Having outlined the consequences of heat stress to poultry, it is appropriate to discuss what can be done to combat heat stress. Both short and long term measures that have to be done immediately to cool
down birds that are visibly suffering from heat stress. As may be expected, the subject has been of interest to researchers from all over the world. For example, in 1977, a group of researchers from the University of Ibadan compared the effects of forced ventilation, night feeding +
light, drinking or dunking in cold water and dunking in normal water once a day in the afternoons on heat stress the researchers reported that night feeding + light resulted in best egg production and egg weight.
However, forced ventilation, day feeding + light, drinking cold water and dunking in normal water also produced favourable results. In another study, the same workers found that the feeding of ascorbic acid at 100mg/kg of diet or aspirin at up to 0.2 per cent of the diets were also
effective in alleviating heat stress. The beneficial effects of ascorbic acid
feeding for counteracting the effects of heat stress on broilers, was recently confirmed.
These researches demonstrate the array of short-term measures that can be taken to combat heat stress. From a practical and economical standpoint, the use of artificial lights to stimulate nighttime feeding is perhaps the most advantageous method for combating heat stress.
The minimum temperatures, which are usually recorded in the early morning, are within the range of ideal temperatures for laying hens throughout the year. Therefore if light is available, the birds will be able
to maintain a high level of feed intake during the cool parts of the day.
However, during the hot afternoons when the risk of death from heat prostration is high, the provision of ice cooled water or spraying the birds with water from a garden hose are also practical considerations for alleviating heat stress.
The installation of electrically operated mechanical gadgets to improve
ventilation or spray water in and around the poultry houses, are extensively used in many parts of the world. The most common of these gadgets is the fan. When placed on the windward side of the house, fans tend to increase the air speed as it blows through the building. At exceptionally high temperatures, it may be better to place the fans inside the house to blow the air lengthwise of the building. In some parts of the world, circulating micro jet sprinklers are installed at the point of the roof. Such sprinklers are used to spray the roof or the ground area around the poultry house with water. This aids in cooling the house and its surroundings. The installation of foggers which emit a fine mist of water that keep the chickens wet to aid in cooling the birds have also
been utilised.
A short term measure to combat the effect of heat stress that is little known to poultry farmers is the manipulation of poultry feed formulas to provide feeds with lower energy content but adequately fortified with other essential nutrients. This practice is based on the principle that the
amount of feed consumed by a bird depends on the energy requirement.
For the poultry man who has control over his feed formula, it is recommended that during the hotter months of the year, feeds should be formulated to contain lower than usual energy levels but optimally
fortified with other essential nutrients. Such diets should stimulate an increase in feed intake and consequently an increase in egg production for layers or growth rate for broilers. Related to this is the use of feed ingredients that contain fat. Where fats are economically available, they
should be used as the preferred energy source for feed formulation because they are known to produce less specific heat than other sources of energy.
Whatever methods are used for combating heat stress must be weighed against the economics of such a practice. The farmer should be free to try any methods accessible to him and select the most economical management practice in his situation.
Good housing design and construction is the most important long-term measure for combating heat stress. Nigeria is fortunate to be in a geographical region in which good poultry housing can be constructed at minimum costs. A good poultry house must provide the following
necessities: protection from rain, sun, and pest, adequate ventilation, minimise ammonia build up and reduction in humidity. The design that best satisfies these requirements in most of the tropical world is an open sided house with a suitable roofing material. A house constructed with about two-thirds of its sidewalls open but screed with chicken wire mesh and less than 11m in width in most cases will have adequate natural
ventilation for most of the year. Adequate ventilation is the most important factor for the control of ammonia build up, humidity and poultry house temperatures. The ideal poultry house should have an East-West orientation to prevent sunrays from entering the house and should be located on a well-drained site selected to take advantage of topographical features that favour free air movement in and out of the
open-sided poultry houses. Other construction details of the ideal poultry house include the selection of economically suitable roofing materials that will produce a cooling effect in the house and floors and sidewalls that can easily be cleaned and disinfected. The use of gable roofing with ridges is increasingly being used as further means of enhancing adequate ventilation in poultry houses. The presence of trees around the houses can result in shades that will produce a cooling effect in the house environment.
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