Ammonia (NH3) is an invisible, water-soluble alkaline gas, which is hazardous to the environment. If contamination of soil or water occurs, it may cause environmental problems such as acidification and eutrophication, which can harm sensitive vegetation systems, disrupt biodiversity and reduce water quality. In the European Union (EU), the agricultural sector is responsible for the vast majority (93.3%) of total ammonia emissions. Livestock manure management (collecting, storing and spreading on land) accounts for almost three fifths of agricultural ammonia emissions, while agricultural soil emissions account for the rest (Figure 1).
Ammonia emissions in poultry houses
Ammonia in a poultry house comes from the birds themselves. Unused nitrogen is excreted as uric acid (80%), ammonia (10%), and urea (5%). When ammonia gas is exposed to moisture, it reacts and forms a basic, corrosive solution called ammonium. This aqueous ammonium solution causes harm to birds. The ammonium corrodes the lining of chickens’ respiratory tract and paralyses or even destroys the cilia of the epithelial cells. In such conditions, the mucus on the mucosal surface of the trachea cannot be cleared by the cilia and thus bacteria become trapped. When the bacteria reach the lungs or the air sacs, they cause infections.
Considering both human and animal health, guideline exposure levels for ammonia is set to 20-25ppm in many countries. However, in practice, the concentration of ammonia in some broiler houses may easily exceed 30-70 ppm, particularly in wintertime. The EU directive (Council Directive 2007/43/EC) states that the NH3 concentration should not exceed 20 ppm over any eight-hour period or 35 ppm over any ten-minute period during the poultry production cycle.
Effects of ammonia on birds’ health and performance
A high concentration of ammonia in the poultry house has adverse effects on the health and performance of birds. However, it is not easy to measure the magnitude of such adverse effects.
Birds are not usually exposed to a very high concentration of ammonia for long periods, unless there is poor ventilation, or birds are fed a nutritionally unbalanced diet. Recent research has revealed that many molecular changes can take place when birds are challenged with a high concentration of ammonia, even for short periods. The presence of excessively high levels of ammonia in the air, for any length of time, will cause discomfort for the birds. Ammonia is a strong oxidative stressor that can cause inflammation. Trials have shown that high concentrations of ammonia can alter the normal organ function of animals, impair energy metabolism, induce cell apoptosis, and cause mitochondrial damage in the mucosa of the gastrointestinal tract.
Poor growth rate and performance of birds growing in high atmospheric ammonia concentrations is strongly related to the influence of ammonia on birds’ immunity and their intestinal histomorphology. Exposure to high ammonia concentrations negatively affects the development of the birds’ immune system as well as intestinal villi and mucosal proteome.
Ammonia management in poultry production
The goal for most producers is either to avoid high concentrations of ammonia in the first place, or to control induced inflammations and minimize the impacts on bird health and performance. Here are five ways to reduce ammonia levels in poultry houses:
- Ration composition and diet management, provision of a balanced, complete diet is of the highest importance. Problems occurring due to high-performance genetics, feed formulation and medication can lead to production of wet manure, causing increased ammonia and odor release alongside reduced broiler performance and feed efficiency.
- Optimize the poultry stocking density to help limit excessive moisture in the poultry house, so reducing anaerobic processes.
- Adjust the ventilation rate – if ammonia levels increase, more ventilation is needed. However, this should only be in accordance with the climate and temperature of the poultry house.
- Temperature adjustments should be made relating to house climate and welfare.
- Improve nutrient digestibility. This could also be achieved by supplementing diets with additives.
Of this list, dietary management is the most important preventative measure. The total amount of nitrogen within the birds’ feces can be considerably reduced by formulating diets based on the birds’ amino acid requirement instead of on total crude protein. As the percentage of crude protein in the diet is lowered and replaced with conventional sources of protein (e.g. soybean meal, sunflower meal) with synthetic amino acids, nutrient retention is maximized. Reducing dietary protein by 3-5% may cause a reduction of 60% or more in total nitrogen excretion from broilers and laying hens.
A well-balanced diet contains highly digestible ingredients and functional feed additives that can improve the digestibility of nutrients in the small intestine of birds. Inflammation caused by stress may dramatically decrease the ability of the birds to digest and absorb nutrients including proteins.
An inflamed and unhealthy intestine is not capable of absorbing digested feed, even if the digestion has been enhanced by exogenous enzymes. Keeping the gastrointestinal tract healthy and functional during the whole growing period is key to reducing the excretion of undigested and unabsorbed feed in the feces which will in turn reduce the ammonia volatilization within the poultry house (Figure 2).
Phytogenic Feed Additives (PFAs)
Phytogenic feed additives are capable of increasing the digestibility of nutrients within the gastrointestinal tract and reducing gut inflammation caused by stressors. These two important effects of PFAs may considerably increase the gut integrity of the birds. Phytogenic feed additives also modulate gut microbiota, minimizing the negative effect of harmful bacteria on the gut. Less undigested and unabsorbed nutrients will be passed to the feces from a healthy gut, which means less nitrogen excretion from the birds to the environment. Less nitrogen excretion reduces ammonia volatilization within the chicken house to a great extent.
In a recent trial, Digestarom® Poultry, the PFA offered by BIOMIN, was added to the diet of one group of birds while the control group had no PFA added. Over the duration of the trial, the ammonia concentration in the Digestarom® Poultry house was 12.12% lower when compared to the control group. The airflow rate was 14.19% lower and the ammonia emissions were significantly reduced (11.71% lower) in the treated group compared to the control group. Total nitrogen in the litter of the treated group was 33.93 kg/t, 8.01% lower than 36.89 kg/t as measured in the control group. At the same time, the performance of the birds in the Digestarom® Poultry group increased both in terms of daily live weight gain and feed conversion ratio. The improvements were measured as 1.6 g/d and 4 FCR points - as shown in Figures 3 and 4 respectively.