2.1.2. Environmental requirements

Temperature

Hens can tolerate hot climates (25°C and over) and their productivity is barely affected in such conditions. The danger in such climates is “heatstroke” when the normal temperature increases by 5 to 10°C or more over 24 or 48 hours. In such conditions, the organism is taken unawares and cannot become acclimatized so quickly, leading to:

- Reduced feed consumption
- Increased water consumption
- Loss of productivity (growth, laying)
- Fragile eggshells (breakage)
- Increased mortality

The temperature in a poultry house is measured by placing the bulb of the thermometer at the same height as the backs of the poultry.

How to combat excess heat

There is no miracle solution, but various ways of controlling the situation can be tried:

- Distributing feed during the cool part of the day, perhaps in the evening, although in this case artificial lighting (electric or otherwise) should be provided above the feeders.

- A sufficient number of feeders and drinkers is more important than ever.

- Check that stocking density is not excessive (follow the instructions of the breed producer); if necessary reduce it by 25%.

- Water supply pipes should be buried and not placed on the ground, while water tanks must be insulated from the blazing sun by means of straw, reeds etc.

- Natural ventilation is inadequate to eliminate excess ambient heat in the buildings and supplementary electric ventilation can be very beneficial (the only drawback is energy consumption).

- Adopting high energy (using fats) and high nutritional density feed to offset the negative effects of under consumption of feed on the birds' performance.

Hygrometry

The degree of relative humidity (RH for short, measurements of water vapour in the air) should ideally be between 55 and 75%. Below that, the air is too dry and irritates the mucous membranes. Above that level, humid air, especially in the event of extreme heat, hinders the lung function of the poultry in eliminating excess calories. Moreover, in such conditions, the litter becomes wetter due to increased water consumption by the birds and lack of evaporation, resulting in increased development of coccids in the litter and fermentation within the latter.

Ventilation

Ventilation consists of renewing the ambient air by bringing oxygen to the birds, eliminating deleterious gasses (carbon anhydride, ammonia, sulphur anhydride, methane, etc) as well as dust.

Ventilation must be effective but not excessive in order to avoid draughts. Air speed should be 0.2- 0.3 m/second but may reach 1 m/second if temperature is 30°C which allows the temperature perceived by the bird to be reduced by about 3°C.

Light

In the brooder, lighting will be permanent for the first 48 hours. Subsequently, darkness must not exceed 10 hours in 24.

Laying begins earlier as the days lengthen. Conversely, it is delayed by decreasing day length. In most poultry houses in the Sahelian zone, dependence on the natural cycle of days is total and sexual maturity can only be controlled by means of rationing the feed of the pullets.

During the laying season, the period of lighting cannot be reduced as this would have a physiological effect inhibiting laying.

Readers should refer to the instructions of the breed supplier for more details on the recommended lighting programmes.

Litter

Litter must be made of absorbent materials and not be dusty, since dust irritates the birds' respiratory system, thus contributing towards the development of respiratory diseases. Materials which can be used for making litter are: wood shavings (with little sawdust), chopped straw, groundnut shells, fragments of sugar cane waste, rice husks and waste paper.

The litter must not be too thick (risk of fermentation) but adequate, 4 to 5 cm. It must be neither damp (maximum 25 to 30% water) nor dusty

In laying houses, litter must be added regularly and this may be as much as 30 to 35 cm thick at the end of the cycle.