large meals.

6. Use sprinklers, soakers and fans. 

Observe where the cows are congregating. Why are they there? Is a sprinkler out elsewhere in the barn? Are the fans providing air flow? Even if you have cooling equipment, ensure it is optimally located and functioning properly.

7. Reduce time in holding pens. 

The key issue with heat stress is that the environment is too warm to dissipate the heat coming from the cows. Keeping cows in close holding pens for prolonged periods of time reduces space and airflow. 

8. Don’t lock up during midday. 

Cows are smart and will move away from areas that are too hot, but only if they have the space to do so. By allowing them to move during the hottest time of the day, you allow them to move to cooler locations in the barn.

9. Feed more digestible high-quality forages. 

Since cows are prone to eat less when hot, efficiently accessing nutrients is essential to health and production. First cutting or fermented forages provide energy without requiring as much rumination as more fibrous feeds, reducing provisional heating.

10. Utilize a yeast culture additive. 

Yeast cultures have been found to stimulate the bacteria in the rumen responsible for both fiber digestion and acid removal. This will aid in improved fermentation efficiency and prevent acidosis, which can decrease body temperature.

A happy cow makes for a productive cow. Cow comfort is important year-round, but it’s a much bigger challenge in seasons of heat. Proper management of feed, water and shelter can help your herd stay comfortable and productive. Learn more about designing your barn for cow comfort year-round in Tom Lorenzen’s article “Designing dairy free stalls for cow comfort.”  

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The following is an edited transcript of Tom Martin's interview with Tom Lorenzen, on-farm dairy specialist with Alltech. Click below to hear the full interview:

Tom:                          The heat and humidity of summer can take a substantial toll on herd health and productivity. Understanding heat stress is critical for producers managing herds in warm, humid climates. Alltech’s Tom Lorenzen is an on-farm dairy specialist with a focus on dairy audits and education through milking technician schools and presentations on milk quality. He's with us to talk about nutritional approaches to the prevention of heat stress during the summer months. Thanks for being with us, Tom.

Tom L:                        Thank you.

Tom:                          First, for reference, can you define the characteristics of a heat wave?

Tom L:                        Well, that's a great question. The people in Wisconsin had almost 20 to 30 inches of snow this past weekend, so they’re probably not going to talk about a heat wave! But we're talking about heat stress with the dairy cow. That's when the environmental conditions are out of the optimal range for the cow, which is between 25 and 70 degrees Fahrenheit.

Tom:                          What factors determine when it’s severe? How do you know when it's really bad?

Tom L:                        Air temperature, relative humidity and air movement, solar radiation —they all affect heat stress. Under mild heat stress, we see cows breathing rapidly. As the temperature increases or the stress increases, we see the breathing rates increase in cows, too. I always say to stop, look and listen to your cows. When I watch the cows and I see that their mouths are wide open and they’re panting rapidly, you can be assured that they’re under heat stress. Cows can reduce their heat stress a little bit by sweating, but they sweat about 1 percent compared to humans.

Tom:                          What are the effects? What happens to the cow when they come under stress like this?

Tom L:                        We see cows panting and increased drooling. This reduces the amount of saliva going into the rumen, which will have a negative effect on the buffering of the rumen. This can lead to acidosis. We will see reduced feed intakes, reduced rumination and the bottom line: reduced milk yield.

Tom:                          Are there regions that tend to suffer more periods of heat stress than other areas?

Tom L:                        Yes. That’s a great question. In the United States, we're going see more heat stress with higher temperatures and humidity if you’re looking at the southeast parts of United States, including Florida, Alabama and Georgia.

Tom:                          What can happen to levels of milk production when this happens, especially during prolonged periods of heat stress?

Tom L:                        When cows suffer from heat stress, the first thing we’ll notice is reduced feed intake. They just don't go to the bunk. When we see that happen, we see reduced milk yield, as much as 8 pounds of milk per day.

Tom:                          Do you see effects on reproduction?

Tom L:                        Definitely. It affects fertility and reproduction. It leads to longer lactations or more open days. We see a compound effect where there are other health issues in regard to heat stress.

Tom:                          There are some obvious mechanical means of reducing heat stress: fans, sprinklers, those sorts of things. What about nutritional strategies?

Tom L:                        The first one I’m going to talk about is water. Water is very, very important. Water makes up about 85 percent of the content of milk. So, as the temperature goes up, so does the cow’s water requirement. Cows can drink up to 50 percent more water when the temperature and humidity index rises. Intake can go from 20 gallons to about 32 gallons of water per day when the temperature gets above 86 degrees Fahrenheit.

                                    One of the big things I notice when I’m working with dairy is making sure the water troughs are clean and scrubbed daily in order to provide adequate water for consumption. If we can’t drink it, how can we expect the cows to drink it? We need to make sure that we provide adequate water space — 3 feet of available water for at least 10 to 15 cows is important.

Tom:                          Another factor in nutritional strategies would be energy. Why is it essential to increase the energy density of the diet during heat waves?

Tom L:                        As the temperature increases, the cows decrease their feed intake. This decrease in feed intake can result in less nutrient absorption. So, by increasing energy density of the diet, we can help maintain energy requirements. A good feed source for energy is bypass fat in the diet.  

Tom:                          Let's move on to protein. How is protein intake influenced by heat stress?

Tom L:                        Like everything else, when we increase heat stress, we see less dry matter intake, which means lower protein levels during this period. This will give us a negative nitrogen balance. This leads to a dramatic decrease in milk yield, immune responses and reproduction. One way to help mitigate the decline in protein ingestion is to increase protein density in the ration as well as to make sure we provide a ruminal-digestible protein source.

Tom:                          I understand that during these periods of high heat, it’s really important to maintain fiber levels in the diet. It’s crucial, but there is this catch: the digestion of forages creates more heat. How should that conflict be mitigated?

Tom L:                        During heat stress conditions, there’s a greater risk for rumen acidosis due to slug feeding and decreased intake. To reduce this risk, maintaining fiber levels in the diet is crucial. However, forages have a higher heat increment, so the quality and degradability of the forage should be monitored. Good-quality forages that will be quickly digested in the rumen will contribute to the health of the rumen and will also help maintain milk production with a minimum impact of increased caloric diets.

Tom:                          And, finally, minerals. What are the roles of minerals in helping cows combat heat stress?

Tom L:                        As I mentioned, heat stress causes increased salivation. Saliva is one of the most important buffers that the cow creates on her own. To provide another buffer, we look at increasing sodium, potassium or magnesium to help reduce the stress during this period.

Tom:                          What management tips can you offer producers as they prepare for the hot summer months?

Tom L:                        We need to provide ample clean water at all times. Another important part is providing fans and sprinklers to help cool the cows. We also need to provide shade. One of the biggest challenges that I run into on a dairy is overcrowding. If we’re overcrowded, the cows are not going to have ample room to eat and lay down. These are all important things. Lastly, and very importantly, we want to provide some of our checks that we do during the week such as pregnancy checks, or if we’re going to move cows, or breed cows, we want to do that early in the morning to reduce cow stress.

Tom:                          Thank you, Tom. We appreciate your time.

Tom L:                        Have a great day.

Tom:  Tom Lorenzen is an on-farm dairy specialist for Alltech

Click here to download a free dairy heat stress poster.

I would like to learn more about improving efficiency on my dairy. 

Biostimulants enhance nutrient assimilation and plant development. They are becoming a popular crop input in many countries around the world for several reasons.

Benefits to using biostimulants on your farm

1. Biostimulants assist in combating the effects of environmental stresses.

Biostimulants promote enhanced germination and root development, leading to increased vigor and greater stress resistance. An enhanced root system promotes more efficient nutrient and water uptake and translocation throughout the growing season.

2. Biostimulants increase grain fill and quality.

Promoting growth and improvinga plant’s metabolism can benefit overall plant growth and health. In addition, providing a catalyst at specific developmental stages can lead to increased yield, improved uniformity and overall crop quality.

3. Biostimulants encourage plant growth.

Biostimulants generally operate through different mechanisms than standard fertilizers and provide essential nutrients for plant metabolism that stimulate plant growth. These metabolic pathways upregulate gene expression that can have an effect on cell division and sizing, root and shoot growth, and reproductive development and timing.

Your agronomist or crop advisor can give you more information on incorporating biostimulants into your current crop management program.

How does Dan Donavan of Murphy and Sons increase yields and improve the quality of his tomatoes which are destined for restaurants like Subway, and What-A-Burger? He looks under the soil at root structure, of course, and that’s where Alltech Crop Science comes in.

The impact that heat stress can have on a herd, as we all know, can be substantial. When looking at a lactating herd, it is critical to find ways to minimize the effects of heat. But one vital area of the farm that is affected by heat is sometimes overlooked: calves can be extremely susceptible to higher temperatures due to their smaller body mass and higher respiration rate.

Calves and lactating cows experience heat stress at different levels. For a mature lactating animal, the level at which they begin to experience heat stress is at around 60 degrees Fahrenheit and is lower in humid environments. In contrast, calves start feeling heat stress around 75-80 degrees Fahrenheit. In the summer sun, calves look for relief in their hutches, but sometimes the hutch environment can be even hotter and more humid than the outside environment.

By managing the following three key areas, producers can ensure that their calves stay cool and healthy during the hottest time of the year.

Drink up: Keep calves hydrated

Though it might seem obvious, ensuring calves have an adequate water supply that is fresh and clean can be a key factor in helping to prevent dehydration. Dehydration can be particularly dangerous during times of gastrointestinal stress, which can hinder a calf’s rate of recovery.

Water acidifiers have been shown to increase water consumption because they make the water more palatable to the calves, which encourages them to drink more.

Shoo, fly — don’t bother the calves!

Hot temperatures go hand in hand with flies. It is extremely important to control flies in the calf’s environment, as flies are a main offender when it comes to transferring dangerous bacteria throughout the herd. Illnesses such as pink eye are known to be spread by flies. Recent research has also shown that flies can be carriers of some strains of Salmonella, which can show up later in life as a cause of mastitis at first lactation.

Common fly control methods include an Insect Growth Regulator (IGR) in the feed as well as treating and spraying around hutches with chemicals labeled to assist in fly control.

Easy, breezy temperature maintenance

Adequate ventilation is important for calves, especially if they are kept inside an enclosed area or barn. Some operations may have a more serious ventilation issue when using automatic feeders because the bedding can be more prone to moisture.

Ensuring the bedding remains clean and dry is critical to calf health and longevity. As temperatures rise, ammonia levels tend to rise as well, and wet bedding can pose a serious threat to calves as a result. Utilizing an ammonia binding product can be helpful.

De-Odorase®, a product from Alltech, is commonly utilized in calf barns to control ammonia issues.

Adequate ventilation is also important in the hutch. One key component to hutch ventilation is keeping vents open during the day, as hutches can get too hot if vents are closed. What many people don’t think about in the summer, though, is that hutches can also get too cold on cool evenings if the vents are not closed at night. This is particularly concerning in the summer because usually less bedding is used during this time, and a cold front can be hard on the less protected calves, especially when they are younger.

Heat stress can affect herds in many ways. Herd longevity and the future of operations depend on the health of calves, who rely on farm owners and managers taking the necessary steps to ensure they remain healthy during the summer. 

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