Impact of chronic ammonia exposure in pigs

Impact of chronic ammonia exposure in pigs

In recent decades, the intensification of pig production has led to high concentrations of ammonia emissions in commercial pig farms around the world. Ammonia is one of the main environmental pollutants produced by natural and anthropogenic sources, with detrimental impacts on public health and on the health, welfare and productive performance of pigs. In addition, ammonia plays an important role in the development of atmospheric particles, the degradation of visibility and the atmospheric deposition of nitrogen in sensitive ecosystems. This, in turn, affects the environment and leads to climate change.

Therefore, it is important to have a clear understanding of ammonia sources, impacts, and approaches to solving this challenge. This article integrates the available knowledge on ammonia production through commercial pig farms, describes the health implications of ammonia emissions, and explains effective control strategies to address this problem.

What is ammonia?

Ammonia is an important component of total reactive nitrogen. In addition, it is an alkaline gas that is soluble in the atmosphere and can be easily converted into fine-particle ammonia aerosols. Ammonia is a colorless gas that is lighter than air. It has a strong, pungent odor that people can smell at 5-18ppm. The decomposition and volatilization of urea produces ammonia. It is soluble in water and converts to ammonium ion. 99% remains in liquid form at low pH (<7, condiciones ácidas). A pH alto (>7, basic conditions) part of the ammonia turns into gaseous ammonia and escapes when exposed to the open air. When the pH is 9.25, 50% of the ammonia is in the gaseous state and the other 50% is in the liquid form.

What are the sources of ammonia?

Ammonia originates from both natural and anthropogenic sources. Anthropogenic sources, which are the largest source of ammonia emission, include agricultural activity, animal husbandry, and waste. They also include the application of ammonia-based fertilizers, the volatilization of chemical fertilizers, the burning of biomass, catalytic converters in gasoline cars, landfills, sewage works, composting of organic materials, combustion of fossil fuels, and industrial processes.

Natural sources of ammonia emission include wild mammals and birds, volatilization of soils and oceans, and microorganisms that break down organic matter. Ammonia from anthropogenic sources has become a public concern due to its harmful effects on public health and the environment, as well as on animal health, welfare and production performance.

Ammonia emissions from the pig industry

Pigs consume protein and other forms of nitrogen in feed to produce meat. However, the conversion of feed to meat is inefficient. Pigs excrete between 50 and 80% of the nitrogen in the feed in faeces and urine. Biological and chemical breakdown of manure protein, uric acid and urea generate ammonia. This means that pig barns, manure storage, and land application of manure are the main sources of emissions.

Among the livestock industry sectors, pig production contributes about 12% of total ammonia emissions to the atmosphere. Manure moisture content, temperature, nitrogen content, aeration conditions, manure pH value, and chemical and microbiological activities affect ammonia formation and emission.

What are the harmful impacts of ammonia on pigs?

In 2022, a study conducted by a team of researchers led by Wenhao Qin in Huazhong Agricultural University in Wuhan, China, found that in piglets, exposure to 50 ppm ammonia causes obvious lung injury, including interstitial thickening, inflammatory cell infiltration, and focal hemorrhage. Furthermore, ammonia exposure led to increased malondialdehyde content combined with decreased expression of antioxidase mRNA and inflammatory regulators. It also induced oxidative stress and decreased anti-inflammatory response in lung tissues. In addition, there were accumulations of succinic acid, linoleic acid, and phosphorylethanolamine and consumption of glucose, quinolinic acid, and aspartic acid in the ammonia exposure groups. This indicated that the energy supply from aerobic glucose oxidation is suppressed and glycolysis and lipolysis in lung tissues, induced by chronic ammonia exposure, are activated.

In 2020, also at Huazhong Agricultural University, Xiaotong Wang and colleagues reported that short-term exposure to 80 ppm ammonia induces nasal mucosal hyperplasia. It also induces ciliary dysfunction and epithelial-mesenchymal transformation and lung injury. Furthermore, prolonged exposure to ammonia inhibits the Krebs cycle and activates glycolysis in the lungs of piglets. Even in low concentrations, ammonia is considered a toxic gas for humans and animals. Due to ammonia’s high solubility in water, it can irritate and corrode the respiratory tract upon inhalation. In addition, ammonia affects the intestines, spleen, liver, kidneys, heart and brain through mucous membranes and blood circulation.

Harmful bacteria and pathological changes.

In 2019, a study by Tongxin Wang and colleagues from Huazhong Agricultural University showed that exposure to ammonia with a concentration above 20 ppm can decrease the abundance of nasal microbiota and increase the colonization of harmful bacteria in the nasal cavity of growing pigs. In addition, the imbalance of the nasal microbiota causes disorders of the immune function of the respiratory mucosa and respiratory diseases. Furthermore, chronic exposure to high concentrations of ammonia alters the diversity of the gut microbiota and induces an inflammatory response in finishing pigs.

In 2021, a study by Chunli Xia and colleagues from Northeast Agricultural University in Harbin, China mentioned varying degrees of pathological changes in the liver, kidneys, hypothalamus, jejunum, lungs, spleen, heart and the trachea of ​​finishing pigs exposed to ammonia. In particular, the extent of damage to the liver, kidneys, jejunum, lungs, hypothalamus, and trachea is more severe than to the heart and spleen.

In 2011, a study by Andi Mushawwir and colleagues, at the time attached to the Research Institute of Agriculture and Life Sciences in South Korea, concluded that ammonia exposure reduces the function of olfactory receptors, decreases activities of the Calcium-controlled chloride channel, reduces electricity sends signals to the brain and affects blood metabolism in sows.

How can farmers tackle the problem?

Surface area, surface airflow, air temperature, relative humidity, and air ammonia concentration difference in manure affect the emission of ammonia into the air. Therefore, ammonia emissions can be reduced by separating urine and faeces, separating manure from oxygen, little manure disturbance, and low speed. air flow above the manure. Also, reducing the ammonia concentration in the suspension by dilution, lowering the suspension temperature, lowering the emission surface, and lowering the pH will decrease the ammonia emission. Dietary manipulation to decrease ammonia emission includes reducing dietary crude protein and supplementing crystalline amino acids, adding fiber sources such as small amounts of soybean hulls or dried sugar beet pulp, and supplementing calcium salts.

Final remarks

Ammonia is a major air pollutant causing environmental and public health concerns, as well as the health and welfare of pigs. Although adverse effects of ammonia exposure occur in pigs of all ages, the molecular mechanisms remain unclear and are the subject of further investigation. Understanding ammonia emission and dispersion is critical to reducing ammonia emission from swine production facilities, improving public health and the environment, and improving the health, welfare, and performance of swine production.

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