With record summer temperatures forecast, it’s worth reviewing how your broiler farm is set up to deal with warm weather.

There is little doubt that the UK’s climate is changing. Warmer, wetter winters and hotter summers have been recorded in recent years, with the highest ever maximum temperature recorded in Cambridge in 2019 (38.7C).

See also: How to set up and operate ventilation for broiler chicks

Last year was the 12th hottest year on record in the UK, according to the Met Office, and the 11 that rank ahead of it all occurred after 2002.

With that relatively quick spike in temperatures, it’s no surprise that some broiler units may struggle to ventilate when they need to be at maximum capacity.

Brendan Graaf, a broiler specialist with Cobb Europe, offers some tips for managing birds when the temperature rises.

Optimum ventilation

He says that the unprecedented hot weather has occasionally led to higher mortality related to heat stress and that keeping birds comfortable throughout their lives is a key way to ensure productive performance.

“There’s an optimum level where birds are taking in a good amount of energy and using very little for maintenance,” explains Mr Graaf. “This is where we want to keep them, so they have lots of surplus energy for growth and performance.”

Brendan Graaf, a broiler specialist with Cobb Europe

Birds that are too hot will soon begin to lose daily weight gains and record poorer feed conversion ratios. Stress levels will also spike, which can lead to secondary issues like a lower immune response to disease challenges.

Metabolic heat

Broilers have a high-calorie requirement – they consume about 260 calories per kg every day, compared with 55 calories per kg in humans.

Roughly 25% of that consumption is used for the bird’s essential functions, including growth, and 75% is given off as metabolic heat.

That heat is released into the air around them, which is why ambient air temperature is essential, and through the evaporation of moisture from the respiratory tract – known as latent heat loss, which is influenced by relative humidity in the shed environment.

Birds rely more on latent heat loss to control their body temperature – about a 60%/40% split – Mr Graaf says.

Signs that birds are too hot

One of the first indicators that birds are too warm is that they will spread both wings and legs.

Panting is another visible sign, and even seeing a few in a shed doing so indicates that it is likely birds are in the upper limits of their thermal comfort zone, and production is hampered.

If a bird’s body temperatures rise more than four degrees above its normal level, then it will succumb to heat stress.

An excellent place to start is with temperature set points – most systems work off this measure, though some also take relative humidity into account, Mr Graaf says.

Cobb has comprehensive guidelines in its broiler handbooks, and over the past ten years or so, those maximum recommended temperatures have been brought down.

They are based on age until 14 days, and from then on, stocking density becomes the main factor in determining temperatures.

How to manage high temperatures

In the UK, when temperatures rise higher than set points, they are primarily controlled by transitional ventilation, which draws cooler, fresh, air into units through side inlets, as opposed to tunnel ventilation more common in other countries.

The key is to get good wind speed across birds, Mr Graaf says. Some farmers worry that birds go “flat” and become less active, but “at least 25%” will continue to move and take feed and water. “It shouldn’t worry you – they will be cool, and you can give them time later in the evening to be able to catch up or compensate on feed intake they didn’t get during the day when it was hot.”

Tunnel-ventilated sheds

European poultry sheds tend to be very wide with relatively tall roofing and using tunnel ventilation in hot conditions can lead to cooler temperatures at the front of sheds and warmer climates at the back.

Birds will naturally migrate towards the cooler part of sheds, increasing stocking densities and potentially crowding feeders and drinkers. Migration fences installed in summer can help prevent this, and thereby improve bird uniformity.

Units that use side inlets

For farms without tunnel ventilation, side inlets can be trained downwards onto birds to help keep them cool.

Air will be a lot cooler close to the inlet, which can present a similar problem to uneven heating as tunnel ventilation. “You might get problems with birds migrating closer to the cool air, increasing stocking densities – the result is that birds might actually be warmer in those areas.”

Air movement can be lower close to the sidewall, as well, so it’s essential to monitor bird activity and make management decisions accordingly.

Stocking densities

The pressure that hot temperatures present is naturally highest when stocking densities approach their maximum, usually in the days leading up to thinning and before final depopulation. It is at this time that managers must be most aware of shed environments, Mr Graaf adds.

It is also worth considering whether to stock birds at a lower density in the months when the weather is hottest to minimise risk.