How poultry unit manages heat stress with misting systems

High-pressure water misting systems are playing a key role in preventing heat stress and performance dips in hot weather at one Derbyshire broiler business.

The Adsetts family installed their first misting system in 1999 and it was so successful in keeping birds cool on hot days that they now have 16 across their three sites.

See also: 3 poultry diseases to look out for in 2022

Effect of heat stress 

All types of poultry can be affected by heat stress but the birds most at risk are broilers that are nearing the end of their crop cycle.

Birds are heat stressed if they have difficulty achieving a balance between body heat production and body heat loss – this can occur at all ages and in all types of poultry.

Panting is a normal response to heat and is not initially considered a welfare problem but as temperatures increase, the rate of panting increases, affecting production performance.

How does the system work?

When the outside air temperature is forecast to be higher than 28C, the misters operate for the entire day.

On other days when the heat is less intense they are used strategically for a few hours when the temperature is set to peak.

“We are proactive rather than reactive,” says George Adsetts, who farms with his father, David, and sister and brother-in-law, Elizabeth and Robert Saxton.

The main aim is to stop the shed temperature building and to prevent heat stress.

“We operate the misters in good time on a hot day, they come on at 9am or 10am, before the temperature starts to skyrocket.”

Starting the system early in the day cools the sheds down before the birds start to pant.

As soon as the misters are activated, the house temperature can drop by 7C. “The temperature drop is pretty instantaneous,” Mr Adsetts reports.

The system is switched on once birds reach 21 days old. It runs off a sensor, which can detect rising temperatures from the start of the day.

Misting systems work by intermittently spraying a small amount of water into the incoming air stream, not directly onto the birds.

The cool, moist air helps to remove heat from the atmosphere as it is drawn through the shed by the ventilation system, creating a wind-chill effect.

The family have always opted for high-pressure systems – in their case a Lubing supplied by Ripon-based Dalton Engineering – as low-pressure types can cause problems with lingering moisture.

“There are many systems on the market and years ago it could have been as simple as a hosepipe and sprinkler. But these systems can use a lot of water and create a lot of damp,” Mr Adsetts explains.

Humidity

Concerns about raising humidity levels in the birds’ environment by combining water with heat is the main reason why broiler producers are sometimes put off the idea of misters.

“Misting systems are quite divisive, they are a bit of a ‘Marmite’ in the industry,” says Mr Adsetts.

Some broiler producers believe they raise humidity in the house and actually increase mortality through respiratory disorders and disease.

But high-pressure systems create a finer mist. While the system does add to the humidity in the shed temporarily, moisture is rapidly removed by the ventilation system before it descends on to the birds.

If the misting is turned on when the temperature starts to rise, humidity never needs to be out of control, Mr Adsetts says.

Ventilation 

At the Adsetts’ farm all units are well ventilated and so humidity is quickly addressed  and has never been a problem.

He reckons that even with advancements in modern ventilation systems the value of misting systems must not be underestimated.

“Ventilation systems alone move a considerable amount of air and this creates a significant wind-chill effect but what this means is that you are running a very hot shed with a high wind speed,” Mr Adsetts points out.

While this may prevent mortalities, he reckons birds will be less inclined to eat in that environment, which will then have an impact on performance.

Mr Adsetts feels they get a big performance benefit even on the days that they are not getting the very high temperatures.

“Those are the days when we might get a temperature spike later in the day, which could create a small production loss if we had no misting system,” Mr Adsetts says.

The system will run for just two or three hours in that spike period, to limit any effect of the rising temperature.

The sprinklers make birds get up and move around more, releasing body heat, and encourage visits to the feeders.

“They continue to eat and drink as normal,” says Mr Adsetts.

What does the system cost?

At about £8,000 to install a Lubing system in a 40,000-bird shed, Mr Adsetts says the set up costs are relatively high but maintenance is minimal.

“It is fairly low-value maintenance. We just need to replace some of the nozzles from time to time.

“The system is basically a pump and pipework, but a very good design and very simple to operate once it is in.”

Before the pandemic, the business had produced 4kg cockerels for the food service industry but when that market collapsed during the lockdowns, it shifted production to smaller birds.

It was through their experience of growing a bigger bird that the Adsetts recognised the benefits of misters.

“The bigger birds were more susceptible to heat stress due to their overall size and ability to lose heat, and the extra stress that put on their heart,” says Mr Adsetts.

How are the risks managed?

The combination of water sitting in the pipes at high temperatures, early in the crop, can make misting systems a breeding ground for bacteria.

To prevent this, a very weak disinfectant solution is run through the system once every crop.

A complex filter system also reduces the risk of infection by preventing dust and dirt particles from getting into the system.

What are the performance improvements?

A key performance indicator is mortality rate. This averages 3-4% year-round across the Adsetts’ units.

There are no summer mortalities resulting from heat stress, which Mr Adsetts puts down to misting. “It is, therefore, good for welfare and profitability,” he says.

Growth rates and feed conversion efficiency – which can vary from crop to crop – are not compromised on hot days either, he adds.