Brian Fairchild, a poultry extension scientist at the University of Georgia, discussed temperature and chick physiology; the effect of temperature on chick growth performance; the importance of relative humidity, ventilation and light, and energy conservation.
The main goal of raising chicks is to provide a comfortable and healthy environment for growing chickens effectively and economically. Temperature, air quality, humidity and light are important considerations. Failure to provide an appropriate environment during brooding will result in growth retardation, decreased feed conversion rates, and increased disease, elimination, and mortality rates, which will reduce the profitability of the chicken industry.
Temperature and chick physiology
Maintaining the proper temperature is the key to chick brooding, especially in the first two weeks of chick life. The poor self-metabolism regulation ability of chicks is not enough to control body temperature. Therefore, chicks rely on ambient temperature to maintain optimal body temperature. If the room temperature drops, the body temperature of the chicks will also drop. Similarly, if the room temperature increases, the body temperature of the chicks will also increase.
During the brooding period, too cold or too hot will lead to slow growth of chickens, poor feed conversion rate, and increased disease susceptibility. Appropriate brooding measures must be taken to maintain body temperature, so that chickens do not need to metabolize asthma or generate heat to maintain body temperature and lose energy.
Studies have shown that chicks develop self-regulating body temperature about 12-14 days of age. Chicks are easily stressed if their body temperature drops or increases by 1 degree. Once the temperature changes, the chick will try to compensate compensatively, which means that it will have an adverse effect on growth performance. 0-day-old chicks have a body temperature of approximately 103°F (39°C), but by 5 days of age the body temperature is 106°F (41.1°C), which is the same as adult chickens.
Extreme (high or low) temperature usually causes chicks to die, but even slightly cold or hot will affect the growth performance of chicks but will not be lethal. Chicks tend to be more tolerant of high temperatures than adult chickens. Continued high temperature for a period of time will increase mortality and negatively affect growth performance.
Research shows that chicks suffering from low temperature will weaken their immune system and digestive system. Therefore, the growth performance of chicks suffering from cold stress will decrease and the disease susceptibility will increase. Cold stress chickens will only have a higher incidence of ascites, and mortality and elimination rates in processing plants will also increase.
Research chickens raised at 80°F or 90°F have better body weight gain, feed conversion rate and survival rate. The growth rate of chickens brooding below 80°F is lower than that of the high brooding temperature treatment group. The chicks raised at these temperatures cannot keep up with the weight, so the chicks that weighed less than the appropriate temperature when they reached market age. Not only do chicks raise their growth rate, but they will consume more feed to keep themselves warm, which reduces feed efficiency and increases feed costs.
Temperature and chick growth performance
One of the goals during brooding is to maintain the chicks in their comfort zone. The chicks do not need to use energy to increase or remove body heat to maintain body temperature.
When the ambient temperature of the chicken is higher or lower than the ambient temperature of the comfort zone, it takes more energy to maintain body temperature. This excess energy will eventually be provided by consuming feed. Therefore, the energy from the feed will be used to maintain body temperature instead of growth and development, which will cause the feed conversion rate to decrease. Therefore, the ambient temperature plays a major role in determining the cost of meat production or breeding hens.
Reasonable brooding includes not only maintaining the proper temperature but also the use of good management practices. The brooding temperature will vary depending on whether the heat source is a hot blast stove, a traditional brooder or a radiation brooder (Table 1). Note that the temperature in Table 1 refers to the air temperature when set to provide a floor temperature of 90°F (32°C).
In brooding, the floor temperature is very important. Studies have shown that the average floor temperature when placing chicks in the house must be 90°F (32°C). Hot air stoves need to set a higher temperature, because they must first heat the air, and then let the heated floor heat. Traditional umbrella brooders directly use about 40% of the heat to heat the floor and 60% of the heat to heat the air. Radiant brooders use about 90% of the heat for the floor and 10% for the air. Because the umbrella and radiant brooders directly use more heat for the floor, the air temperature used to obtain the ideal floor temperature is lower than the air temperature required by the hot blast stove.