When it comes to bird performance and food safety, the brooding period is arguably the most critical in a chicken’s life. The moment a chick arrives on the farm, the environmental conditions present set the pattern for the remaining grow-out period. In fact, the environment in the first seven days:
- Determines the population of intestinal flora
- Influences the passage of maternal antibodies
- Affects the bird’s immune response.
- Achieving Optimal Litter Conditions
Litter condition is the main environmental factor that drives health and performance, with litter temperature topping the list. Ideally, litter temperature at chick placement should be 90-95°F. Keep in mind that achieving that temperature may require higher settings with forced-air furnaces compared to radiant tube heaters.
When determining the temperature of your litter, it’s important you record the actual litter temperature and not the air temperature. This can be done with a calibrated infrared thermometer. Of course, visual observation can also serve as a good indicator of bird comfort. Chicks and poults should be active, well spread out and eating out of the feed pans and feeder lids. Birds that huddle, congregate under the brooders, avoid brooders completely or only sit in the feed without eating are not comfortable regardless of what the sensors are recording.
The Importance of Litter Temperature
Chicks are unable to regulate their body temperature for the first 72-96 hours of life and chilling places them under a significant amount of stress and can cause them to become immunocompromised. If chilled, chicks also undergo vasoconstriction to retain heat which interferes with the passage of maternal antibodies into the chick through yolk sac absorption and results in retained yolks. The stress of chilling, combined with impaired yolk sac absorption, retards the immune response of the chick and makes a flock much more susceptible to any disease-causing agents present in the house, which may also influence the microbiological profile of the chickens in the processing plant.
Additionally, chicks that are placed on a cold floor spend more time trying to keep warm than eating or drinking. Numerous studies have shown that birds placed on floors even as little as five degrees cooler than optimal temperature gain significantly less weight than chicks placed on warm floors. Chicks hatched from young hen flocks or chicks that were chilled during delivery need a bit more heat during brooding to be comfortable. One simply needs to set the brooder temperature a few degrees higher than normal and these compromised birds will perform as well as and have 7-day weights as good as their larger counterparts. Proper floor temperature directly correlates to good 7-day bird weights. If birds do not achieve appropriate 7-day weights, they will not be able to make the performance up in the remainder of the flock.
Proper House Pre-Heating and Conditions to Monitor
House pre-heating should begin at least 48 hours prior to chick placement to ensure proper litter temperature. In houses that are not properly preheated, litter temperature can be as much as twenty degrees lower than the air temperature.
It’s also important to monitor the moisture content of litter. When damp bedding is placed in poultry houses, it serves as an evaporative cooling pad that chills chicks and is detrimental to weight gain and feed conversion, and impairs the chick’s immune system, making them more susceptible to infection.
With damp bedding, Czarick and Fairchild (2006) reported floor surface temperatures 5 to 10°F cooler than the air above. Since floor temperatures are more important to chick health than air temperatures, increased pre-heating times are necessary to properly cure the bedding and, in subsequent flocks, litter before chick placement. Preheat houses 48-96 hours prior to chick placement to dry the bedding, making sure to maintain a relative humidity of 50 to 60% by ventilating as needed. When available, use radiant-type brooders, attic inlets and circulation fans to heat and dry the bedding. In warm weather, use tunnel fans to remove any moisture on the house pad from a wash-down and to promote drying of the damp bedding.
Litter and Air Quality
Air quality at brooding is also greatly impacted by pre-heating of built-up litter. In warm weather, producers often cut their pre-heating time down to as little as 2 hours under the assumption that the only reason for pre-heating is litter temperature. In reality, pre-heating is the main way to cure the litter and prepare it for the next flock. In flocks raised on built-up litter or dirt floors, adding heat to the litter initiates a large ammonia purge. This purge needs to be completed BEFORE chick placement, which is the second reason for a 48-hour pre-heat. In houses with very deep litter, houses that have been windrowed or pulverized, or in houses with damp litter, pre-heating should begin 48-96 hours prior to chick placement in order to complete the ammonia purge prior to bird placement. The increased contact time between the warm air and the floor is what completes the litter curing. Extending the pre-heat to allow this to occur will not burn significant amounts of fuel if minimal ventilation is done properly. In fact, proper pre-heating will lower overall fuel usage. By removing ammonia and achieving floor temperatures before birds arrive, ventilation demands post-placement are reduced and floor temperature is maintained rather than lost through excess ventilation.
Since the purged ammonia from pre-heating accumulates in the house even with minimal ventilation, it should be exhausted all at once with a quick period of maximum ventilation. This should be done either immediately before application of the litter amendment or in a house not receiving an amendment, an hour or two prior to chick placement. From this point on, standard minimum ventilation for the brooding period can begin.