Best practice litter management manual for Australian meat chicken farms

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Shed heating and cooling to control litter moisture guide

Why important: Wet litter can have adverse effects on chicken performance, welfare and health, worker health, food safety, and the environment. Effective ventilation, heating and relative humidity control are necessary to reduce the incidence of wet litter.
Outcome: The internal environment in sheds is optimised by maintaining and managing the heating and ventilation systems. This will minimise odour and ammonia production from the litter.
Performance measure: Supply sufficient ventilation to remove excess moisture from sheds, optimise meat chicken thermal comfort, remove ammonia from sheds to minimise chicken welfare issues, and reduce WH&S risks.
Best management actions:

Shed and equipment maintenance
  • - Inspect ventilation and cooling systems daily to ensure they are working effectively, and complete maintenance when problems arise. This includes inspecting cooling pad collection trays, foggers and associated pipework.
  • - For mechanically ventilated sheds, ensure that they are airtight, and as much air as possible enters through ventilation openings. The most common leak points are around door seals, through broken mini vents and through unsealed fan shutters.
  • - When sidewall curtains are used, ensure they can be tightly closed.
  • - Repair any holes found in ceiling insulation.
  • - Between growth cycles, check fan efficiency rates, heating and ventilation system, extraction and inlet openings. This includes checking the rated fan capacity (i.e. revolution per minute) and that shutters work.
  • - Provide back-up generators that can fully ventilate sheds and associated equipment. These require operation at least weekly on full load to ensure they work effectively.

Ventilation operation
  • - Operate fans and the ventilation system in cold weather in a way that prevents moist incoming air from condensing on the floor next to the walls. Shed design will determine the best way to do this, but options include using stirring fans, deflectors, baffles and other devices to improve air mixing. Other options include adjusting mini-vent angles, ventilation opening widths and ventilation velocity.
  • - Increase ventilation rates if ammonia and wet litter become problems. This is done by systematically increasing ventilation time or fan speed (for variable-speed fans) until sufficient ammonia and moisture extraction is achieved.
  • - When increased ventilation is used to remove ammonia and moisture from sheds, temperature and humidity must be maintained (possibly requiring the use of heaters) to levels appropriate to the age of the chickens.
  • In winter, provide heating to sheds to improve moisture removal, as warmer air holds more water. This may also require more ventilation to ensure meat chicken thermal comfort is maintained.
  • - Ensure incoming air has a low relative humidity (<60%) as much as possible to enable moisture to transfer from the litter surface to the ventilated air. Only rely on the evaporative cooling system when required to assist with this.
  • - Incoming air with higher relative humidity (>60%) should be managed via stirring fans, deflectors, baffles and other devices to improve air circulation, minimise hotspots and remove excess moisture.
  • - If in-shed ammonia concentrations are an issue and cannot be managed by ventilation alone, consider the use of litter additives such as acidifying agents and/or microbes that can bind nitrogen and reduce volatilisation rates. The benefits from these will be greater where multi-use litter practices are adopted.

Monitoring and recordkeeping
  • - Maintain shed ammonia concentrations below 20ppm.
  • - To meet minimum standards under some farming schemes, lower shed ammonia concentrations may be required, and these will likely vary with bird age.
  • - To ensure adequate air mixing in tunnel ventilated sheds, static pressure should be at least 30Pa to ensure airspeed entering through mini-vents is between 3–6m/s.
  • - Take ammonia readings in every shed at least twice per week upon first entering, or at least twice per week within one hour after litter maintenance activities have ceased.
  • - Keep records of ammonia readings, including when and where taken and equipment used.
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