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Summer Stress: Keeping Your Cows Healthy All Summer Long

Summer Stress: Keeping Your Cows Healthy All Summer Long

High temperatures and humidity are tough on cattle and productivity. And worse, stress can compound in animals, as pink eye, summer pneumonia, and flies all start to threaten cattle performance.

According to Iowa State University, once temperatures reach above 80 degrees Fahrenheit, beef cattle endure physiological stress dealing with their heat load.

Heat abatement, or the reduction of heat stress, along with managing other summer stressors, is critical for beef producers to minimize production losses and keep cattle healthy all summer long.

Preparing for Heat Stress in Cattle

Cattle sweat very little - about 10% of the human rate. To cool themselves, cattle will dissipate heat through respiration or panting, radiating heat from their bodies with vasodilation (pushing blood to the body's surface for heat removal) and reducing feed and forage intake.

Cattle generate heat in their rumen during fermentation, which causes core temperatures to rise even more. They also typically congregate at water troughs or under trees during the summer months, making it hard for heat to escape, escalating the impact of heat stress.

Cattle’s ability to dissipate heat depends on:

  • Air temperature and relative humidity

  • Wind speed

  • Thermal radiation

  • Energy level in the feed ration

According to the Journal of Dairy Science, economic losses from heat stress to the United States cattle industry are estimated at more than $370 million annually. The dairy industry experiences more than double that loss at $897 million.

What Are the Signs of Heat Stress in Cattle?

Cattle experience visible and internal signs of heat stress as they attempt to dissipate heat.

Visible Signs of Heat Stress

Internal Signs of Heat Stress

​Open mouth breathing and panting

Productivity stops as energy is diverting to returning the body to homeostasis, decreasing performance


Inflammation and immune activation

Decreased feed intake and increased water intake

Lower reproduction rates

Decreased activity, lying down

Leaky gut

Reduced average daily gain (ADG)

Increased insulin levels

Agitation and restlessness

Higher mortality

The USDA states that production losses have already begun once cattle start experiencing visible signs of heat stress.

How to Manage Heat Stress in Cattle

Cattle producers can prepare for and combat heat events with a combination of management practices and tools such as:

  • Ensuring cattle have access to plenty of fresh water. Add more tanks before a heat event to help alleviate congregation around the main water tanks.

  • Using droplets, not mist. Make sure the droplets of misters are large, not small. If the droplets are too small, they can create added humidity, worsening heat stress.

  • Providing shade. Shade structures should be open and 8 to 14 feet tall to allow for proper ventilation. They should provide between 20 and 40 square feet per animal depending on animal size.

  • Fresh feed. Heat also impacts feed quality and increases the growth of bacteria, mold and yeast, making feed less appetizing to cattle. Ensure cattle have fresh feed in a feedyard setting.

  • Supporting their immune system. Heat stress equals gut stress. More than 70% of the immune system is contained in the gut. As heat stress erodes cattle's immunity and gut health, which can lead to disease challenges and performance losses, it is essential to support their immunity. Research shows that feed additives using essential oils and capsicum can help boost immunity, provide antioxidant support and help cattle reduce the impact of heat stress.

Controlling Summer Pink Eye in Cattle

Beef producers know the threat of pink eye is more prevalent in the summer.

Also known as infectious bovine keratoconjunctivitis (IBK), pink eye is a highly contagious disease that severely impacts productivity and is incredibly painful to cattle.

According to the University of Wisconsin, pink eye is primarily caused by the bacteria Moraxella bovis, which produces a toxin that attacks the eye. It is commonly understood that Moraxella bovis is the cause of traditional IBK or summer pink eye.

What Causes Pink Eye in Cattle?

Several things can predispose cattle to pink eye. The eyes have natural defense mechanisms to thwart infection and damage. However, eye irritants or trauma allow pathogens to pass through the eyes’ defenses and reach the cornea.

Predisposing factors associated with pink eye:

  • Face flies

  • Dust and sand

  • Weeds, tall grass and stalks

  • Other animals, overcrowded from heat stress and tails swishing from flies

  • Physical hazards like barbed wire or trauma during handling and transport

Pink eye in cattle

Pink eye occurs in stages as the eye tries to repair itself. Stage two occurs when blood vessels spread throughout the cornea to heal it. The eye becomes bright pink, explaining how the term ‘pink eye’ was derived.

What’s the Impact of Pink Eye?

Pink eye in cattle

The University of Illinois estimates the cost of pink eye to the U.S. cattle industry at more than $150 million per year due to decreased weight gain, milk production, treatment costs and permanent scarring to the eye that reduces sale price. Recent studies show a 17 – 65 lb. weight loss from pink eye, with treatment costs exceeding $100 per incident.

How to Manage Pink Eye in Cattle

Many beef producers use pink eye vaccines with varying levels of success

in the summer months. Yet, the best way to reduce the incidences of pink eye is to manage the associated predisposing factors. Face flies can carry pink eye from animal to animal, so fly control methods are critical. Additionally, ensuring animals are not overcrowded or near hazards, reducing heat stress and handling them as little as possible can help. If pink eye cases are discovered, immediately isolate cattle from the herd and treat them until the infection is gone.

Preventing Summer Pneumonia in Calves

Preventing Summer Pneumonia in Calves

Summer pneumonia in nursing calves is another challenge for beef producers to watch out for. This problem can occur quickly and unpredictably, with the first sign often being sick or dead calves.

The University of Nebraska identifies summer pneumonia as a respiratory disease in pre-weaned calves on pasture. While the direct cause of summer pneumonia is unknown, researchers and veterinarians have found a few direct correlations between outbreaks and these varying factors:

  • Poor colostrum quality from cows lacking in nutrition

  • Reduced immunity in calves after colostrum antibodies wane and the calves’ natural immune system takes over

  • Hot and dusty conditions in late summer break down the calves’ natural defense mechanisms in the lungs

  • Temperature swings

  • New older calves being introduced to the herd and shedding viruses

  • Poor mineral nutrition in cows and calves

Some of the symptoms of summer pneumonia do not always include breathing issues or respiratory problems. Symptoms can also be high fevers, droopy ears, sluggishness and having difficulty keeping up with the herd moving from pasture to pasture.

To prevent summer pneumonia, vaccines should be administered before calves are turned out to pasture. Additionally, providing a high-quality mineral year-round for cows and calves is critical. This will help enhance the colostrum quality of cows and strengthen calf immunity.

If outbreaks of summer pneumonia occur, antibiotics and anti-inflammatories are proven successful if caught early on. Always consult with your veterinarian before administering.

Managing Summer Flies and Ticks

Managing Summer Flies and Ticks in Cattle

Small but irritating, flies are a pest to everything in the summer months, especially cattle.

The most common flies that impact beef cows are horn flies, face flies and stable flies. Horn flies are small, black, bloodsucking flies known to bite cattle between 20-30 times per day per fly. Stable flies are painful blood feeder flies that are more irritating to cattle and mainly attack the front legs. Face flies are nonbiting but are known for contributing to the spread of pink eye in cattle.

According to the Journal of Entomology, U.S. beef producers' economic loss from flies ranges from $1-2 billion annually.

The goal of fly control is to keep fly populations below the economic threshold of the cow, which means that instead of 1,000-4,000 horn flies per cow, it’s suggested to keep flies below 200 per cow with fly control methods.

How to Manage Flies and Ticks in Cattle

Fly resistance is a growing concern in the cattle industry. As flies overcome our fly control methods, it is recommended to use multiple fly control methods.

Various fly control programs exist today, including:

  • Ear tags

  • Sprays

  • Oilers

  • Dust-bags

  • Vet guns

  • Feed additives

New research shows that adding garlic to cattle mineral is another effective strategy for fly control and ticks. A study in Canada found that adding garlic to mineral helped reduce flies by 50%.

Overcome Summer Health Challenges with Ralco

With calving season over and breeding season underway, summer is a little more relaxed for ranchers, but it can come with challenges and surprises. Ralco can help.

For the last 50 years, Ralco has been helping beef producers keep their cows and calves focused on converting nutrients to growth instead of waste. From high-quality mineral to essential oil feed additives and animal health products, Ralco has solutions to keep your cattle healthy and focused on production all summer.

To learn more about heat stress and what mineral is best for your herd, give us a call at 507-337-6916 or email


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