37. House temperature should be carefully monitored and controlled. This is influenced by factors such as efficiency of insulation, ventilation and the presence of supplementary heating and/or fans; all of these may be easily regulated in a modern broiler breeder house. The guidance provided by the primary breeding companies includes optimum temperature ranges for the various growth stages. The stockperson needs to monitor the behaviour of the birds in order to ensure that temperatures are appropriate and make adjustments as necessary.
38. Chicks should be placed in the brooding area when they arrive in the house and their behaviour monitored carefully. Young chicks are particularly susceptible to extremes of temperature and the even distribution of the chicks in the house will indicate when they are comfortable.
39. Older birds are less susceptible to variations in temperature. Nonetheless, extremes should be avoided by use of supplementary heaters or cooling fans. Birds on restricted feed are more susceptible to low temperatures but less so to high temperatures. Thus, if the temperature is allowed to fall there may be a need to increase feed.
40. We observed no welfare problems directly related to temperature control and were pleased to note that the industry is well aware of the adverse effects of temperature extremes on the welfare of the birds.
41. Effective ventilation is essential to control temperature and humidity and so reduce the likelihood of heat stress, as well as being the major determinant of both air and litter quality. It follows that the design of the ventilation systems has a major influence on bird welfare. The systems should provide air containing sufficient oxygen to allow normal growth and development; and should also maintain an air-flow sufficient to remove excess ammonia, carbon monoxide, carbon dioxide, moisture, dust and heat. In hot weather, the system should have capacity to prevent temperature levels rising significantly above the ambient. A fast air speed at bird level can be used to moderate the effects of high temperature. In cold weather, the system must deliver sufficient air to the birds without allowing them to become chilled.
42. We found no evidence of serious heat stress during our visits to broiler breeder houses. This might have been expected as stocking densities are at levels that limit the build up of heat and humidity. Furthermore, the controlled levels of feed reduce the production of metabolic heat. Birds experience heat stress when they are in a hot environment and are unable to prevent their body temperature from rising to unacceptable levels. Panting is the most important method of losing heat and its efficiency is reduced significantly if humidity levels are high. Producers must remain vigilant, particularly during periods of high external temperature.
43. At times of extremely high temperature, management should adopt techniques which minimise the risk of poor welfare.
44. When ambient temperatures rise above the birds' comfort zone', as indicated by periods of continuous panting, immediate, effective action must be taken.
45. Minimum ventilation rates should be sufficient to ensure air quality meets the birds' needs for oxygen, and controls ammonia, carbon monoxide, carbon dioxide and dust to levels that are not harmful.
46. Those keeping broiler breeders should apply the advice given in the MAFF publication Heat Stress in Poultry - Solving the Problem (PB 1315).