Brajen Singh Kshetrimayum
Senior Consultant – Poultry Medicine.
In poultry raising, one of the biggest social complaints apart from flies is the smell of the manure. The ammonia buildup is a prevalent issue, their high concentration in poultry houses not only smell bad, it’s also a health hazard for the birds in the shed and the humans working with them. Ammonia is an invisible, colorless, pungent smell, water soluble alkaline gas produced when organic matter like chicken droppings and urine decomposes. Reduced ammonia emission helps alleviate a number of health problems like ascites, gastrointestinal irritation, respiratory diseases, dermatitis and foot burns.
Ammonia formation in poultry litter
Ammonia is a natural byproduct of manure. The decomposition of nitrogen compounds in manure results in ammonia and ammonium formation. These two products are in equilibrium related to manure pH. Lower pH favors the ammonium form which is not release as gas (ammonia) but stays in solution in the poultry litter. Decreasing litter pH, moisture and temperature will lower ammonia release. However, a slight 5% increase in litter moisture from 20-25% at 75 degree F results in a 140% increase in ammonia.
Nitrogen is a component of poultry diets via protein or other sources. Some of this nitrogen are used by the chicken and is incorporated into tissues or eggs, but 70-80% of the nitrogen fed to birds are excreted as uric acid, ammonia 10% and urea 5% into the litter. The uric acid and urea are converted into ammonia through microbial urease enzyme found in the manure in the presence of water and oxygen. Due to the ionic state of ammonia (lack of ionic charge) – it is readily release into the air. Ammonia is a water soluble gas, can be dissolved in the moisture of eyes, in the lining of the respiratory tract, on the skin and oral cavities.
Inadequate litter management and poor ventilation results in wet litter leading to ammonia buildup in poultry houses. Overcrowding and high humidity also contribute to the accumulation of ammonia. Factors that influence ammonia formation and its release into the shed also includes litter type, bird activity, manure handling and frequency of removal. Some of the factors influencing how manure bacteria and enzymes break down nitrogen to form ammonia includes nitrogen content, temperature, humidity and pH.
Ammonia, poultry health and performance
Most people, according to Occupational Health and Safety Administration (OSHA), can detect ammonia at a level of 5 ppm and they limits human exposure to a maximum of 50 ppm over an 8 hour workday. Experts recommend a maximum of 25 ppm ammonia level in poultry houses, while more conservative recommendations suggest a limit of 10 ppm. Prolong exposure to high level of ammonia can lead to chronic respiratory problems such as bronchitis and asthma in humans.
High level of ammonia in poultry sheds result in poor bird performance, health and loss of profit to growers. This suffocating pungent odor gas irritate the eyes and respiratory system. Ammonia gas when dissolved in the moisture of eyes, the respiratory tract and other moist tissue surfaces, reacts with water molecules and form ammonium hydroxide – a caustic substance that burns or destroys living tissues leading to respiratory damage. The ammonium corrodes the lining of chicken respiratory tracts, destroy the cilia of epithelia cells of eyes and nasal mucosa.
When the accumulated mucus on the tracheal mucosa is unable be cleared by the cilia, bacteria gets trapped, finally reaching lungs and air sacs causing infections. Some observable changes associated with ammonia toxicity in poultry are difficulty breathing, irritation of trachea, air sac inflammation and conjunctivitis. The tracheal mucosa may become devitalized due to high incidence of airsacculitis, pneumonia and septicemia caused by E.coli in chickens that have been exposed to high ammonia levels.
Birds exposed to 20-25 ppm of ammonia throughout production had increased susceptibility to secondary bacterial and viral challenges, poorer appetite, reduced body weight, decrease feed efficiency, more E. coli infections, infectious coryza and higher mortality. In layers the consequences of prolonged exposure to ammonia could be more devastating since pullet performance as layers is in question. Chronic exposure to ammonia may impair egg production. There is reduction in antibody titers to Newcastle disease virus when layers and breeders were persistently exposed to 25 ppm ammonia within the shed.
In poultry, high level of ammonia exposure over three weeks decreased the intestinal surface area impacting nutrient absorption, more susceptible to oxidative stress and lower immunity. Harmful effects of various ammonia concentrations on human:
- 5 ppm – Lowest detectable level
- 6 ppm – Eye and respiratory irritation
- 11 ppm – Reduced animal performance
- 25 ppm – Maximum exposure level allowed for 1 hour
- 35 ppm – Maximum exposure level allowed for 10 minutes
- 40 ppm – Headache, nausea and loss of appetite in humans.
- 50 ppm – Reduce performance and health, increase possibility of pneumonia.
- 100 ppm – Sneezing, salivation and irritation of mucus membranes.
- 300 ppm – Threat to human life and health.
Common clinical signs of prolong exposer to higher concentrations of ammonia on eyes of the birds are irritation, conjunctivitis and corneal damage. Swelling and reddening eyelids, conjunctiva and nictitating membrane. Eyes may become almond shaped and affected birds have more risk to swollen head syndrome in respiratory viral infections. Ammonia blindness in chicken is characterized by cloudiness and opaqueness of the eyes, which can lead to complete blindness that is mostly accompanied by eye discharge, squinting and redness. It is cause by ammonia fumes coming out from poorly managed litter in an ill ventilated house. Blind chicken may have difficulty finding food and water, navigating their interaction with other chickens. Effects of ammonia in different concentrations on chickens are:
- 20 – 30 ppm: No drop in egg production and weight loss. Slight respiratory lesions.
- 50 – 60 ppm: No change in egg production, lower feed intake, weight loss, respiratory and eye lesions visible.
- 100 – 200 ppm: Reduce egg production, severe weight loss, ammonia blindness (kerato-conjunctivitis), loss of cilia from respiratory epithelium, increased number of mucus secreting cells, hemorrhages in trachea and bronchi. Heart rate and breathing affected.
Measure ammonia in poultry houses
Monitoring ammonia levels in poultry sheds is crucial for chicken health and workers safety. These methods includes – chemical test kits, gas sensors and ammonia meters. To check ammonia level in poultry house physically, squat and bend down head one foot above the litter. Breathe normally for a moment or two. Burning sensation of eyes, nose and throat indicates too high a level of ammonia for the birds. Recovery is rapid on removal of the excess gas.
- Chemical test kits: It is simple, inexpensive, efficient and easy to use. Results can be obtained quickly. However, they are less accurate and not suitable for continuous monitoring.
The test kits involve taking samples of the litter or air in the poultry house using chemical solution to determine the level of ammonia.
- Gas sensors: are electronic devices that detect the continuous presence of ammonia in poultry manure. The method is expensive, require regular maintenance and calibration.
- Ammonia meters: specialized devices providing accurate and minimum ammonia levels in poultry house on real time monitoring basis. However, the process is expensive and also needs regular calibration and maintenance.
- Electronic nose technology (ENT): a relatively new very sensitive approach, using a sensor array to detect and identify the volatile organic compounds produced by ammonia. ENT detect low level of ammonia very fast and can provide real time monitoring of ammonia levels.
- Detector tube: Easy to use inexpensive instruments for measuring ammonia level in poultry environment with reasonable accuracy is Colorimetric Tube, also called Detector Tube. The pen sized glass tube changes color along its length after exposure to ammonia gas indicating the concentration of ammonia when color stop changing. Two main colorimetric tubes are Pull tubes and Diffusion tubes.
Reducing ammonia level and odor in poultry environment
In poultry production, conditions that exacerbate ammonia level include diets with excess nitrogen, high relative humidity, high temperature, wet litter, basic pH in the manure and poor ventilation. Reused litter and delayed removal of manure and slurry increase ammonia level.
- A well balanced diet with highly digestible ingredients and functional feed additives can improve the digestibility of nutrients in small intestine. Poultry diet management is the most important preventive measure. Nitrogen within the poultry manure can be reduced by formulating diets based on amino acid requirement instead of crude protein. Reducing dietary protein by 5% could lower 60% or more nitrogen excretion in broiler and laying hens. Further decreases in the protein levels of the diet require that all essential amino acids are carefully balanced and included, preferably in a crystalline form. If the protein level in the diet decreases by 3%, there will be an 8% less water consumption resulting in drier litter and ammonia in the air. Keeping the gastrointestinal tract healthy and functional reduce the excretion of undigested and unabsorbed feed in the feces minimizing ammonia volatilization within the poultry house. Reducing nitrogen excretion and emissions in poultry manure by nutritional strategies is important to maintain a clean environment.
- Phytogenic feed additives (PFA) increase digestibility of nutrients within the gastrointestinal tract, and also reduce gut inflammation from stressors. PFA modulate gut microbiota and minimize the harmful effects of pathogenic bacteria on the gut leading to lesser nitrogen excretion from the birds to the environment.
- Dietary fiber decrease ammonia emission. Inclusion of soy hulls, wheat middling or corn in the diets of laying hens reduce the total ammonia emission by 50%. Inclusion of corn DDGS at 10%, Wheat middling’s at 7.3% and soybean hulls at 4.8% in layer diet decrease ammonia emission by 41, 38 and 27%, respectively from the manure. This result has been attributed to a shift in the partition of nitrogen excretion from uric acid to microbial protein and reduction in manure pH from an increased content of microbial produced volatile fatty acids causing a shift from ammonia to the more water soluble ammonium thus reducing ammonia emission.
- Feed processing affect nutrient availability and gas emission. Reducing feed particle size from 1000 to 600 microns increases dry matter and nitrogen digestibility by 5-12% and lower nitrogen in manure by 20-24%. Avoid excessive grinding which otherwise may cause gut motility and health problems.
- Feed additives like the zeolite and diatomaceous earth will bind ammonia in feces and prevent being emitted into the air. Acidification of the diet alleviate ammonia production as acidic manure convert ammonia to ammonium which is water soluble and not emitted in air. This can be achieved by adding gypsum (CaSO4) or calcium benzoate and also through lowering the dietary electrolyte balance. Bentonite is another clay that binds ammonia and urates.
- Extracts from desert plant Yucca schidigera reduce blood urea and blood ammonium ions, reduce excessive nitrogen breakdown in the ceca and bind ammonia. Yucca extract spray over the manure also control ammonia odor. Addition of brands like De-Odorase or Sapodo @ 75 – 150 gm per ton feed reduces environmental ammonia level by 20-30% with improve growth and reduced mortality. Sapodo has two active components – saponins and glycocomponents. Saponins are surfactants and reduce surface tension, thereby enhance nutrient absorption, improve digestion and microbial activity within the GIT, while, glycocomponents directly binds ammonia in the digestive tract and environment thus prevent offensive odor generated by the manure.
- Poultry litter treatment with sodium bisulfate converts ammonia to ammonium a great food source for plants and won’t emit noxious gases. Keeping litter moisture between 20-25% prevent ammonia formation. Alum application in litter reduces ammonia emission. Zinc sulfate is very effective reducing manure pH and the growth of uric acid utilizing bacteria. When added to fresh manure, zinc sulfate reduces ammonia volatilization. Dietary supplementation of Zn can also reduce ammonia losses and increase total nitrogen retention.
- Organic acids like 5% citric acid, 4% tartaric acid and 1.5% salicylic acid when treated with litter, they reduces manure pH below 5, both litter and air ammonia concentrations, inhibit the growth of E.coli, Salmonella, Proteus and Pseudomonas organisms.
- Proper ventilation to keep the manure dry avoid converting uric acid into ammonia. Adequate ventilation to remove moisture and reduce humidity in the poultry house is the most effective method of ensuring good air quality.
- Managing the bird diet to avoid increased nitrogen in manure due to higher complex protein that does not properly break down or absorbed. This can be prevented by balancing the protein or amino acid levels in the diet and ensuring gastrointestinal health.
- Minimizing feed and water waste. Poultry will waste a significant amount of feed if feeders are overfilled. Adjust the feeder height for the type of feeder and fill only 25% of the feeder pan. Fecal nitrogen may increase by 1.5% for each 1% feed waste. The nipple drinker system should be adopted for better control over water intake and wastage.
- Composting of poultry litter under right temperature with proper aeration at perfect moisture, carbon: nitrogen ratio can reduce ammonia losses and retain fertilizer value.
- Adequate floor space should be provided according to age group and type of birds. Dense population will lead to wet litter and more ammonia production.
- Improve nutrient digestibility by supplementing diets with enzymes, probiotics and prebiotics.