Creating the optimal housed environment for finishing pigs

The levels of ammonia (NH 3 ) and carbon dioxide (CO 2 ) in straw-based finishing units can impact pig health, having a knock-on effect on growth rates from weaning through to finishing.

Galebreaker is currently investigating how Variable Ventilation Solution (VVS) side curtain systems can be adapted to enable the reduction of NH 3 and CO 2 from pig units when they exceed a certain level that can be detrimental to pig health.

The effects of ammonia and carbon dioxide on pigs

When present in higher concentrations, CO 2 affects pigs by causing them to become lethargic. This can reduce feed intake and will impact growth rates if levels of CO 2 remain high over a sustained period.

High levels of NH 3 in the environment can damage the linings in a pig’s respiratory tract which secrete mucus, causing the self-cleaning capacity of the lungs to be reduced. This reduces the bacterial clearance from the lungs, making pigs more susceptible to respiratory disease.

NH 3 can also cause irritation to the eyes, nose and throat which can stress the pigs, causing behaviours like tail biting. It’s also a harmful and unpleasant gas for staff working on pig rearing unites to be exposed to.

Managing the environment inside finishing pig housing

VVS side curtain systems are frequently used to create the optimal environment for pigs – no matter the time of year, weather conditions or the age and size of housed pigs.

As pigs are particularly sensitive to temperature, a VVS system enables farmers to set the desired temperature according to the age of pigs housed at any time. For example, if young, recently weaned pigs are housed, they will thrive best at temperatures between 18 and 20°C.

The system can be programmed to open the curtains to increase airflow when the temperature exceeds the optimal level, and to close again if it drops too low. Other benefits of VVS systems include:

• The use of wind speed and direction and rain sensors to detect and react to changes in the external environment, enabling continuous optimisation of the housed environment for finishing pigs
• Flexibility to changing weather conditions throughout the year
• Easier to clean than other housing options like cladding, enabling improved biosecurity

Adapting VVS systems to include ammonia and carbon dioxide
levels

With vets recommending that NH 3 in pig housing should not exceed 20 parts per million (ppm), and CO 2 having an impact on feed intake, being able to adjust systems to respond to an accumulation of ammonia or CO 2 above a set threshold is hugely beneficial.

Galebreaker is currently looking to improve the VVS side curtain system by conducting experiments to understand the build-up of NH 3 and CO 2 when the curtains are closed and how long it takes for the gases to clear once the curtains are opened.

Experiment findings

In the first experiment – which took place on a still day with little breeze, in a shed which was at 70% capacity with pigs close to slaughter – the curtains were completely closed with 0% ventilation at approximately 6:20am.

After two hours at 0% ventilation, the NH 3 concentration rose from 1ppm to 58.51ppm and the CO 2 concentration rose from 1,057ppm to 3,775ppm. The team conducting the experiment noticed the environment in the shed was warm and humid with a noxious smell.

After opening the curtains, both the NH 3 and CO 2 concentrations dropped back down to normal levels within 30 minutes.

The team intends to conduct further experiments to understand the point at which increased NH 3 and CO 2 levels become unpleasant or detrimental to pigs and staff, with the view to adapt the VVS control system to be able to override the temperature control when the building needs to be refreshed with clean air.

To see the latest updates from the Galebreaker agricultural team visit our homepage, or for tailored advice on ventilation in pig finishing systems get in touch with the team.