Harm of Ammonia to Livestock and Poultry Farming and Corresponding Countermeasures (Part 1)

        As livestock production continues to scale up and intensify, the amount of ammonia emitted by livestock and their waste is steadily increasing, making it a major source of air pollution. According to measurements, a poultry farm with a flock size of 720,000 birds emits 13.3 kilograms of ammonia per hour, while a pig farm producing 100,000 pigs annually releases 159 kilograms of ammonia into the atmosphere every hour [1]. In the United Kingdom, the Netherlands, Denmark, and Germany, ammonia emissions from animal husbandry account for 75%, 85%, 82%, and 76% of the countries’ total emissions, respectively [2]. In the United States, more than 80% of ammonia emissions originate from livestock farming. Globally, ammonia emissions from livestock production account for approximately 50% [3]. Ammonia pollution not only impairs the normal growth of livestock and poultry, triggers various diseases, and causes severe economic losses to the livestock industry, but also poses risks to human health. Currently, as farming environments continue to deteriorate, air and water pollution in farms are becoming increasingly serious, and outbreaks of disease are on the rise—particularly affecting small- and medium-sized farmers who face low profitability. Faced with this situation, how can we adopt a series of measures to reduce ammonia generation and emissions? Many scholars have proposed the concept of “green, environmentally friendly, and safe” ecological livestock farming, aiming to achieve harmonious and sustainable development between humans and nature. This approach has become a key focus for both livestock farmers and researchers.

1. Production and Hazards of Ammonia

1.1 Production of Endogenous Ammonia in Livestock and Poultry Under normal circumstances, there are three main pathways for the production of ammonia in the blood of livestock and poultry: first, the deamination of amino acids within the body; second, the deamination of purines and pyrimidines; and third, the absorption of ammonia from the digestive tract. However, under conditions of high ammonia concentrations in livestock and poultry housing, animals can absorb ammonia through their respiratory tracts. This ammonia directly enters the bloodstream via the alveolar epithelium. A portion of the absorbed ammonia is converted into uric acid by the liver, while another portion remains in the bloodstream, causing an increase in blood ammonia levels. Elevated blood ammonia levels reduce the blood's oxygen-carrying capacity, leading to hypoxia in animals and triggering diseases of the respiratory and metabolic systems.

1.2 Production of Exogenous Ammonia from Livestock and Poultry The source of exogenous ammonia is the decomposition and decay of organic materials such as accumulated manure, urine, feed residues, and bedding. Ammonia production is accelerated under conditions of moist bedding, appropriate pH levels, high temperatures, abundant fecal matter, and sufficient air circulation. The concentration of ammonia in livestock and poultry houses depends on factors including house temperature, stocking density, ventilation conditions, floor structure, management practices, and the frequency of manure removal. Since ammonia is highly soluble in water, its concentration tends to be relatively higher in humid air. According to reports, a pig weighing 50–80 kg produces 6 kg of feces and urine per day, containing 16–37 g of nitrogen, of which about 60% consists of substances such as urea or ammonium salts that readily convert into ammonia [2].

2. Hazards of Ammonia 　

Ammonia has very high solubility in water— at 20°C, 1 liter of water can dissolve as much as 700 liters of ammonia. It is a highly irritating gas with the following major hazards: (1) It irritates mucous membranes, easily triggering various inflammatory responses, particularly strong irritation of the respiratory tract, which can readily lead to respiratory diseases. (2) It significantly affects the growth performance of livestock and poultry. (3) It impairs the effectiveness of vaccine immunization, thereby reducing the resistance of livestock and poultry. The extent to which ammonia affects animals depends on its concentration and the species of animal involved. Generally speaking, ruminants have a higher tolerance to ammonia than monogastric animals, and pigs, in turn, are more tolerant than chickens.

2.1 The Effects of Ammonia on Livestock and Poultry

2.1.1 The Impact of Ammonia on the Disease Resistance of Livestock and Poultry

Ammonia is a well-recognized stressor and one of the most harmful gases found in animal housing facilities. Once absorbed into the bloodstream via the digestive tract, ammonia from the environment enters the blood through the respiratory system, where it binds to hemoglobin, converting it into methemoglobin. This reduces hemoglobin's oxygen-carrying capacity, impairs the blood's buffering capacity, and diminishes hemoglobin's oxidative properties, leading to anemia and tissue hypoxia, thereby weakening the body's resistance to disease.

An aqueous solution of ammonia is strongly alkaline and irritating to mucous membranes. In severe cases, it can cause alkali burns, leading to symptoms such as tearing and burning in the eyes, inflammation of the cornea and conjunctiva, and visual impairment. It may also trigger coughing, tracheitis, bronchitis, pulmonary edema, bleeding, difficulty breathing, and asphyxia—potentially even tissue necrosis, thereby disrupting respiratory function. Furthermore, when ammonia dissolves into the mucus of the respiratory tract’s mucous membranes, it raises the pH of the mucus toward alkalinity, impairing the motility of cilia and increasing susceptibility to airborne diseases.

The impact of different ammonia concentrations indoors on poultry health varies (see Table 1). As the ammonia concentration in chicken houses continues to rise, its irritant effect intensifies, often leading to conditions such as keratitis, conjunctivitis, dermatitis, atrophy of the bursa of Fabricius, air sac inflammation, and colibacillosis in broilers. When chickens are exposed to an ammonia environment with a concentration of 20 mg/L for an extended period, they exhibit tearing, loss of appetite, and weight loss. At a concentration of 1,000 mg/L, tearing and photophobia become apparent within three days; within eight days, the corneas turn white, ulcers appear on their surfaces, air sac inflammation develops, and severe coccidiosis sets in. Due to reduced feed intake, even low concentrations of ammonia can result in poor growth and development, delayed sexual maturity, decreased egg production, and increased mortality rates.

Table 1 room The Impact of Different Ammonia Levels on Poultry Health

2.1.2 The Impact of Ammonia on the Growth Performance of Livestock and Poultry

Ammonia can stimulate rapid growth and metabolism in mucosal cells, thereby increasing the demand for oxygen and energy. At the same time, the detoxification of ammonia is a highly energy-consuming process. As a result, animals have less energy available for growth and production, which in turn affects their growth performance. Song Yi [5] ( 2008 ) and other experiments have found that broiler chickens in 0 ~ 3 Zhou Shi 52mg/kg At higher ammonia concentrations, feed conversion rates can be significantly reduced, and mortality rates tend to increase as ammonia concentrations rise. Furthermore, broiler chickens... 80mg/kg At certain ammonia levels, fowl ascites syndrome can be induced in broilers. Based on the trends in ammonia concentration and broiler production performance, it is believed that modern broilers... 0 ~ 3 The ammonia concentration in the housing facility should not exceed. 13mg/kg , in 3 ~ 6 The ammonia concentration in the housing facility should not exceed. 20mg/kg Zhao Lirong’s research indicates that : When the ammonia concentration inside the chicken coop exceeds 78.3mg/kg At that time, the egg-laying rate declined. 43.1% The relationship between ammonia concentration in chicken houses and egg-laying rate is negatively correlated and highly significant. [6]

Table 2   The Impact of Ammonia Concentration on Broiler Production Performance [7] (Wang Zhong, 2008 )

Cao Jin [7] Studies have shown that the daily weight gain of pigs decreases as the ammonia concentration in pig houses increases, while the feed-to-weight ratio rises with increasing ammonia levels in pig houses. Moreover, high ammonia concentrations can also trigger other diseases.