Heat Stress Prevention in Poultry

Small chick showing signs of heat stress with open beak breathing.

Technical Corner

Latest insights and information from our Technical Director

By Nigel Strain

Here in the UK and Europe summer has finally arrived, and whilst we all enjoy some nice, warm weather we must also be mindful of the challenges within our poultry houses’ environment. 

Small chick showing signs of heat stress with open beak breathing.

Record-breaking temperatures, as well as record-breaking production year on year, means that removing excess heat from our broilers is an increasing challenge.

Signs of heat stress

80% of the heat within a broiler house is produced by the birds themselves (metabolic heat) and birds have 3 methods of losing heat – conduction, convection, radiation. Once the body temperature climbs above the broilers’ normal range (40-42C) they will begin to show early signs of heat stress such as wing-spreading and slow panting and this will progress to faster panting as their body temperature increases further. If it reaches 45C and above, there is a high probability of death. It is therefore crucial that we manage to balance bodyheat production and bodyheat loss during periods of warm weather to protect the birds’ welfare and maintain performance.

Remove excess heat 

It can become difficult for a fully feathered broiler to lose enough of its body heat once the ambient temperature reaches above 27C and heat stress often affects broilers towards the end of the fourth week onwards when stocking density is at its peak making it challenging to remove excess heat trapped between the birds and litter. Carefully encouraging the birds to get up and move can help release this trapped heat.

Relative humidity

Relative humidity is also a key factor to consider along with temperature, as excess moisture in the air will mean the birds’ panting (evaporative cooling) will be ineffective in reducing their body temperature. Quite often, birds succumb to heat stress during the night, and the reason for this is that the RH is higher at night despite the cooler temperature.

The Heat Index is a useful tool – if the temperature in Fahrenheit and RH% adds up to 160 or more your birds will be suffering heat stress and will be in the danger zone.

Cooling equipment

Effective temperature is the key consideration, as with the right cooling equipment a bird can feel comfortable at high ambient temperature. For instance, a good tunnel ventilation system capable of providing at least 3 meters per second of airspeed consistently across a house of fully feathered birds will provide a great chilling effect of at least 6C and remove excess heat from the poultry house via rapid air exchange.   

Misting systems or cooling pads are also good options, especially in regions with low humidity, as they cool the incoming air which will drop the house temperature, but these can be challenging in humid conditions as they will cause an increase in RH% (around 5% per 1C of cooling).

Preparation is key

Being well prepared will help prevent heat stress issues – check your houses are well insulated, check that all ventilation equipment is working before they are needed, check the weather forecast at least daily, reduce the set temperature in the evening and at night to keep the birds cooler, helping them de-stress and catch up on consumption after a hot day (this will also help them to tolerate the heat of the following day). Adding electrolytes to the water system can also help during such stressful periods.  

I hope you all have a lovely summer and remember that the team here at OPTIfarm is always available to support you and your birds through it!  

Practical Future Farming at PIX

OPTIfarm Events

This month we are heading to the Gold Coast to discuss Practical Future Farming at the Poultry Information Exchange (PIX)

This year’s event will be held at the Gold Coast Convention and Exhibition Centre from Sunday, 15 to Tuesday, 17 May 2022.


One of the most diverse ranges of solutions available to farming today and in the future is that provided by technology and data. 

We all know that our industry is facing various degrees of challenges and ever-growing risks but the demand for healthy nutritious food on our tables does not waiver. 

Practical future farming will be about reducing the risks in your business to make your farming more predictable, more manageable, and more transparent. To achieve this, expect some investment in technology along the way and the likely need for some external services and support to achieve your goals.

Poultry Tech Support Routine

Technical Corner

Latest insights and information from our Technical Director

By Nigel Strain

 Today I have provided poultry tech support to clients across four continents, without the need to leave my home here in beautiful North Wales! 

My day started by providing ventilation support to a good client based in Sydney Australia, where they were having issues with their tunnel inlets (yes – it’s lovely and warm over there currently!) It is vital that tunnel ventilation is operating correctly when it’s needed, allowing it to provide the necessary cooling effect and prevent heat stress on the birds. 


Water reduction investigation

My second task of the day was to investigate the reason for a reduction in water consumption in a broiler house for our good client in Thailand. It’s always a concern when water consumption is off-trend and a sure sign that something is amiss either in the environment or the health status of the birds.

“Optifarm is a truly global business. We are proud to provide a cost-effective and time-efficient service and care to each of our clients all over the world.”

High levels of CO2

Next request was from our good client in Johannesburg South Africa who had issues with high carbon dioxide levels in their houses. In South Africa, it’s common to use coal furnaces to heat their poultry houses. It’s important to ensure adequate ventilation; minimum ventilation is key to removing toxic air and excess moisture from the house, providing the birds with good quality air.   

Overnight temperature variations 

Here in the UK we’ve recently experienced cold overnight temperatures and windy conditions. A good client asked for advice to prevent their houses getting cold overnight. Heating capacity is so important during the winter months, and this client has the advantage of gas heaters to support their biomass system. However, minimum ventilation shouldn’t be set too high and it’s worth considering increasing set temperature slightly in the evening when you know it’s going to be a particularly cold night.  

Understanding expectations

And there was still time in the afternoon to onboard a new client via a virtual meeting! Our onboarding process is key in understanding each client’s needs and expectations, which allows us to provide a great service from day one! 

Optifarm is a truly global business. We are proud to provide a cost-effective and time-efficient service and care to each of our clients all over the world. We take great responsibility for our carbon footprint and sustainability. Innovative technology, including artificial intelligence, allows our poultry technical support team to virtually globe trot, remotely supporting clients with their technical issues without any risk to biosecurity – a great advantage given the increased threat from avian influenza, viruses, and diseases.  

A little rumination

Our new world certainly brings challenges, but there are many good opportunities too. Whilst there’s absolutely a need to be face-to-face sometimes when conducting business, we can also take advantage of remote and virtual working, and not only during a pandemic! Sitting here at my comfortable home office, I’ve embraced my new way of working and the positive changes that it brings – fewer hours wasted in traffic jams, less time away from family and friends, not having to stress about delayed flights and missed connections! Positive change is good for the soul, good for the environment, good for the pocket! 

Broiler Farm Ventilation in Damp and Cold Weather to Minimise Foot Pad Dermatitis

A Presentation that was made by David Speller (Managing Director of Applied & OPTIfarm) at the Avi Carne Forum, Madrid – 26th April, 2018


Levels of Foot Pad Dermatitis (FPD) are not only used as key welfare indicators during inspections by animal health authorities but can also lead to reduced financial returns from a flock. The resultant ulceration on the underside of the broiler foot means that moving around can become uncomfortable and as such movement to feeders and drinkers maybe impaired which can result in lower weight gains, poorer quality carcases and for processors the inability to trade lesion free feet into markets such as China. Principally FPD is caused by wet and sticky litter, although causes have been noted on our own farms due to sticky droppings.

The FPD lesion starts from an erosion of the skin caused by the litter conditions, once the surface of the skin has been eroded the lesion progresses to become an ulcer. As wells as being painful the break in the skin surface can offer an entry point for bacteria causing infections.

The aim of this paper will be to discuss the specifically the management of the ventilation to ensure the litter in the broiler house is kept dry and friable and thus the occurrence of FPD should be reduced. Other matters such as litter type, drinker management, nutrition, stocking density, genetics, light management, etc are not discussed.

Ventilation Control to Reduce FPD

Given that the major cause of FPD on farm is wet or more importantly sticky litter, keeping litter dry and friable must be a key goal. It is worth suggesting that when broilers are younger the skin cells on the feet are softer and more prone to damage and hence leading to increased resultant FPD.

What should be classed as cold damp weather is dependent on the difference between the external climate and the internal conditions of the broiler house. What we are concerned with is the difference between the internal and the external and not necessarily the specific temperature or relative humidity outside.

Basic Principles of Air & Moisture Together

  • Warm air can hold more moisture by way of water vapour than cold air
  • Warm air rises and cold air sinks
  • Simply put, warm air is light and cool air is heavy
  • Relative humidity is the amount of water vapour present given as a percentage of the total potential of that air given its temperature stated as a percentage.
  • As air temperature changes by 1-degree Celsius the ability to hold moisture changes by 5%.
  • Warm the air by 1 degree and the RH% falls by 5% as the warmer air could have held more moisture so relatively it is not as full of water any more, drop the temperature by 1 degree and the RH increase by 5% as the air is becoming saturated.
  • As air cools it is unable to hold as much water vapour and the vapour is released (Dew Point) which can settle on cool surfaces, cold windows, cold walls, cold litter.
  • Air has a mass and should be thought of like water in the way it is moved, to get air or water moving takes a force, once moving to keep it moving requires less force.
  • Like water air in small jet streams does not travel very far, but large columns of air move further but require more force, like a large water jet will go long distances but needs lots of force to propel it.

Problem with Venting in Cold Damp Weather

Firstly, lets understand how much air we need to bring into a broiler house at any one time. We all appreciate that the amount of air needed is dependent on the total amount of body weight in the shed. Lots of small birds need less air than lots of big birds. We also know that in hot weather we need more air than in cold weather.

Aside from replenishing oxygen in the broiler house a considerable amount of the air volume vented through a broiler house is done so to keep birds cool, remove moisture, remove dust and remove waste gases. The actual requirement of the bird to replenish the available oxygen required is quite low (approximately 0.5 M3/Kg/Hr).

If we remember that we have stated young birds, with softer skin on the feet, are susceptible to FPD as their skin cells can be eroded easily and a lesion can form and if we link this to the fact that younger, smaller birds need less ventilation we can start to see the problems we may encounter. We want dry friable litter to minimise the FPD, which is best achieved with lots of warm dry ventilation, but what we have is young birds with low ventilation requirements and what we are bringing into the broiler house is low volume, cool damp air as it is cold and wet outside.

Our only hope is to bring the cold damp air into the house and let it mix with the warmer air  away from the broilers in the broiler house with the aim of reaching the birds with a mixture of the airs with some fresh oxygen having allowed some of the old air to be expelled through the extraction fans or naturally aspirated vents.

However, this low volume cold damp air wants to do everything we don’t want it to do, it is cold so it wants to sink down on to the birds, it is damp and so full of moisture that wants to condense somewhere and it is in low volumes so it doesn’t want to be thrown very far.

Shed Design Assisting Cold Damp Weather Ventilation

We have many designs of broiler houses around the world with shed structure and ventilation methods designed dependant on the most common local conditions. Often the main focus is how to keep the birds cool in the summer as heat stress can kill the broilers, whilst poor venting in cooler weather, whilst impacting on performance, rarely kills the birds. In countries that are relatively cool all year we see buildings with high roofs to allow cool air to remain away from birds whilst in hooter climates the roofs are kept low to minimise the create better wind tunnels during hot weather venting. It is generally these lower ceiling sheds that create the greatest challenge to vent in cold damp weather.

So How Can We Manage to Ventilate in Cold Damp Weather and Minimise FPD

We must accept the parameters we cannot change, or at least not easily within the budget of a broiler farm, namely the external temperature and humidity.

Now consider what we can manage which is the number of inlets we can utilise, the size of the column of air we want to bring in and at what speed.

We know that cold damp air is heavy and takes a lot of force to get it moving, and we know that like water, once it is moving it takes less energy to keep it moving, therefore we might want to consider ensuring sufficient air pressure to get the air moving from no movement such as with modulating fans controls, but where we have constant fans running we may want to reduce that pressure slightly so as not to over speed the air causing excessive turbulence above the birds.

Remembering how water comes out of a hose, and that air moves like water, we know that a larger column of air moves distance better than a small fine jet of air, so in cold damp conditions aim for fewer larger air streams than lots of tiny little air streams. Some inlet manufacturers have tried to make this happen automatically.

How Does Cold Air Sinking Cause Wet Sticky Litter?

The first thing that happens when cold ventilation air sinks to the floor is that it drops down on to the litter surface leading to the litter surface cooling down. This cooler surface to the litter then allows either warmer moisture rising from within the litter or the moisture in any of the warm air above the litter to condense on the litters surface, creating moist sticky conditions.

This is especially noticeable if it occurs during dark periods when the birds are resting and the air movement in the broiler house become less turbulent without the thermal currents created by the broilers body heat warming the air in the house. In addition, the birds sit on the litter bringing the warm moist air immediately surrounding their bodies down to cold litter where the moisture can condense.

The key to successful ventilation which will reduce the occurrence of FPD is to ensure you keep the cool damp air up above the birds for sufficient time to mix with existing warm air and you must ensure the air reaches across the desired distance to replenish all areas in the broiler house.


It is possible to ventilate most facilities for cold damp weather however each location can be unique and each shed requires initial setup and monitoring. Ultimately air flow should be tested with a smoke machine as it is only then that the human eye can really appreciate where this air is going and try to predict its impact on the birds and their litter.