Ammonia concentration within the sheds is one of the most serious performance and environmental factors affecting meat chicken production (Miles et al., 2004; Ritz et al., 2017). When chickens consume protein, they produce uric acid, which is converted to ammonia gas under favourable conditions. Factors in litter that increase ammonia production include pH, temperature, moisture content, bedding type, chicken age, manure age, relative humidity and ventilation rate. While ammonia is an issue in meat chicken production, it is a symptom of other factors, particularly moisture levels.
At high concentrations, ammonia irritates the mucous membranes of chickens’ respiratory tracts and the conjunctivae and corneas of the eyes. Damage to the mucous membranes of the respiratory system increases the susceptibility of meat chickens to bacterial respiratory infections, especially E. coli infection. The ammonia level, combined with the exposure period, can also negatively impact liveability, weight gain, feed conversion rate, condemnation rate at processing and their immune systems (Aziz & Barnes, 2010).
Ammonia is also a severe respiratory tract irritant in humans and has caused severe damage and death when found in doses well above typical workplace standards (EnviroMed Detection Services, 2020). It is listed as an airborne contaminant under Australian WH&S standards. The eight-hour time weighted average (TWA) exposure standard for ammonia under this framework is 25ppm. The eight-hour TWA means the maximum average airborne concentration calculated over an eight-hour working day, for a five-day working week. Under this standard, the short-term exposure limit (STEL) must not exceed 35ppm. The STEL is the maximum airborne concentration measured over 15 minutes (Safe Work Australia, 2013).
It is possible that ammonia concentrations within meat chicken sheds can cause health issues for chickens and workers where levels exceed 25ppm. Australian animal welfare standards require ammonia levels to be below 20ppm, with some farming schemes requiring the concentration to be lower than this. Naseem and King (2018) suggested the ideal concentration in sheds should be below 10ppm.
Australian research (Walkden-Brown et al. 2010) has shown that litter reuse causes higher ammonia concentrations, although in this research the concentrations were well below the threshold of 20ppm where meat chicken performance and health may be compromised. The ammonia concentration in multi-batch litter is likely to be higher than in single-batch litter, and care should be taken to manage this risk to chicken health, particularly during brooding in winter. However, this is unlikely to pose a major risk in Australia, where only partial reuse systems (fresh bedding material for brooding) are used, as opposed to full reuse systems not practiced here.
In-shed ammonia concentrations in single and multi-batch use systems can be managed if they become a concern. Strategies include increasing ventilation and the use of litter additives (see Litter additives for a description of various litter additives and the Pre-treatment guide on best management of their use). At present, the use of litter additives in Australia, in either single or multi-batch systems, is minimal (Wiedemann, 2015b).
