Poultry farms can bring many pollution problems. Therefore, it is important to maintain optimal conditions for poultry production and also it should not impair the human and animal environment through the emission of harmful gases. To be profitable, farmers must use the best practices and technological advances in order to achieve the most advantageous environment.
The impact on the ecological systems may result from the direct release of detrimental constituents into the atmosphere or indirect deposition of these constituents into groundwater. The environment in the poultry housing is a combination of physical and biological factors which interact as a complex dynamic system of social interactions, husbandry system, light, temperature and the aerial environment. The high stocking density in the modern poultry barns may lead to reduced air quality with high concentrations of organic and inorganic dust, pathogens and other micro-organisms as well as harmful gases such as ammonia, nitrous oxide, carbon dioxide, hydrogen sulphide, and methane. The production and emission of gases in poultry or any livestock facilities involve complex biological, physical and chemical processes. The rate of emission is influenced by many factors, such as diet composition and conversion efficiencies, manure handling practices and environmental conditions.
The composition of poultry diet and the efficiency of its conversion to meat or eggs affect the quantity and physical and chemical properties of the manure. Manure handling practices and environmental conditions also affect chemical and physical properties of the manure, such as chemical composition, biodegradability, microbial populations, oxygen content, moisture and pH. Most gaseous pollutants originate from the breakdown of faecal matter and the concentrations depend on the ventilation efficiency and rate, as well as the stocking density and movements of the animals. The litter type, management, humidity and temperature affect the gas concentration and emission from broiler fattening. Also, commercial egg production facilities involve a variety of housing systems and manure handling practices, which can produce different magnitudes of environmental footprint. However, research information concerning the environmental pollution for various production systems and the system’s ability to maintain the microenvironment that is conducive to poultry welfare and health, conservation of natural resources and production efficiency is not very clear.
AMMONIA: Ammonia (NH3 ) is the primary basic gas in the atmosphere. Elevated concentrations of NH3 in poultry barns reduce feed intake and impede bird growth rate, decrease egg production, damage the respiratory tract, increase susceptibility to Newcastle disease virus, increase the incidence of air sacculitis and keratoconjunctivitis and increase the prevalence of Mycoplasma gallisepticum .Egg quality may also be adversely affected by high levels of atmospheric ammonia as measured by reduced albumen height, elevated albumen pH and albumen condensation .The ammonia concentration in the air plays an important role in the neutralisation of atmospheric acids generated by fossil fuel combustion. The reaction product forms a NH4 + aerosol, which is a major component of atmospheric particulates. These NH4 + particulates may be transported long distances from the production site before returning to the surface by dry deposition or precipitation. Animal production produces a significant component of anthropogenic NH3 emissions. Ammonia is also a component of odour . Ammonia volatilisation from manure materials within poultry barns can adversely affect production, and also represents a loss of fertiliser value from the spent litter. It is generated during bacterial decomposition of protein and urea in housing areas and during storage and application of excreta under aerobic and anaerobic conditions .The main source of NH3 is urine of animals. Seventy percent of nitrogenous substances in excrement originate from urine and 30% from feaces. Poultry feaces contain 60−65% of uric acid, 10% of ammonia salts, 2−3% of urea and remains of creatinine. Especially uric acid is rapidly changed by the microbes to NH3 .Gaseous NH3 is the predominant pollutant in poultry systems. Higher concentrations adversely affect bird performance, welfare and human health.. It is highly reactive and deposits readily to vegetation and other surfaces close to its source.
GREENHOUSE GASES: In animal housing there are several factors that affect the production and release of harmful gaseous compounds. These are primarily the number and live weight of housed animals, floor surface covered with their excrements, manure storage time in housing area, performance of ventilation system, air temperature, year season, air movement above the litter surface or not bedded barn floor, air penetration through the litter, litter temperature, moisture, pH, the C:N ratio and feed composition . Much of the greenhouse gases (GHG) generated from the poultry industry is primarily from feed production .Numerous factors affect the emission of these gases from broiler facilities. The results showed that 90% of the emissions from the broiler and pullet farms were originally from propane and diesel gas use, but only 6% from laying hen farms. On laying hen farms, about 29% of GHG emissions were the result of electricity use while the pullet and broiler farms had only 3% emissions from electricity use. Emissions from manure management in the layer facility were responsible for 53% of the total emission from the facility, while electricity use represented 28% of the total emissions.
METHANE: Methane (CH4 ) is greenhouse gas with high global warming potential, which is 23 times the greenhouse effect of carbon dioxide. Due to the digestive physiology, poultry are monogastric and produce only slightly amounts of CH4 (Pedersen et al.,2008). However, methane can be generated in the animal housing, manure storage and during manure application, by fermentation of organic matter .A similar microbial process to enteric fermentation of ruminants also leads to methane production from stored manure. Additionally, small amounts of methane are produced from manure deposited on grasing lands .However, it is not well understood whether considerable amounts of CH4 may be emitted from litter reactions inside the building, depending on the litter management and conditions.
NITROUS OXIDE: Nitrous oxide (N2 O) is a very potent greenhouse gas, with 310 times greater global warming potential than carbon dioxide .N2 O in the atmosphere has a long life and contributes significantly to global warming. It is converted to NO, which decomposes stratospheric ozone that protects Earth from harmful ultraviolet radiation .This gas is related to the agricultural nitrogen cycle. Excess nitrogen in agriculture systems can be converted to nitrous oxide through the nitrification–denitrification process. N2 O can be produced in soils following inorganic and organic fertilizer application and also from manure storage surfaces.. Nitrous oxide is generated by the microbial conversion of nitrates in excreta during their storage and applications .The production of N2 O from poultry manure depends on feaces composition, microbes and enzymes involved and the conditions after excretion.
CARBON DI OXIDE: The main source of carbon dioxide in livestock is animal respiration, combustion of natural gas for heating and cooking, and decomposition of organic matter. The high emission from propane use in broiler and pullet houses due to heating the houses during brooding and cold weather. There is also a link between metabolism and animal production of CO2 .Carbon dioxide production by birds is proportional to their metabolic heat production, and thus to the metabolic body weight of the birds, which in turn is affected by the temperature and bird activity. The animal CO2 production under normal farm conditions has normally a diurnal variation of ±20%
Mitigation strategies to minimize environmental impacts include nutritional strategies, the primary being to minimize the feeding nutrients in excess of dietary needs, ventilation and manure management. The various mitigating strategies are of discussed briefly.
1.HOUSING MANAGEMENT:Traditionally improving air quality in poultry houses has been largely accomplished through ventilation. Increased ventilation reduces pollutants within the poultry house but translate directly into higher emissions. Ventilation is therefore, more of in house air quality control method then a strategy to inhibit the formation and poultry emissions.
2. HOUSE CLEANING: It is a simple technique of reducing dust emissions from poultry buildings. Regular house cleaning, including vacuuming and power washing between flocks, reduces the volume and potential for contamination of the air in the house as well as air exhausted from the building remove litter or manure, dry clean, wet wash, disinfect, and thoroughly clean and disinfect the feeding and drinker systems and then allow enough downtime. Regular sweeping and vacuuming of poultry houses in locations where dust, feathers, and dander collect, would likely improve air quality for birds and farm workers as well.
4. OIL AND WATER APPLICATION: Oil can be applied both manually with a handheld sprayer or automatically using a permanently installed sprinkler system. It is important that droplet size is not too large, resulting in poor oil distribution, or too small, which may be a health hazard. Ultrasonic sprayer generating 7-150μm diameter particles with a 2% solution of emulsified canola oil significantly reduces dust by 47%. The oil and water mixtures reduced dust concentrations approximately 50%, whereas the pure water application reduces dust to about 30%.
5. OZONATION: Ozone (O3) is a powerful oxidizing agent and a natural germicide.
6. VEGETATIVE SHELTER BELTS: Strategically planting trees, shrubs, and other vegetation around poultry houses offers several potential benefits. Trees, shrubs, and other vegetative materials strategically planted around poultry houses have the potential to foster better neighbor relations by filtering dust, feathers, odour, and noises. Potential environmental benefits include reduced atmospheric ammonia loss, providing a visual screen from routine activities and enhancing the public’s perception of the industry and also reduce surface and groundwater contamination. It also acts as windbreak and a source of shade to reduce seasonal temperature extremes and as a filter for airborne pathogens for improved biosecurity.
6.BIOFILTERS: Biofilters are those that filter dust, ammonia, hydrogen sulfide, and other undesirable odours in poultry houses. The material is usually organic in nature with a resident microbial film that helps in degradation of gases and odors in addition to its trapping function. The contaminants are then oxidized to produce biomass, carbondioxide, water and inorganic salts. Straw, compost, and woodchips are good filter materials as long as particle size (>20 mm) and porosity is maintained for good airflow. Biofilters should be placed near exhaust fan so that the exhausted air from poultry house directly enters into these filters through the fan. Hence contaminants will get reduced. Humidifier must be placed between these two so as to maintain optimum moisture level in biofilters.
7.WATER FILTERS: By utilizing water as a scrubbing media, these filters trap emissions in them. These systems have been used for control of industrial air pollution and have the potential to scrub dust, ammonia, sulfur compounds, and nitrous oxides from poultry houses. Two channel water filters made of cellulose material, with water flowing from top to bottom through the first channel and gets acidified water and flows through the second, provides better air trapping.
8.WIND BREAKS: It is a simple strategy of enhancing the dispersion of dust and odour on a local scale with the use of natural and artificial windbreaks. They reduce dust and odour downwind by both dropping particulates and lifting emissions into the upper air stream for greater dispersion and dilution. Natural windbreaks comprised of trees and shrubs take 3 to 10 yr to grow, offer visual protection for the farm, and also trap particulates and odour.
9.ELECTROSTATIC PRECIPITATION: Electrostatic precipitation or air cleaning is a technique of removing the air particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators/ air cleaners are highly efficient filtration devices that minimally impede the flow of gases through it, and can easily remove fine particulate matter such as dust and smoke from the air stream. This device generates negative gas ions which bind to incoming air or dust particles that make these negatively charged particles to get captured on a positively charged plate in the device. Hence, the resulting air from the precipitator is pure and filtered. The implantation of this device in poultry houses reduces 60% airborne dust; 76% total bacteria and 56% ammonia. In caged layer houses, around 36.6 to 65.6% reduction in airborne dust can also be achieved, which provides a comfortable environment to birds and humans too.
Use of chemical additives : These chemicals have been classified into two categories: those that act to inhibit microbial growth (which would slow uric acid decomposition) and those that combine with and neutralize ammonia (Carlile, 1984). Odour and moisture absorbents typically are clay-based products containing zeolites; hydrous silicates that can act as ion-exchangers and absorbents. By lowering the moisture content of poultry manure and litter, absorbents inhibit the microbial activity associated with the formation and volatilization of NH3.
Compounds like aluminium (Aluminium sulfate-alum, Aluminium chloride), Calcium and iron-containing compounds (ferric chloride, ferrous sulfate), zeolites like clinoptilolite, antibiotics, potassium permanganate, hydrogen peroxide, sulfuric acid, chlorine, yucca saponin, sodium bisulfate, phosphoric acid, superphosphate, formaldehyde, hydrated lime, lime stone, gypsum, zinc sulphate, copper sulphate, magnesium sulphate, and manganese chloride reduce microbial uricase activity thereby reducing environmental pollution. Alum application in litter also reduces ammonia emissions. Zinc sulfate is most effective in reducing manure pH and the growth of uric acid utilizing bacteria. On addition to fresh manure, ZnSO4 reduces ammonia volatilization and increases total nitrogen retention by almost two-fold. Dietary supplementation of Zn can also reduce ammonia losses and also increase total nitrogen retention.
Organic acids are another choice to acidify litter and reduce ammonia volatilization. Litter can be treated with 5% citric acid, 4% tartaric acid, or 1.5% salicylic acid and it reduces litter pH below 5, both litter and air ammonia concentrations, and also inhibits the growth of E. coli, Salmonella enteritidis, Proteus, and Pseudomonas sp.
Various extracts of the yucca plant are claimed to reduce ammonia levels in poultry houses. A soluble component of the yucca plant seems able to bind ammonia, preventing its release from manure, which is especially important in confinement housing systems. Most poultry will react adversely to 50 ppm ammonia, and this is in contrast to the level of 20-30 ppm which is the usual detection range for humans.
Nitro-compounds such as nitrothane, nitrothanol, nitropropanol, and nitropropianic acid have potential to reduce ammonia volatilization in poultry manure acid–utilizing microorganisms. 2-nitro-1-propanol exhibits bactericidal tendencies that inhibit the production of several foodborne pathogens such as Salmonella typhimurium, Campylobacter jejuni, Listeria monocytogenes, and Escherichia coli O157:H7. Amendments with nitrifying bacteria have the potential to reduce manure NH3 and NH4 levels as bacteria oxidize them to nitrite and nitrate, NO2 and NO3. Raking of litter must be done regularly to ensure proper mixing of these additives in litter and also to remove any buildup of moisture.
11.COMPOSTING: Composting of poultry litter, at the right moisture, carbon:nitrogen ratio, and temperature with proper aeration can reduce ammonia losses and retain fertilizer value. Using wheat straw and peat reduced ammonia losses by 33.5 and 25.8%, respectively in composting of poultry manure. Zeolite is a more effective NH3 (or NH4) adsorbent than soil and reduces NH3 losses by 60%. Zeolites, calcium and aluminum salts, and acidifiers also improve nitrogen retention and reduce ammonia volatilization.
12.FEEDING MANAGEMENT: Dietary strategies mainly aim at nutrient reduction, particularly dietary protein content, which can result in a reduction of NH3 formation. Feeding of low protein diets result in reduced N excretion and subsequent NH3 volatilization. Other dietary manipulation strategies include feed formulation based on amino acid requirements rather than crude protein; optimizing the dietary amino acid profile with bird requirements, phase feeding for current growth and production; selection of feed ingredients with low nutrient variability to reduce protein margins of safety; and use of feed enzymes and additives. Supplementation of diets with an enzyme cocktail, significantly improved protein digestibility, as well as the digestibility of starch, fat, and energy.
Better accounting for ingredient CP, amino acid variability, and digestibility can reduce over-formulation and N excretion. Immunize birds against the enzymes responsible for ammonia formation. Jackbean urease enzyme is of most importance. On injection into hens, it develops antibodies to the enzyme and passes them on as maternal antibodies to their chicks. Hens can also be immunized with microbial uricase and produce high levels of uricase-specific antibodies in the egg yolk. These antibodies (IgY) have the potential as manure amendments or as a dietary supplements to reduce the breakdown of uric acid to urea. It also prevents harmful effects of ammonia in the intestinal tract.
13.USE OF DIRECT FED MICROBIAL: Complex cultures of multiple organisms tend to demonstrate greater efficacy in augmenting BW gain than specified single or few strains. It also reduces mortality in chickens receiving 0.10% Lactobacillus culture, from 8.2% in control birds to 3.2%.
14. MINIMIZE FEED AND WATER WASTE:In general, N and P content in the manure will increase by 1.5% for each 1% increase in feed waste. Poor feeder design and positioning and feed form can result in significant animal feed waste, which ultimately ends up in manure or litter. Poultry will also waste a significant amount of feed if feeders are overfilled, adjusted too low, or poorly designed (Beyer et al., 2001). Small birds will climb into feeders and scratch out feed, and larger birds will fling feed out with their beaks or bills if the feeder is poorly designed or adjusted. Hence feeder height should be adjusted such that the top of the feed pan is level with the base of the bird’s neck, and the feed fill level to only 25% of the feeder pan.
Water also affects the amount of minerals emitted, but it will adversely affect manure or litter processing and disposal costs. It can also lead to an increased incidence of pests (bacteria, litter beetles, flies, etc.), ammonia emission, and air quality problems, thereby affecting volume and nutrient quality of the litter to be disposed.
15. FEED MANUFACTURING: Feed manufacturing technology can have a significant impact on minimizing nutrient emissions poultry operations by producing the feed in a form that reduces waste and improves the digestibility of the feed. Fine grinding and pelleting feed are effective ways to improve feed use and decrease DM and nutrient excretion. By reducing the particle size, the surface area of the feed ingredient particles is increased, allowing for greater interaction with digestive enzymes.
16. FEED FORMULATION: Since birds can excrete all of the minerals they are unable to assimilate as tissue growth, estimation of accurate of nutritional requirements is essential to optimize dietary nutrient balance and to minimize mineral emission.
17.ESTIMATING AMINO ACID REQUIREMENT BY IDEAL PROTEIN CONCEPT: Understanding amino acid utilization for protein synthesis and maintenance are critical to the formulation of an accurate ideal protein profile and thus for minimizing N excretion. Thus, the ideal protein concept can play an integral role in animal production, particularly as non-traditional protein containing ingredients become increasingly available. All of the indispensable amino acids are expressed as a percentage of lysine, which is the reference amino acid. Using an established set of ideal ratios of other indispensable amino acids to lysine, it is possible to formulate an ideal protein without having to independently establish requirements for each indispensable amino acid.
18.GENETIC MODIFICATION OF GRAINS AND OILSEEDS FOR BETTER NUTRIENT AVAILABILITY: Understanding amino acid utilization for protein synthesis and maintenance are critical to the formulation of an accurate ideal protein profile and thus for minimizing N excretion. Thus, the ideal protein concept can play an integral role in animal production, particularly as non-traditional protein containing ingredients become increasingly available. All of the indispensable amino acids are expressed as a percentage of lysine, which is the reference amino acid. Using an established set of ideal ratios of other indispensable amino acids to lysine, it is possible to formulate an ideal protein without having to independently establish requirements for each indispensable amino acid.
CONCLUSION:For the poultry industry, concerns about poultry emissions especially ammonia are multifaceted and include issues of live production performance, animal health, and welfare, and environmental impact. Bird performance and health can be affected by both respiratory disease challenge and physical damage due to high ammonia concentration. Hence efficient management procedures should be concerned to mitigate these emissions from poultry production for the well being of humans and animals.