Poultry housing conjures up scenes of large, enclosed buildings with birds at ultra-high densities but in Africa housing traditionally covers a much broader spectrum and is generally more bird-friendly, writes Dr T Mabbett
IRRESPECTIVE OF SIZE and design a poultry production system whether for laying, meat or breeding birds must provide the profile of basic bird requirements:
• fresh air free from in-house or outside sourced contamination
• fresh clean feed and water free from disease causing agents
• physical protection against predators
• protection from weather extremes including low temperature, high temperature with or without high humidity and direct effects of rainfall, sunlight and atmospheric air movements (wind).
• A source of heat will almost certainly be required when birds are young. Natural or artificial air movement (fan-generated) is invariably required during at least part of the year for cooling and ridding the ambient house atmosphere of contaminating odours such as ammonia from poultry faeces.
Birds have changing needs according to growth, development and season. Good producers are sufficiently flexible and adaptable and supply these needs when and where required. Poultry production means dedication with farmers providing a ‘total comfort package’ in which birds can feed, sleep grow and lay eggs in comfort, free from physiological stress, pests and disease. A crucial but generally underrated part of the ‘total poultry comfort’ package is provision of adequate space for each bird and access to perches and dust bath facilities that allow birds to follow as far as possible their natural behaviour patterns. Animal welfare requirements are satisfied and farmers reap rewards with increased production.
Always remember that happy healthy birds repay with sustainable growth and production. Chickens are still the mainstream species in African poultry production but others are mentioned where appropriate. Basic housing needs A well designed poultry house must protect birds from the weather, predators, injury and larceny and provide a stable environment where they feel comfortable during daylight and darkness. Dryness and draft free conditions are essential. In truly tropical climates, doors, windows and even walls may not be necessary but in cooler climates or tropical climates with a distinct cool season windows and doors that can be opened and closed for ventilation and insulation according to prevailing conditions are essential.
Open-sided houses widely used in Equatorial Africa should be built with a sufficiently long roof over-hang to keep out rain during the wet season. Layers require secure nesting boxes. Site poultry houses on high well-drained land to avoid any prolonged dampness or water logging of house floor or outside area. Drainage channels and ditches may be required to carry away excess rainwater and minimise any rise in humidity after rainfall. Relative humidity inside enclosed houses is exacerbated by over-stocking. Predators including birds of prey, rodents and reptiles pose significant problems for many African farmers, especially those producing near areas of forest or tree crop plantations. Only way to avoid sustained loss is to keep chickens within a totally confined area, either a purpose built poultry house or a fenced and covered run. Producers should ideally invest in a concrete floor to stop snakes gaining entry and mammalian predators from digging under the walls and floor. Windows and doors should be securely covered and protected with wire mesh.
Add-on outside runs
Birds in houses with add-on outside runs become more difficult to protect from predators and the elements. However, the extra and higher quality space in the run will offer many welfare benefits for birds, allowing them to carry out considerably greater amount of normal avian behaviour, including access to green plants with vitamins and minerals (including vitamin K ) and soil for pecking and picking up grit to aid digestion. Dust bathing for hens and water bathing for ducks provided with ponds, pools or water baths is also possible.
The downside of add-on outside runs is reduced all around safety and security for birds. Wire delineating margins of the pen should be buried a minimum 30cm deep in the soil, with the buried portion displayed outwards at a slight angle to prevent predators from digging beneath the fence. Many predators tend to dig at the base of a fence and setting fences at an angle under the ground will deter attempts at entry. If outside runs are not predator-proof then poultry must be shut in securely before darkness and let out again early in the morning just after the sun gets up. Young chicks are especially vulnerable to birds of prey including hawks and owls which can only be excluded by covering cover outside runs with mesh wire or netting.
Failing this, a mesh or grid composed of string and tied across the top of the wire will provide a sufficiently good deterrent against flying predators. Houses must be designed and built without leaving any potential for injury to birds. Any loose or projecting wire nails, or any other sharpedged objects must be eliminated from both the house and run. Dedicated custom-made perches should be the only projections present in the house that birds could conceivably perch on. Birds attempting to perch on inappropriate projections often damage themselves. Chickens need solid sound shelter but not at the expense of good air circulation or adequate light. The common use of galvanized or corrugated iron roofs in hot climates is not always a good idea because the house will heat up quickly and considerably from direct sunlight during the day. The situation is aggravated because chickens are unable to cool themselves down through evaporation from the external body surface.
Body heat is lost by birds opening their beaks and panting but this may also be a sign of heat stress. The relatively high normal body temperature of chickens means they are especially vulnerable to heat stress caused a fall off in feed consumption, lower growth and laying rates and risk of death just a few degrees above 40 ºC.
Space is the single most significant principle in poultry production because total amount available governs the number of a particular poultry type that can be kept. Space is commonly defined as bird density or space available per bird. Birds require room sufficient for normal vital movements (e.g. feeding) and exercise, as well areas dedicated to nesting and roosting. Space requirement varies according to species and breed of birds and production system. For instance, laying hens require 1.5 square feet per bird if inside and eight if outside.
Ducks whether kept inside or outside need more, at three and 15 sq ft/bird, respectively. Similarly minimum density for layers flocks is three birds/m2 and 4-5/m2 for broiler (meat) birds. Producers must meet minimum space requirements which are exactly what they say with birds obtaining complete dietary needs without having to search and forage for feed and water. Minimum space requirements can be quantified as number of birds in one square metre of floor space or space square footage required per bird.
As a general rule chickens stay comfortable at a density of up to four individuals per square metre, although space over and above this minimum means they can display more varied and higher quality behaviour which is good for bird welfare and production. Less than the minimum creates and aggravates stress and negative social behaviour. Birds are more prone to disease and cannibalism and weaker individuals suffer at feeding and perching points.
Very high densities currently used in commercial intensive production of both layers and broilers prevent normal behaviour and exercise. Animal welfare concern has provoked a substantial rethink on cage layer systems with the European Union leading to phasing out basic cage structures in favour of so-called enriched cages or colony systems, with prospect of a complete cage ban in the future. Air circulation and heat stress Continual air movement and circulation is essential for all poultry houses to replace stale air saturated with moisture, ammonia and carbon dioxide by fresh air rich in oxygen. Small poultry houses usually get by with windows or vents down one side of the house or open-sided structures in climates with no cold season. Large completely enclosed intensive production systems will require a dedicated ventilation system.
Failure to ventilate allows build up of toxic gases and a combination of high temperature and relative humidity causing heat stress, production loss and rapid onset of mortality. Heat stress is probably the single most important factor holding back production in tropical climates. Chickens can survive temperatures below freezing but because normal body temperature is relatively high (about 40ºC) the safety zone between normality and mortality around 46ºC is clearly very narrow. Danger signs as heat stress symptoms including reduced feed intake, and therefore lost production, start to kick in as the temperature creeps above 40ºC, especially with accompanying high relative humidity. Chicken houses in temperate regions should be built on a north-south orientation to absorb heat from the sun rising in the west while houses in the tropics should be built so that the length of the building is along an eastwest orientation to minimize reception of direct sunlight.
All metals including tin, corrugated iron and galvanised iron should be avoided as building materials because these excellent heat conductors aggravate high house temperatures. Producers should make best use of the outside environment. Ensure good ground plant cover around the house to cool down the whole area by transpiration (evaporation) of water through the leaves and strategically plant trees to provide shade. Ideal ground cover crops include cucurbits like pumpkin, squash and cucumber which cover the soil quickly and completely. Trees should provide shade without obstructing air flow and house ventilation. Heat stress manifests as a range of potentially serious symptoms and changes in behaviour pattern which will include:
• Steady fall in feed intake with rise in ambient house temperature.
• Rise in water intake as birds try to buffer the effects
• Progressive and increasingly measurable fall off in growth rate
• Reproduction disruption including reduced egg weight, smaller chicks and fall in concentration and quality of sperm in cockerels.
• Increasing irritability amongst birds with pecking and blood-letting leading to cannibalism especially in young flocks
Feeders and drinkers
Poultry feeders and drinkers are best located within the outside add-on run to minimise in- house humidity.
Cover the feed if necessary to protect from rain and take feeders and drinkers in for the night if rodents are present. Clean and refill drinkers daily with fresh water and recharge during the day as necessary. Ideal height is for bottom of the drinker and top lip of the feeder to be level with the back of the bird, thus ensuring minimum waste from spillage and allowing feed and water to stay clean.
Dust bathing is an important aspect of chicken behaviour and highly beneficial for health, comfort and welfare. Chickens select an area of fine, loose dry soil in which to scratch then literally ‘bathe’ in the loose soil particles which pass between the feathers.
It is completely instinctive, highly natural and carried out for good reason – it helps birds to remove external parasites which in the feathers and on the skin. Freely ranging birds have absolutely no problem in identifying a sunny warm and location where they can dust bathe, but producers will have provide equivalent facilities for chickens kept in a house with an add-on run. Basic requirement is a large shallow box filled with fine sand or dry soil with addition of wood ash from the fire provided it is completely cooled down before added.
The dust bath thus constructed should be located under a roof or be constructed with its own roof. A raised floor of solid earth or a bamboo/wood platform and a wide roof over-hang is essential in high rainfall areas. Ventilation is an extra benefit from raised bamboo platform which simultaneously keeps flood waters at bay in the wet season and keeps birds cool in the hot season. Poultry house walls can be made from a variety of readily available materials including mud reinforced with dry grass, or bamboo with windows and doors made of wooden slats. Houses may be designed as stand-alone structures or added on to other buildings as appropriate.