Dead birds dying or destroyed on the farm can become an important source of diseases by serving as a direct source of germs and attracting insects, pests, and wild animals that carry diseases. With proper mortality management and effective bio-security programmes, many of these problems would be alleviated and production would hence be improved.
By Dr. Salah H. Esmail, Cairo, Egypt
Carcass disposal is one of the major daily problems facing poultry meat and egg production facilities, posing a never-ending task as birds succumb to congenital defects, diseases, accidents, equipment failures, and natural disasters. On-farm death losses can result in considerable volume of carcasses by the end of a growing cycle. For example, a flock of 50,000 broilers grown to 49 days of age and averaging 0.1% daily mortality (4.9% total mortality) will produce approximately 2.4 tons of carcasses. This, in fact, represents a tremendous volume of organic matter that requires environmentally and biologically safe disposal or use throughout the course of normal production cycle.
In most parts of the world, carcass disposal has received considerable attention as part of waste recycling and management programmes in association with environmental issues, and effective disposal strategies have thus been adopted using every available and suitable disposal options to the fullest extent possible. This, however, is not the case with respect to other parts of the world including Egypt, Yemen, Libya, Jordan, and some countries of the Arabian Gulf. In Egypt, for example, dead birds were until recently disposed in the Nile river, water streams and in agricultural lands, thereby presenting major sources of infection and outbreak of diseases. Only in 2006, when the avian flu has hit the country so hard, bio-security programmes have then been launched with the aim of addressing the problem through control of the factors that contribute thereto, including faulty disposal of dead birds. In this context, the Egyptian government has made arrangements with the US Department of Agriculture to invite extension agents having experience in this particular field of poultry management. Regular workshops have thus been conducted in various parts of the country, through which farmers have acquired newer knowledge and recent advances in health, environment, and bio-security issues.
The following is an overview of the methods that have been proposed for disposal of dead birds. The choice of the method to be adopted depends largely on factors such as farm economics, magnitude of mortality (routine or catastrophic), and the need to have such birds recycled and used in animal nutrition, soil fertilization, or other purposes. In many cases, however, there might be a need for adopting more than one method at one time in order to better arrest the bird disposal problem.
Composting is a controlled, natural process in which beneficial micro-organisms reduce and transform organic wastes into a useful end-product called compost. Composting provides an economically and biologically safe means of converting carcasses resulting from daily mortality into an odourless humus-like material useful as soil fertilizing agent. Studies have indicated that the use of the compost in fertilizing gardens and nurseries has resulted in an improvement of 40% in crop production.
In this method, carcasses are layered on a daily basis into the bin with other components needed to promote bacterial action and growth (Table 1). As the bacterial action progresses, compost temperature increases rapidly above 54 OC within 5-10 days, which facilitates decomposition and kills pathogens, weeds, fly larvae, etc. Once the primary bin temperature begins to decrease 14-21 days later, the material should then be moved to the second stage area for aeration and mixing.
The primary composting bins may be placed either inside or outside the poultry house. In their simplest form, the bins may each be made of wooden material at about 1.2 x 1.2 x 1.2 meters. An average 20,000 - bird house requires 4-5 compost bins to handle normal bird mortality during a typical grow-out period.
2 Disposal pit
The disposal pit is, in its simplest form, a shored-up hole dug in the ground with a small diameter opening at the top through which carcasses are dropped into the hole, providing an environment for both aerobic and anaerobic micro-organisms to decompose organic materials. In the past, this type of structure was adequate for small producers with a limited amount of daily mortality. Today, with larger birds and flock sizes, poultry producers are using concrete or timber-lined pits to assure proper performance and useful life of the structure.
In all cases, a typical pit must meet the following requirements.
- Must be located at least 35 meters from any existing or proposed well, water supply line, or seasonal high water level of any surface water source.
- Maximum depth of 2.5 meters below the land surface, with maximum width of 1.5 meters.
- Minimum of 30 cm above seasonal high ground water elevation.
- Must be duly sealed to prevent the entry of rodents, insects, and the emission of odours.
The cost of disposal pits varies widely depending on the material used and the size of pit. The useful life of the pit also varies depending on soil conditions, number of birds loaded therein, and other management factors, but 1 to 4 years is common.
Incineration is often the chosen method of disposal in poorly drained areas where pits are not acceptable or where rocky soil makes digging expensive. Recognized as one of the most biologically safe methods of disposal, incineration curtails the spread of disease and does not create water pollution problems. The comparatively small amount of waste by-product (ash) does not attract insects or scavengers and can be disposed of easily.
Homemade incinerators constructed from drums or barrels are commonly used in small private farms worldwide. These types, however, are unsatisfactory because they fail to meet temperature and air emission requirements that would support complete combustion under environmental compliance regulations for carcass incineration.
Alliteratively, commercial units are available with oil or gas burners and are usually equipped with automatic timers to ensure proper burn. Smoke discharge stacks for such equipment may also be fitted with after-burning devices that recycle fumes to complete gas combustion and diminish odours. With this type of incinerators, the average poultry grower will spend approximately $ 7.7 to incinerate 100 kg of carcasses, based on a propane cost g $ 0.16/ litre.
The incineration costs may, however, vary depending on the amount of carcass fat which, in turn, depends on age and type of birds and acts as an additional source of fuel required for incineration and hence improves efficiency (table 2). Efficiency may also vary with the same type of birds at the same age, depending on the design of incinerators being adopted, and could be doubled with the newer designs.
4 Lactic acid fermentation
Lactic acid fermentation is an anaerobic process that takes place in an air-tight tank where lactic acid bacteria transform sugars into lactic acid (Figure 1). The production of lactic acid creates acidification, which decreases the pH of the carcass material. Under optimal conditions, fermentation reduces the pH from 6.5 to 4.5 within 48 hours. This decrease in pH preserves the nutrients and permits the carcasses to be stored for several months before rendering or use for other purposes.
When running the fermentation process, carcasses are ground into small pieces of 2.5 cm in diameter or less, which could then absorb lactic acid better than do the whole carcasses and hence facilitates fermentation. A fermentable carbohydrate source such as sucrose, molasses, whey, or ground corn is then added to the ground carcasses at ratio of 1: 5 by weight. Also, an additional source of lactobacillus acidophilus, although naturally present in the intestines of poultry, should be provided in the fermentation medium to aid production of lactic acid.
The use of lactic acid fermentation to store carcasses facilitates transportation to the rendering facilities. Renderers significantly accept the material produced by lactic acid fermentation, and may pick it up at only 10% of the cost of transporting fresh carcasses. Other potential advantages include the use of fermented carcasses in animal feeding. For example, up to 20% of fermented carcasses could be added to growing-finishing pig's diets without adverse effects on feed intake or feed - to - gain ratio. In this case, however, heat treatment of this material should be considered in order to avoid possible transmission of pathogens to the animals.
- Methods, strategies and practical applications presented in this article offer a number of acceptable ways to dispose poultry mortality through composting, burial, incineration, and/or fermentation.
- The actual decision on which method is best for normal mortality should be based primarily on economics, resource factors, individual farm circumstances, and the restrictions that apply.
- In catastrophic cases, however, all methods that allow for the biologically and environmentally safe disposal of poultry carcasses should be considered because no single method will solve the problem completely.
References are available from the author upon request
[Source: World Poultry magazine Vol 30 nr 4, 2014]