Heat stress can have a huge impact on bird health, welfare and performance and with warmer weather on the horizon, now is the time to start preparing your site to reduce the effects, and stock up on the products you might need.
What is heat stress?
Heat stress is due to a rise in the bird’s body temperature; their normal temperature (depending on the age of the bird) is 39.5-41 degrees. If the bird’s temperature exceeds 41 degrees, it can lead to massive cell damage and systemic inflammation, leading to shock and death.
What implications does heat stress have on the birds?
If the heat stress is mild, then the impact can be poorer growth for broilers and lower egg production for layers (together with egg shell changes). In extreme circumstances increased mortality can ensue.
Aside from the above major issues that heat stress can cause, there are other possible implications particularly for broilers where they don’t want to feed by day, so when it cools down at night, they scratch others leading to cellulitis rejects at slaughter. The increased pressure on their cardiovascular systems can increase the levels of ascites rejects too. Alongside this the birds panting to cool down can affect their blood pH leading to possible leg health issues.
What are the signs of heat stress?
The birds will do several things to try and cool themselves down, the main ones being moving away from other birds, moving to a cooler area and holding their wings away from their body. If these behaviours aren’t enough to cool the bird, they will start panting. This can cool birds through evaporative cooling, and the physical process called latent heat evaporation. The lower the humidity in the air surrounding the birds, the more effective the evaporative cooling will be.
The importance of understanding wind speed, air temperature and humidity
The temperature that the birds feel will be a combination of the air temperature, the humidity and the wind speed. The air temperature can remain the same over a few days, but if the humidity changes, the birds will feel different temperatures.
How does humidity affect heat stress?
As a main rule, for every 10% the humidity increases, the temperature the bird feels will rise by 2 degrees. Think of 30 degrees in the desert vs 30 degrees jungle. Most heat stress related fatalities will occur in the evening due to the humidity being higher.
Use a heat index calculator to determine the temperature the bird is feeling. For example, a temperature of 34 degrees and 40% humidity gives a heat index temperature of 35 degrees, but if the humidity changes to 65%, the heat index temperature changes to 44 degrees, meaning the birds will die.
The heat index is calculated as the temperature in Fahrenheit + humidity. If it is over 160 then the birds can suffer from heat stress. The reason for this is with high humidity it reduces the evaporation of water from the birds’ airways making it harder for birds to cool themselves. Hence they feel warmer with high humidity.
How do I control the air temperature of the shed?
Historically traditional sheds have been controlled through windspeed. However, this isn’t always going to work. If the temperature is approaching the bird’s temperature of 40-42 degrees no matter how fast the air moves over the birds, it can’t cool them.
What are the other ways of controlling shed temperatures?
Misting systems can be used to cool sheds but care is needed if the outside humidity is high as this can exacerbate heat stress. Evaporative cooling pads can be used to cool air entering the sheds.
I’ve got a misting system – what should I be looking out for?
In recent years when there’s been spikes in temperature, fans alone haven’t always been enough to cool the air. Misting systems – commonly used in areas of the world with consistently high temperatures – is one of the alternatives. However, they need to be set correctly and monitored, to be effective.
Misting systems rely on the evaporation of water to cool the incoming air. It’s important to keep an eye on the relative humidity of the incoming air as this will determine to what degree the air can be cooled – the higher the humidity, the less effective the cooling. This is one of the limitations of these systems.
Misters must also produce fine water droplets. Check that these droplets evaporate before they get to the chicken or ground. If not, this will lead to wetting, will increase the humidity around the chicken, and make them feel worse.
How to prevent heat stress
Prep your site
- Ensure the environment is dry, remove wet bedding and fix leaky drinkers
- Get the temperature of the shed as low as possible
- Identify and remove any sources of humidity such as puddles around the house aprons
- Clean the water lines
Keep an eye on the weather forecast – This may be stating the obvious, but if you know when the hotter temperatures are coming, you can start taking measures to reduce the temperatures in the sheds before it gets too warm. The ‘perfect storm’ of heat stress is when there’s hot weather, followed by rain, followed by more hot weather as this will increase humidity.
General advice and guidance
The below is some general guidance and recommended products to support your birds before, during and after a period of hot weather. However, it’s important to have a plan that’s tailored to your site and situation – get in touch with our team on 01392 872932 or email us at info@stdavids-poultryteam.co.uk for guidance on a more site specific approach.
| A couple of days before high temperatures | A day before & during the heat wave | After the heat wave (around 8-12 hours after) | A day after the heat wave |
| Aqua-clean through the drinker lines | Heat Stress Plus | Turn off Heat Stress PlusFlush the drinker lines | Elanbiotic for a few days afterAqua-clean through the drinker lines |
Another supportive product that can help the birds during hot weather is Solulyte Plus. It contains a blend of electrolytes (minerals/body salts) and flavours which optimise water consumption and supply essential body salts.
Watch the birds for a change in behaviour – If the birds are getting too hot, their behaviour will start to change, such as holding their wings away from their body and panting.
Ensure all fans are working – Test out the fans in your sheds before the hot weather arrives, to ensure they are able to work to full capacity.
Turn your heaters off – Again, it may be stating the obvious, but ensure your heaters are turned off so they aren’t contributing to the heat
Have an up-to-date heat stress plan – Have a plan in place for the steps to take to reduce heat stress on your flock. Speak to your local vet if you need assistance getting a plan in place.
What to do during a heat wave?
- Lower the drinkers and increase water pressure slightly
- Provide supplements if the birds are showing signs of heat stress
- Chill the drinking water
- Increase the ventilation until it’s on maximum
What to do after heat stress?
- Encourage the birds to eat and drink. They would have used a lot of energy by panting.
- Look out for secondary symptoms a few days after. Birds are prone to digestive problems three to four days after. You can support the birds with nutraceutical products such as Integrity, Herbavit and Elanbiotic.
- Consider using Energy Plus which provides metabolised energy, liver support and includes specific plant extracts which aid healthy digestion.
It’s important to have a plan that’s tailored to your circumstances. For advice and guidance give us a call on 01392 872932 or email us at info@stdavids-poultryteam.co.uk