Ammonia gas in poultry houses seriously affects the health condition of the birds. Good litter management and ventilation will minimise the level of ammonia, improve productivity, reduce the likelihood of respiratory diseases, improve the birds’ welfare and provide a pleasant, safe environment for workers.
Ammonia is a gas present in the atmosphere of every poultry house. It results from the chemical decomposition of uric acid in droppings by certain bacteria in the litter. It is particularly high in houses where the same litter is used for successive flocks. The main factors affecting atmospheric ammonia concentration in poultry houses are litter conditions and air movement (ventilation). Moisture content, pH and the temperature of the litter, influence the degradation of uric acid by bacteria. Poor ventilation, loose droppings and faulty, overfilled or low positioned drinkers, are common causes of wet litter in poultry houses.
Farmers mostly use for litter on the floor like rice husk, pine ss, wood dust ss, sawdust, hay, straw and silicon sand material etc as per the local availability and their low economic value.
One of the most basic principals of the digestive system is that what goes in must come out. The chemical & physical composition of litter is highly variable due to differing bird species, diets, bedding retention times and other farm management practices.
Hard fibre litter materials have been demonstrated to improve gizzard development and improve feed conversion efficiency, without any effect on feed intake or weight gain. Poultry litter is broadly comprised of protein, carbohydrate, lipid & fats, with carbohydrates responsible for the majority of Biodegradable materials in the form of cellulose, starch & sugar and loaded with beneficial as well as pathogenic bacteria and fungus.
Monitoring litter health is an essential parameter of poultry flock health because most gaseous pollutant originates from the breakdown of faecal matter which intensifies with the growing ratio of moisture, temperature and pH level. High level of ammonia in poultry house can result in poor bird performance & health and loss of profit to the grower or integrator. Uric acid & organic nitrogen ( in the bird excreta & spilt feed are converted to Ammonium (NH4) by the microbes in the litter. Depending on the moisture content, temperature and high pH of the litter, a portion about one-third of Ammonium will be converted into ammonia (NH3).
Ammonia is a pungent gas that irritates the eyes and respiratory system and can reduce re¬sistance to infection in poultry. At high-enough concentrations (above 10 ppm), ammonia will reduce feed efficiency and growth while increasing mortality and carcass condemnations. The result is an economic loss to the grower and integrator. Moreover, now a day litter is re-used for succeeding broiler flocks to reduce the running cost since bedding/litter material has become costlier these days, so there will be greater environment stress and challenge to control ammonia problem.
The poultry litter has an average pH of 8.0 – 9.0, this is considered a high pH or alkaline. The pH can influence ammonia volatilization. Ammonia release from litter is minimum when litter pH is below 7; emission exceeds when pH is 8 and above. At litter pH lower than 4.6, the economically devastating bacteria like E.coli, Salmonella, Clostridium, and Campylobacter do not grow.
GENERAL EFFECT OF AMMONIA GAS: Ammonia gas has a characteristic pungent odour. At high concentrations, it is irritating to mucous membranes of the respiratory tract and the conjunctivae and corneas of the eyes. Damage to the mucous membranes of the respiratory system increases the susceptibility of birds to bacterial respiratory infection, especially E. coli infection. High levels also have a negative impact on overall livability, weight gain, feed conversion, condemnation rate at processing and the immune system of the birds.
DAMAGE TO THE RESPIRATORY SYSTEM: The effect of ammonia gas on the mucosal surface of the trachea ranges from paralysis of cilia to deciliation (loss of cilia) of epithelial cells, to injury (necrosis) of the mucosal epithelium itself. Attenuation of the mucosal epithelium, with loss of cilia and increased numbers of goblet cells, are common lesions of aerial ammonia toxicity seen in the tracheas of affected birds.
DAMAGE TO THE EYES: Atmospheric ammonia at high concentrations causes conjunctivitis (inflammation of conjunctivae) and damages the cornea of the eyes. As in the respiratory system, the severity of the damage depends on the concentration of ammonia in the environment and duration of exposure. Swelling and reddening of the eyelids, reddening of the conjunctive and nictitating membrane (third eyelid), and partial or complete closure of the eyes are common clinical signs. In severe cases, the eyelids are often closed shut. Eyes can become almond shaped after longterm exposure to high ammonia levels because of scarring and retraction of the eyelids. Conjunctivitis caused by ammonia also increases the risk and severity of swollen head syndrome in respiratory viral infections.
LESIONS IN THE CORNEA: The term “ammonia burn” is used by some to refer to ammonia-induced corneal erosion, but this term is inaccurate, as ammonia does not directly injure the corneal epithelium. Damage to the basement membrane on which the epithelium rests is responsible for detachment of the epithelial layer, which is the characteristic eye lesion that results from excess ammonia exposure. The lesion is an almost circular, an grey-white, opaque, rough-looking area in the centre of the cornea.
Various approaches have been adopted to reduce NH3 production with the basic aim of either to inhibit uric acid breakdown or to bind the released NH3.
i) Better management- the easy way out Proper maintenance of liner in good condition by avoiding housing birds at high stocking densities, prevention of cake formation by regular raking and proper water management and provision of good ventilation to remove dust, odours and moisture from the air will greatly help in preventing this problem to occur.
ii) Chemical treatment of Utter – Addition of certain chemicals to litter is the common practice to obtain an immediate but time-bound effect. Paraformaldehyde, a mixture of polyoxymethylene glycols, disintegrate slowly and release formaldehyde gas which will chemically combine with atmospheric ammonia to produce no odorous, nontoxic and white product called hexamethylenetetramine and water (Walker, 1964).
The antimicrobial action f form¬aldehyde has the added advantage of reducing microbial populations both in air and in the litter. Various workers (Seltzer et al; 1969 and Veloso et al; 1974) have added this compound in flake form to litter and observed satisfactory effect up to about 3 weeks at 3% (w/w) inclusion. Hydrated lime and superphosphate were found to be effective at levels of about 5% (w/w) and Ikg/m 2, respectively (Cotterill and Winter, 1953 and Reece et al; 1979). These compounds are widely used owing to their cheap cost and value as fertilizer. Phosphoric acid, when sprayed on litter @ 0.4 kg/m 3 greatly reduced litter pH and inhibited NH3 production up to 3 weeks (Reeceetal; 1979).
iii) Dietary treatment
The possible role of dietary zeolites in controlling NH3 production, in addition to their proven toxin adsorption capability and perfor¬mance stimulating effect, need to be studied further in view of the scanty information, avail¬able (Mumpton and Fishman. 1977). Similarly, bentonites addition to the diet may also be of some use. Dietary addition of antibiotics like Zinc bacitracin or Thiopeptin @100 mg/kg also was found to depress NH3 production from the litter (Kitai and Arakawa, 1979). the urease inhibiting effect of hydroxamic acid, observed in large animals (Streeteretal; 1969)offers another great scope for its practical use in poultry rations.
Extract of Yucca schidigera, a plant com¬monly seen in Mexico and US is presently used widely in manufacturing commercial preparations because of its known depressing effect on NH3 production from the litter (Rowland et al; 1976 and Johnston et al; 1981). Others like Sorbic acid, adipic acid, gentian violet, calcium propionate, Copper Sulphate, Ferrous Sulphate, formic acid and benzoic acid, significantly reduced dietary microbial counts (Gwara et al; 1989; Kaczmarek et al; 1989; Brake et al; 1990 and Ramakrishna et al; 1992) and therefore, their addition to diet may have some depressing effect on litter NH3 production by lowering litter microbial counts.
iv) Microbial treatment of litter
Inoculation of the litter with certain genera of microorganisms that reduce the production of mycotoxins like Scopulariopsis (Forgolcs and Carils, 1962) may be extended for minimizing the flora that takes part in NH3 production.
Productive performance and disease resis¬tance of chicken are drastically affected by high atmospheric NH3 concentrations. This problem may be alleviated by treating diet or litter with certain compounds that hinder the production of NH3 either directly or indirectly.