Minor investment
- significant influence on birds' weight

In 2019, SKOV launched a new Tunnel-Plus ventilation principle, which has some advantages in the cool/colder periods compared to a traditional tunnel system. The ventilation system must ensure that the day-old chickens can maintain a body temperature that makes them seek water and feed. A day-old chicken, which requires a surrounding temperature of 33-35 degrees Celsius at an air humidity of 50-70%, would feel very cold if the outside temperature is 24 degrees Celsius, and the air is directed straight into the zone occupied by the birds without being mixed and heated by the housing air first.

Traditional tunnel system
A traditional tunnel system takes the air in through tunnel openings (often installed with cooling pads) at the front end of the house; exhaustion of the air is conducted at the rear end of the house through gable fans. The airflow is thus created lengthwise in the house.

When it is cold outside, it may take up to ten minutes for the air to flow from the front end of the house (at tunnel opening) and to the rear end of the house (at the gable fans) in a traditional tunnel-ventilated broiler house with day-old chickens, when the grower monitors the air velocity and makes sure that it does not exceed the air velocity required by day-old chickens. The temperature and quality of the air will undergo significant changes during these 10 minutes.

Tunnel-Plus system
When the ventilation requirement is low, the air is taken in through the wall inlets in a Tunnel-Plus house. Fresh incoming air is directed towards the ceiling of the house to be mixed with the housing air before it reaches the zone occupied by the birds.

The temperature difference between the front and rear parts of the Tunnel-Plus house is reduced considerably compared to tunnel ventilation when the ventilation requirement is low.

A more stable climate results in better and more uniform growth of the birds and eliminates the need for brooding curtains and zones in a Tunnel-Plus ventilated house.

When the ventilation requirement reaches a level where the air intake via wall inlets can no longer maintain the proper temperature, the Tunnel-Plus starts ventilating according to the traditional tunnel principle.

A case study from Indonesia
In large parts of Southeast Asia, the broiler houses are made with traditional tunnel ventilation. During 2018-2019, SKOV carried out a real-life test in Indonesia to compare a traditional tunnel ventilation system with a Tunnel-Plus ventilation system under the same conditions.

We installed two broiler houses with traditional tunnel ventilation and two houses with the new Tunnel-Plus ventilation system on the same farm.

We measured the temperature in the front and rear zones and looked at the temperature difference between the two zones.

In the house ventilated by traditional tunnel ventilation, there was a temperature difference from rear to front of more than four degrees Celsius during the first days after production start. In the Tunnel-Plus ventilated house, the temperature difference was only between one and two degrees Celsius.

Two degrees do not sound of much, but the consequences are evident at the end of the batch. The great temperature difference in the house with traditional tunnel ventilation leads to a significant weight difference of 50-70g a few days before the birds are slaughtered.

In the house ventilated with the Tunnel-Plus system, the difference is only 10-35g during the respective time interval.

The result of this test shows that an investment in Tunnel-Plus improved the uniformity of the batch and reduced the weight difference of the birds at slaughter day from 50-70g to 10-35g. The improved uniformity ensures that the birds in the rear and front zones of the house have the same optimum FCR as the birds in the center of house. In general, the birds are ready for slaughtering ½ - 1 day before, and the cost of sending a non-uniform batch of birds to the slaughterhouse is eliminated.

The two graphs below show how many degrees Celsius the temperature differs between the front and the rear of the two houses, along with the weight difference of the birds.

Traditional Tunnel House
The big temperature difference between front and rear of the house from 27-12-2018 to 04-01-2019 can explain the big weight difference of the birds in the end.