Farm management during the early brooding stage in the life of the chick or poult will determine whether they will reach their full potential. Every hour that a chick’s or poult’s environment is less than optimum reduces growth rate and increases feed conversion ratio and that loss recovered by the end of the growout (Dozier and Donald, 2001). Costs to both the grower and the integrator will be high if a proper brooding environment does not ensure that birds get off to a good, healthy start. The focus of this article will be on how to best meet the needs of the broiler chick and turkey poult brooding.


Brooding the Broiler Chick

The objective in brooding chicks is to provide growing birds a comfortable and healthy environment, efficiently and economically (Vest, 1997). Temperature (particularly of the floor), ventilation rates, humidity, litter conditions, dust and gas levels are all environmental critical control points that growers must monitor and manage. Failure to properly manage these environmental critical control points during the brooding period will likely result in lower economic returns.

The body temperature of a day-old chick is about 3° F below that of an adult, but by five days of age body temperature has reached 106° F, the same as the adult (Vest, 1997). Newly hatched chicks have little or no ability to regulate their own body temperature and depend on the grower to provide an ideal growing environment (Dozier and Donald, 2001). Yet the ability of chicks to regulate their body temperature has a direct impact on the birds ability to grow efficiently. This means that exposing chicks to temperatures too high or too low will result in energy and nutrients being expended to cool the bird by panting or to warm the bird
by heat production (Lacy, 2002). However, ever increasing fuel costs usually mean that over heating of chicks is a rare occurrence.

When a newly hatched chick is placed in a cool environment, its internal body temperature begins to drift downward toward the environmental temperature and may reduce the growth efficiency of the bird. Keep in mind, that in broiler houses, floor temperature is often 5 to 15° F below air temperature (Lacy, 1997). The temperature of the broiler house floor during brooding is more important than air temperature, since chicks are in direct contact with the floor. Even fairly brief exposure to cool floors can adversely affect chicks.

In one research experiment, 175 newly hatched chicks were placed in either a constant temperature of 95° F or were exposed to a temperature of 65° F for two hours and then at a constant 95° F. After four days the internal temperature of chicks subjected to that brief cold exposure was only 100.5° F, versus 102° F for the control group reared at a constant 95° F (Dozier and Donald, 2001).

Normal development of the digestive, circulatory, nervous and immune systems of the chick depends on the bird using the nutrients and antibodies provided by the yolk sac to ready these systems to begin getting nutrients from the feed (Dozier and Donald, 2001). If chicks are chilled, nutrients that might have been used for body development are used to maintain body heat. Chilled chicks also tend to huddle together, and most do not seek out feed or water, so a number of birds may die. The performance of the chicks that survive chilling is likely to be limited due suppressed digestive or immune system functions. Periods of extended cold stress force the chick to begin breaking down the carbohydrates and fats in its own body tissues to maintain body heat, since it is unable to acquire enough from the feed alone.

Deaton et al. (1996) brooded chicks at starting temperatures of 95°, 90°, 85°, or 80° F, then decreased brooding temperatures by 5° F each week for three weeks. After three weeks temperatures were held constant at 70° F. At three weeks of age body weight and feed conversion were better for the chicks brooded at the warmer temperatures (Table 1). Since low environmental temperatures cause increased feed intake and higher oxygen demand, chilled birds are in an ideal situation to develop ascites (Table 2) (Lacy, 1997). University studies have shown increases in ascites as high as 11% in broilers raised in too-cool brooding environments (Dozier and Donald, 2001).


Table 1. The effect of brooding temperature on body weight and feed conversion of broiler males at 3 weeks of age¹.

Temperature ºF			Body Weight (lbs)	Feed Conversion
Week 1	Week 2	Week 3
95	90	85	1.76	1.35
90	85	80	1.75	1.37
85	80	75	1.74	1.39
80	75	70	1.66	1.42

¹ Adapted from Lacy (1997)


Table 2. The effect of brooding temperature on mortality of broiler males at 6 weeks of age¹.

Temperature ºF			Total Mortality (%)	Ascites Mortality (%)
Week 1	Week 2	Week 3
95	90	85	2.29	0.83
90	85	80	3.12	0.83
85	80	75	1.67	0.62
80	75	70	4.79	2.50

¹ Adapted from Lacy (1997)


The proper temperature for brooding broiler chicks will depend on the system being used. However, it is important to realize that supplemental heat will be required even in the summer and especially at night (Dozier and Donald, 2001). Brooding systems have been classified various ways. Dozier and Donald (2001) suggest that forced air furnaces and brooders are the two basic methods of providing heat for chicks, while Lacy (2002) mentions three methods of warming chicks ( warm room brooding, hover (or pancake) brooding and radiant brooding). Lacy (2002) lists recommended temperatures for each brooding method (Table 3).


Table 3. Recommended Temperatures for Broilers

Weeks of Age	Brooder Type
	Warm Room ºF	Hover ºF	Radiant ºF
1	88	90	85-88
2	83	85	82-85
3	78	80	77-80
4	73-76	75-78	73-76
5	70-73	70-73	70-73
6	65-70	65-70	65-70

Adapted from Lacy (2002)


Furnace heat (or warm room brooding) is more difficult to manage than pancake or radiant brooders for two primary reasons. First, furnaces produce warmth by producing heated air. This means that the floor must be warmed from hot air, which can require a long period since hot air rises, and temperature stratification can develop with hot air at the ceiling and cold air at the floor. Mixing fans near the ceiling work well to break up stratification and should be utilized to increase floor temperature and decrease gas usage (Dozier and Donald, 2001). Second, furnace heat does not allow chicks to select a comfort zone. The entire room is heated and chicks must grow at the selected temperature. This means that there is little room for error with furnace heat; the temperature maintained must be exactly what chicks need, since they can not find a warmer or cooler area (Lacy, 2002).

Both pancake and radiant brooders allow chicks to move toward or away from the heat source to seek a comfortable temperature (Lacy, 2002). Most of the heat from these brooders is in the form of infrared light, which heats objects instead of heating the air (Dozier and Donald, 2001). Floor temperatures under the brooder will be higher than the surrounding air temperature, so that heat is delivered where it is most needed ... at chick level (Dozier and Donald, 2001). In recent years radiant brooders have become popular, since they have been shown to reduce fuel costs by 15 to 30% as compared to pancake brooders and forced air furnaces (Lacy, 2002).

Although warmth is a critical need for newly hatched chicks, these young birds also require a minimum amount of ventilation during the brooding period. Ventilation is necessary to add oxygen, remove harmful gases (carbon dioxide and ammonia) and to remove moisture added by the birds. As the ventilation system operates, cool fresh oxygenated air is brought uniformly through the inlets and jetted along the ceiling toward the center of the house, mixing with hot air already in place and sending it back toward the floor. At the same time, humidity, ammonia, dust and carbon dioxide are removed from the house while the exhaust fans are in operation. Without adequate ventilation, ammonia, humidity and the lack of oxygen can reduce performance and increase mortality.

Many growers underestimate the effects of ammonia on flock performance. Ammonia levels of 25 ppm (barely detectable by the human nose) have been shown to depress growth by 4 to 8% and increase feed conversion by 3 to 6%. Just 5 ppm ammonia has been shown to irritate and injure the protective lining of the chick’s respiratory system, causing the bird to be more susceptible to respiratory disease. If growers wait until ammonia levels are high enough to be detected by odor or a sense of smell, some damage has already occurred. To minimize ammonia problems it is important to provide adequate ventilation and control moisture in the poultry house (Lacy, 2002).

Birds add moisture to the poultry house environment by respiration and by feces excretion. Since birds, like all animals, exhale warm moisture laden air, respiration increases the humidity of the inside environment, which can, if not removed, cause increases in litter moisture. Broilers consume about one and a half to two times as much water as feed, but they only retain about 20% of the water, thus the other 80% is excreted (Dozier and Donald, 2001). A broiler chick excretes about 0.06 ounces of water per hour in the first week, and about 0.11 ounces per hour in the second week (Dozier and Donald, 2001). Assuming birds are provided 23 hours of light per day, this would mean that during the first week a flock of 20,000 birds would add slightly over 1,509 gallons of water to the poultry house environment. During the second week the same flock would add about 2,767 gallons of water to the poultry house. The amount of water excreted increases with bird age and weight. This, in part, is why we must increase ventilation rates as the birds age — to compensate for the additional water being added to the litter. If litter moisture and humidity are not removed, litter moisture increases, leading to damp, caked or wet litter conditions. However, the level of humidity also appears to be critical for poultry (Vest, 1997). Results show that increased relative humidity leads to depressed feed consumption, independent of temperature (Table 4) (Vest, 1997).


Table 4. Feed consumption in grams as influenced by relative humidity in 4 week old broilers.¹

Temperature (ºF)	Relative Humidity (%)
	37	49	56	67	73	82
	Feed Consumed (grams)
90	44		14
81		56			50