India ranks third in egg production and 4th in meat production in the world. Egg and meat are the cheapest sources of protein in human food. Demand for egg and meat is increasing compared with other protein foods. Land requirement is less for poultry farming than other agricultural and animal husbandry activities for producing protein resources.
The poultry industry is facing environmental issues because of the accumulation of wastes. The continued productivity, profitability and sustainability will depend on the management practices to mitigate environmental consequences.
Waste is described as any solid, liquid, or contained gaseous material that is being discarded by disposal, recycling, burning or incineration.
Types of waste
The poultry industry produces large amounts of waste that include both solid and liquid waste. The solid waste consists of excreta (manure), feathers, bedding materials, feed, hatchery waste (empty shells, dead embryos, infertile eggs and late hatchlings), shells, sludge, abattoir waste (offals, blood, feathers and condemned carcasses) and dead birds. These poultry wastes provide organic and inorganic nutrients if appropriately managed, otherwise environmental and health hazards.
The quantity of poultry litter produced in a broiler unit depends on,
- The litter (i.e., bedding material) management – type and amount of bedding materials
- Number of flocks reared, collection frequency, stocking density and ventilation
- Feed types and rate of feeding, feed intake and its digestibility.
Three common practices adopted for litter
management in broiler units are,
- Single-use litter
- Partial re-use
- Multi-use litter.
The single-use litter involves the total clean-out of the house after each flock and replacement of the bedding material.
Partial re-use involves the removal of litter from the brooding section for spreading on the grower section of the house. New bedding material is then spread on the brooding section. The partially spent litter is often composted for a few days to elevate its temperature to kill pathogens. Some of the spent litter may be removed after each batch, and after 2 to 5 batches the house is totally cleaned out.
In the multi-use litter, only caked material is removed (Sistani et al., 2003) and the house is disinfected. The litter in the brooding section is either left untouched or covered with 25 to 50 mm of fresh bedding material. The multi-flock litter
may increase the incidence of pathogenic microbes and parasites, and produces a spent a litter with a much higher concentration of nutrients.
Types of poultry manure:
There are different types of poultry manure such as deep litter manure, broiler manure, cage manure and high rise manure.
Deep litter poultry manure: This refers to the manure produced by layers during the laying period. Deep litter for laying hens usually consists of peanut hulls, rice husk or wood shavings in a layer of 10-15 cm deep. During production, the accumulating manure gets mixed with the litter. When excreta are added, the litter becomes moist but remains aerobic. Aerobic fermentation occurs with the production of heat and loss of CO2 and ammonia (Simpson, 1986).
In this system, the poultry birds are kept in large pens up to 250 birds each, on a floor covered with litters like straw, sawdust or leave up to a depth of 8-12 inches. Deep litter is the accumulation of the material used for litter with poultry manure until it reaches a depth of 8 to 12 inches. Suitable dry organic materials like sawdust, leaves, dry grasses, groundnut shells, broken up maize stalks and cobs, bark of trees in sufficient quantity to give a depth of about 6 inches in pen should be used. The droppings of the birds gradually combine with the materials used to build up the litter.
Broiler house manure: This manure is similar to deep litter poultry manure, but the litter is changed more frequently. There is less ammonia loss because of restricted decomposition. This results in manure richer in Nitrogen than deep litter manure.
Cage manure: This manure contains 60-70% moisture since it is not mixed with litter materials. Litter is not used when birds are used in cages or slots. An enormous loss of ammonia occurs in this manure if it is not used the earliest Two types of poultry cages viz., pyramid and stack type cages are in use. These are available in different standard sizes to meet the specific poultry producer’s needs. The pyramid-style layer cages come in 2, 3, 4 or 5 tier models, each model with a choice of automation features. These include automated feed delivery, automated egg-gathering and automated manure removal. In the laying systems, each cage contains 1-25 birds and is suspended above a pit (Overcash et al., 1983).
Deep pit or high-rise manure: The deep pit solid manure system, or high-rise building, has a concrete floor and masonry or concrete sidewalls and is typically constructed 2-6 feet below the ground. Pens or cages are then built on slotted flooring 8 feet or more above the pit floor. Because the pit is often built below ground level, care must be taken to secure that surface and groundwater are not contaminated. Foundation drains and external grading to direct surface water away help to keep manure dry so that natural composting might occur. High rates of air movement from mechanical fans located in the pit helps to keep the manure relatively dry. A benefit of the deep pit system is that manure can be stored for several months before removal.
Nutrient content of different types of poultry manure: Refer slide no. 11