Air quality: The key is resolving ammonia and moisture issues

The level of oxygen in a poultry barn isn’t a problem, according to Dr. Mike Czarick.

The level of oxygen in a poultry barn isn’t a problem, according to Dr. Mike Czarick.

Speaking on Broiler House Air Quality at the Western Poultry Disease Conference in Vancouverhe said although brooders burn oxygen, low ventilation rates provide adequate oxygen for the young chick – even with the extra moisture that the brooders produce.

Even with older birds the oxygen (O2) needs are still very small. “So, if it’s not the oxygen, what is it?” Czarick asked. “Is CO2 (carbon dioxide) the far more likely culprit?”

He displayed a graph showing how oxygen requirements slowly, but steadily, increase during the life of a flock, with a second line rising far more steeply, representing fast increasing CO2 output as the birds age. “In fact, ventilation rates to resolve CO2 problems are 30 to 40 times greater than those required to supply the oxygen needs of the flock,” Czarick said. However, he went on to stress that, “the major reason for specific ventilation rates is to limit ammonia buildup and to control moisture levels.”

He said that if ammonia (NH3) levels reach 75 ppm the flock weight is negatively affected, uniformity suffers and meat yield is down. In these cases, post-mortem inspection shows that the cilia in the bronchial tubes are damaged. In contrast, up to 25 parts per million of NH3 is acceptable. However, although increased ventilation will start to reduce ammonia levels, more and more effort is required to knock it down even further. Adding heat will help, as will litter treatments, which generally require over seven lbs. of product to neutralize one lb. of NH3 gas.

Czarick then displayed heat camera images showing how the borders of the house cool and drafts start to appear as air exhaust increases.

“In fact there is no easy answer to NH3 control on built-up litter. Ammonia production in a 1000-sq. ft. area can vary from 2.8 lbs. per day to 10 times that level.” He added, “Ammonia generation is generally higher at the end of the growing cycle, then after we ship the flock, we turn the heat off, break up any surface cake and air out the house.

Ammonia levels seem to be under control, but then we heat up the litter again as the new chicks arrive and there is a new surge of ammonia production.”

He said that there is a need to manage the environment between the flocks. The surface cake must be removed, the litter should be composted, water lines repaired and an attempt made to dry the litter. He pointed out that this last measure would reduce condensation and therefore rusting and deterioration of barn equipment. But he cautioned that too dry litter has its own problem of dust and consequent respiratory problems.
Czarick reminded veterinarians that for every one lb. of feed consumed, the birds drink – and expel – two lbs. of water. “So a water meter is the best indicator of the ventilation rate required. It’s calculable. Minimum ventilation rate charts are, in fact, moisture control charts – although this is never mentioned.”

Air Flow Management
Ensuring correct air replacement levels is but the first step. The second step, Czarick stressed, is that the incoming air must be mixed with barn air up near the ceiling to provide air quality with a comfortable house temperature and air speed at bird level.

To achieve this, Czarick recommended placing air intakes high on the wall and adjust them to keep air speed up, ‘jetting’ it close to the ceiling. To achieve proper air mixing, the ceiling should be free of obstruction to the incoming air. “A single pipe on the ceiling close to the inlet will stop the cool incoming air dead, which will then drop directly down on the birds as a draft.”

Czarick stressed that to keep ventilation under control the house must be ‘closed,’ except for the inlets, “and this must be checked with a smoke dispenser or with thermal imagery, which will show chilled chicks and wet, caked litter.”

Another step in airflow management is to avoid stratification of the air in the barn. “It’s possible to get a 20ºF differential in temperature in eight feet of height. So mix it up!”
He recommended the use of circulation fans to keep the air speed up at ceiling level, but located so that air speed at floor level remains low. His final comment was to stress that heat leaking through side wall curtains takes no moisture with it, therefore making adequate moisture and ammonia control that much more difficult.