Poultry housing for bird welfare and higher productivity
Present day poultry industry utilizes hybrid broiler and layer strains with the objective of receiving maximum meat yield and eggs per bird respectively under intensive system of rearing. The technological advances in the housing systems are aimed only to reduce labour and housing cost per hen by making higher density environments in the multiple tier cages. After the publication of the book Animal Machines (Harrison, 1964) started criticisms over intensive housing systems and such criticisms gaining momentum in the recent past. While considering the bird’s welfare, the productivity of the birds over investment also to be kept in mind. Hence poultry housing should satisfy both the bird’s welfare and economics of the poultry farm.
Does Management differ from Husbandry?
Olaf Swarbrick, FRCVS, who cared about 12.5 per cent of the National egg laying flock of United Kingdom during 1991 explained that the term 'management' is often incorrectly used and should be confined to the decisions taken and the overall supervision of the enterprise provided. It must be carefully differentiated from 'husbandry', which is the day – to – day work undertaken with the livestock by the stockmen and women. This differentiation is important, because often management is used indiscriminately to include both. They are quite different functions, although on small units are often undertaken by the same people. He also indicated that husbandry, welfare, economics and costs are closely independent and cannot be separated.
Behavioral changes in the birds
Poultry farming was initially started with free-range and various loose housing methods to protect their welfare. Then the method of rearing was changed to cages during 1955. Since then the type and the density of birds per unit floor space were changed year by year. When the flock size and density of the birds increased, the behavioral problems in the birds are also increased. Broodiness of the hens was reduced by the genetic selection. Flightiness became a severe problem in cages containing larger group sizes (Hansen, 1976). Cannibalism and feather pecking, in the absence of beak trimming, were found to be major problems in many stocks in floor-pen flocks (Dun, 1992) and in well-lit cage houses (Craig and Lee, 1990). Absence of nest building materials also makes the birds frustrated and showing stereotyped pacing prior to oviposition (Mills et al., 1985).
Code of practice for the welfare of poultry
Several developed countries have intended the code of recommendations for the welfare of poultry to encourage all those responsible for looking after birds to adopt the highest standards of husbandry. The United Kingdom Farm Animal Welfare Council stated that husbandry systems should provide freedom from: 1) hunger and thirst, 2) thermal and physical discomfort, 3) pain, injury and disease, 4) fear and distress and 5) insufficient space or facilities in which to exercise most normal patterns of behavior.
Implementation of welfare code
Welfare is usually seen as the external environment around the birds, many aspects of which can be objectively and easily assessed and measured. It is the internal well being of the hens, which is likely to be far more important in order to fulfill its biological and psychological needs. Although the five freedoms mentioned under animal welfare are desirable, they are not likely to be entirely achievable. Similarly providing stress-free environment through out the life period of the hen also questionable that the stressors will eventually challenge all hens, because of unanticipated or uncontrollable events. An ‘optimal’ level of stress at least early in life may be advantageous; because animals are then able to cope better when environmental stressors occur later in life.
The extent of compromising the birds’ welfare with higher productivity may be attributed to a number of factors like culture, economics, religious and philosophical beliefs, scientific knowledge and aesthetics (Craig and Swanson, 1994). When balancing the socio-economic condition of our Nation and the welfare of birds we can mainly concentrate on suitable poultry house design, sufficient floor space in cages and cage design and optimal environmental conditions around the bird.
Poultry house design
The open sided poultry houses are constructed with its length extending from east-west direction to minimize the entry of direct sunlight, to exploit the direction of the prevailing winds and to minimize solar heat radiation.
The width of the open sided deep litter broiler house in the tropics preferably around 30 feet (10 m). The width can go up to 40 feet in case of tunnel ventilation system, environmentally controlled houses and elevated platform cage houses.
The floor of the poultry house must be cement concrete and should be elevated at least 30cm from the outside ground level to prevent seepage of rain water entering into the poultry house. In case of cage rearing, elevated platform cages are preferable for proper ventilation.
The height of the sidewall will be 30 cm and the remaining height up to eaves will be covered with chain link mesh as protection against theft and predators from outside. In case of cage system of rearing, sidewall is not needed. Insulating adjustable roll-down curtains in the sidewalls might be helpful during brooding period, rainy and windy seasons. Solid construction of end walls is mostly referred. These walls may be fitted with either exhaust fan or pad coolers, or tunnel ventilation system, depending upon the cooling system followed.
` The poultry house should have elevated ceiling to keep heat radiation away from birds. The height of roof should be 2.5 to 3.0 m (8 to 10 feet) at eaves and 4 to 5 m (13.5 to 16 feet) at ridge is preferable in tropical areas.
To protect birds from exposure to direct sunlight and splashing of rainwater into the poultry house, the roof at both eaves will be extended as overhangs for about 3 to 5 feet on either side. As a thumb rule, the ideal width of the overhang will be half the height of open space at eaves.
Type of roof material
Type of roof material also plays a significant role on well being and performance of the birds. Sivakumar et al. (2004) studied the effect of different roofing materials on microclimatic elements and reported that birds housed in asbestos roofed cage houses exerted significantly lower (P<0.01) mortality rate and better feed efficiency than those housed in asbestos roofed deep litter; tile roofed cage; and tile roofed deep litter houses.
Sufficient cage floor space and cage design
The floor space of cage birds should provide adequate freedom to stand normally, turn around and stretch their wings. Adams and Craig (1985) indicated that productivity decreased, on an individual bird basis, and mortality increased as density increased. If more birds are housed than the holding capacity, the birds in the social order will be forced to yield room to more senior ones, accounting for higher than normal depletion. In overcrowded houses, losses in terms of excessive culling or mortality are therefore common. European Union welfare directives imply a minimum of at least 600 cm 2 per bird against the floor space of 450 cm 2 per bird adopted in India. It indicates that the floor space allowance per bird under cage system of rearing can be increased by 30 per cent to that of present floor space given in commercial layer farms. Increasing cage floor space from 400 cm 2 to 600 cm 2 reduced the percentage of cracked eggs from 1.67 to 1.24 in cage layer houses (Hernandez Vargas et al., 1994).
For improving the welfare of the cage birds several manufacturers in western countries introduced different cage designs as enriched cages or welfare cages allowing sufficient floor space per bird (600 cm 2 per bird) plus extra room for a nesting box (156 cm 2 per bird) and a dust bath (120 to 156 cm 2 per bird). These additional provisions will necessarily increase the cost of cages and labour. By considering the fact of welfare of the birds and cost of investment per bird in India, we may increase the floor space by 10 per cent to that of present cage floor space allowance i.e. to 500 cm 2 per bird (Leghorn type layers). Providing additional facilities in the cages like nesting box, perches and dust bath are preferable but not compulsory under our present day socio-economic conditions to get higher productivity. However, the openings of the cages should be sufficient enough to prevent the injuries when the birds are taken out or placed inside the cage.
Environmental conditions around the birds
To compensate the loss of freedom in intensively reared birds, comfortable living environment is necessary. Temperature of the bird’s environment is one of the most important factors for its productivity. Birds are homeotherms (warm-blooded), i.e. they maintain a constant body temperature regardless of the environmental temperature. The comfortable environmental temperature for adult birds ranges in between 65 0 and 75 0 F (18 0 and 24 0 C). Variations in environmental temperature beyond this range will affect the productivity of the birds. Hence special heating / cooling systems are installed in the poultry houses to protect the birds during cold or hot periods.
Oxygen is the life-sustaining element and should be supplied continuously to meet out the demands of every cells of the body. When adequate ventilation is provided inside the poultry house, it satisfies the oxygen need. At rest, a normal hen consumes about 1 cubic foot of air in one hour. It increases when the bird is active. Carbon dioxide is the main gas exhaled from the lungs. Since the carbon dioxide is relatively heavier than other gases, it remains at bird level on the floor if ventilation is inadequate and affects the percentage of oxygen. Fresh air normally holds about 20 per cent oxygen. An atmosphere containing less than 19 per cent oxygen will affect the oxygen concentration in the hemoglobin, in the blood, on which depends the entire health of the body.
Ammonia is another gas produced in warm and humid houses. Since it is lighter in nature, it rises and if easy exits are not available, accumulates near the ceiling room where it can be pushed down again by fans. When ammonia reaches a level of 15 to 20 ppm it will affect the growth and production performance of the birds.
Adequate air movement in the house, effective ventilation and dry litter are the only measures to help avoid harmful influences from polluted air. Many poultry farmers reduce ventilation during cold weather to reduce fuel costs but it is not advisable. Clean and fresh air is just as important to growing birds as fresh feed and water. To achieve proper oxygen level inside the poultry house and to eliminate carbon dioxide, ammonia and other toxic gases, the speed of entry of fresh air and expulsion of exhaled foul air from the house should not be less than 0.5 cubic foot per bird per minute.Conclusion
The protein demand for Indian population is manifold to that of recommendations. The cheapest protein rich food source is poultry egg and meat. Due to the implementation of globalization, the poultry industry faces the competition from different angles of world compels them to produce meat and egg at a competitive cost. However, the welfare of the birds cannot be ignored at the cost of economical production. By providing 10 per cent extra cage floor space to birds, suitable cage design and providing optimal environmental conditions around birds will balance the welfare of the birds and higher productivity to some extent under Indian socio-economic conditions.
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|Source : IPSACON-2005|