Maximising energy requirements in a heat stress scenario | UFAC-UK
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Preventing heat stress is vital for dairy farmers as it can affect cow’s dry matter intake, milk production, and pregnancy rates, ultimately costing them money.

Traditionally, UK temperatures do not tend to climb high enough to harm milk yields and overall body temperature in cattle. However, in recent years, evidence has suggested that even relatively low temperatures during the UK summertime can lead to depressed feed intakes, lower milk yields and reduced fertility. 

Dairy cows must maintain a constant body temperature of around 38.8°C to avoid suffering from heat stress. The comfort zone for dairy cows varies from 15 – 22°C. At temperatures below -15°C, the cow will increase its dry matter intake to keep warm and convert feed into energy for maintenance rather than milk production. At temperatures above 22°C, cows will increase their heat dispersion and limit heat production by reducing all activity and changing feeding patterns. 

If a cow fails to control its thermal balance, it becomes heat-stressed, and its feed intake and milk yield will decline. As the ambient temperature increases above 25°C, milk production can fall by as much as 20%. Fertility will also be affected, including an increase in embryonic loss.

Preventing heat stress is vital for dairy farmers as it can affect cow’s dry matter intake, milk production, and pregnancy rates, ultimately costing them money. Heat stress also increases lameness, disease incidence, days open, and mortality rates. 

What is heat stress?

Heat stress in cows is caused by moderate to high temperatures and high humidity. A high-yielding dairy cow generates about 2,000 watts of heat (20 times more than a man) and needs to dissipate it to the environment. At temperatures above 22ºC, cows cannot effectively dissipate their body heat. This results in increased energy requirement for maintenance, reduced feed intake, less milk production, decreased immunity, and poor fertility. Heat stress can occur both indoors and outdoors.

In this blog, we detail how to know if your dairy herd is suffering from heat stress, the symptoms, how to prevent it and how UFAC energy supplements can help maximise energy requirements and maintain body condition.

UFAC dynalac fat supplement packaging.

How do you know if your cow is heat-stressed?

Respiration rates

You can observe your cows’ body respiration rates at different periods throughout the day to see how they cope with the weather conditions. 

Looking at respiration rates in your dairy cows is the recommended measure of heat stress detection. Typically, respiratory rates for dairy cows range from 20 to 40 breaths per minute, 40 to 50 be aware of potential issues & over 60 is heat stress.

Physical appearance

Cows experiencing heat stress may not show any physical signs at all. However, some symptoms of heat stress include breathing with their mouths open and panting with their necks extended. They could also appear lethargic and may appear unsteady on their feet. 

Milk production 

Milk yields will decrease as the level of heat stress increases in your herd. Mild heat stress results in poor production. A decrease of about 1.2 kg per head per day under such circumstances is not unusual. Moderate to severe heat stress can result in a production decrease of about 4.1 kg per head per day, and severe heat stress can lead to less milk production of 4.5 kg or more per head per day.

Symptoms of heat stress to look out for

  • Increased sweating 
  • Panting 
  • Increased rectal temperature
  • Standing rather than lying down 
  • Reduced fertility
  • Reduced milk yield 
  • Differences in behaviour 
  • Crowding under shade 
  • Standing next to water 
  • Reduced feed intake 

Preventing heat stress

There are several ways that dairy farmers can help their cows manage their body temperature in hot and humid climates. 

Improve day-to-day feeding strategies on your farm.

  • Monitor temperatures and humidity
  • Increase ventilation 
  • Consider feeding twice a day or, if not feasible, feed in the evening
  • Remove rejected food 
  • Maintain feed freshness 
  • Ensure adequate supply of clean water 
  • Increase energy density of diet 
  • And finally, ensure feed is pushed up regularly to maximise intakes

Increase fat content to maintain energy

Unlike carbohydrates, fat is a ‘cool’ ingredient that bypasses the rumen fermentation thus less heat is released during the metabolism of fats compared to carbohydrates. This helps in reducing heat production and maintaining normal body temperatures. Furthermore, supplementing dairy cow ration with fats increases energy density of the diet, helping to compensate for reduced dry matter and energy intakes.

Provide good quality forage

When offered to your highest-yielding cows under heat stress, good quality forage with sufficient levels of physical effective fibre and Neutral Detergent Fibre (NDF) can help improve fibre consumption, maintain good rumen activity and minimise the risk of sub-acute ruminal acidosis (SARA) that is likely in hot weather.

Feeding yeast and rumen buffers

Yeast and rumen buffers can have a positive effect on rumen pH and reduce the risk of acidosis. If you’re already doing this, consider increasing fate rates or targeting high-risk animals.

Water provision

Cows typically consume about 4.5 litres of water per litre of milk produced, and those suffering from heat stress will drink 30% – 50% more water than normal. This leads to more traffic at the water trough and expose some herd members to being bullied away from drinking.

The quantity and quality of water supplied to the dairy cow often receives little attention. Contamination leads reduces water intake. It is also worth noting that to optimise feed consumption in the summer, water temperature must range between 15 to 20°C.

How UFAC-UK can help

UFAC has developed a range of highly palatable products that are designed to help cows meet energy requirements during heat stress scenarios. UFAC nutritional supplements can help your dairy cows recover faster from heat stress when fed at the right times.


envirolac is a unique product that contains omega-3 fatty acids along with glycerine and has a buffering effect to help optimise rumen pH and during heat stress. It is designed for high-yielding dairy cows to increase dietary energy density while optimising rumen fermentation and priming liver function to increase milk yield and constituents and improve cow health and fertility.


dynalac is a proven fat supplement for high-yielding dairy cows. Its unique combination of fatty acids helps meet the energy needs of milking cows while supplying the specific nutrients required for optimum performance when intakes are suppressed. dynalac contains omega-3 fatty acids for better cow fertility and immune function. The buffering aspect of fibre component of dynalac is also important during heat stress when lactate-producing bacteria are reduced due to lowered rumen pH, potentially negatively affecting milk production.


Typically fed to dairy cows in transition or early lactation to reduce negative energy balance, glycerene helps achieve high dry matter intakes while minimising body condition loss by supplying glucose to the liver to drive milk volume.

glyco buf

glyco buf has a buffering effect designed to improve rumen health in high-yielding, transition, and early lactation cows. It optimises rumen fermentation and improves energy supply, leading to improved dry matter intake, lower body condition loss and fewer metabolic disorders, lowered risk of SARA. glyco-buf is also formulated to improve milk yields and constituents.

Contact us

Interested in learning more about UFAC products? Fill out the form below, and a member of our team will be in touch with more information, or contact our Regional Business Managers directly.

Steve Willats

M: 07827 249157

South West and Wales 


Richard Lapthorne 

M: 07788 963 487

North England and Scotland 


James Hastings-Molyneux 

M: 07538 763 832

South East and Midlands