The First 48 Hours: Maximize Immunity, Performance and Livability Dr. Linnea J. Newman, DVM Intervet, Inc.

Abstract

Good management during the first 48 to 72 hours of a broiler chick�s life is critical to maximize immunity, performance and livability. Avoidance of temperature stress, either hot or cold, is key to proper development of the thyroid and gastro-intestinal tract of the young bird. Rectal temperatures are the only objective measure of the chick�s thermoneutralitiy. Failure to maintain thermoneutrality may irreversibly hurt performance compared to the genetic potential. Proper feed and feeding programs, water management and air quality are also essential components of brooding to avoid stress. Remedial measures may reduce the impact of early stress, but it may be impossible to regain 100% of lost performance. It is essential to assess and correct early management problems to achieve full genetic performance potential and maximum immunity.

Introduction

Proper management during the first 48 to 72 hours of a broiler chick�s life is critical to maximize immunity, performance and livability. Chickens� yield breeds in particular� are still developing the immune system, the thyroid and intestinal tract at this time. Damage to these systems will irreversibly affect growth and feed conversion for the life of the flock.

Building Performance

The thyroid gland is responsible for producing thyroxine (and ultimately, T3), a hormone involved in protein synthesis, growth, development of the skeleton and nervous systems, and tolerance of stress. The intestinal tract is where feed conversion begins. Together, they help form the basis of performance that reaches the genetic potential. It is essential to protect the development of these organs through stress-free early management.

Avoiding stress through proper management is also critical because stress induces the release of immunosuppressing hormones called corticosteroids. Stress can turn very minor infections into life and performance-threatening infections. It can also encourage the growth of unwanted pathogens such as salmonella or campylobacter.

Thermoneutral Zone

The �thermoneutral zone� is the place where the temperature, airflow and humidity interact to produce a chick that is neither heat nor cold-stressed. All 3 components are significant:

Humidity

Humidity is the heat transfer agent. Sufficient humidity must be present to transfer heat to cold chicks or away from warm chicks. High humidity at the wrong temperature may increase the speed at which heat is lost from chicks in a cold environment or may cause rapid overheating in a hot environment. 50 - 65% RH is generally acceptable.

Airflow

Airflow impacts the temperature of the chick through wind chill. It is also needed to distribute temperature uniformly throughout the environment. Significant airflow is necessary in stacked chicks to remove excess heat. Too much airflow may chill chicks after placement in the barn.

Temperature

The actual environmental temperature is the single greatest determinant of chick temperature, but it is influenced by both humidity and airflow. At the hatchery and in transport, �environmental� temperature refers to air temperature. At the barn, floor temperature may have more to do with the chick�s comfort than the surrounding air!

How do I know when my chicks are �in the zone�?

The only way to know for certain is to take rectal temperatures of chicks throughout the house (at least 3 locations). Dr. D. Hill has identified 4 categories of chicks by temperature.1 Attentive growers will notice the simple cues that indicate temperature problems:

Comfortable:

Rectal temperatures are solidly at 104 to 105.5 �F (40-40.8�C). At the farm, the chicks will spread out, eating and drinking. The chicks have warm feet.

Hot:

Rectal temperature is over 106�F (41.1�C). The chick is panting. In the barn, a �chirping� distress sound may occasionally be heard. Chicks may move away from the heat source and line up along the wall. At the hatchery or during transport, the chicks cannot move out of their uncomfortable environment - panting is their only option.

Cold:

Rectal temperature less than 104�F (40�C). The chicks will be less active. At the barn, the cold chicks may huddle or �bunch� around the heat source or in feed lids. The low temperature chick has cold feet.

Struggling:

Rectal temperature just at 104� F (40�C). The chick has cold feet.
These chicks may be more difficult to pick out of the group without actually taking temperatures. Struggling chicks are diverting energy that should be used for growth and development to temperature maintenance.

Failure to achieve the thermoneutral zone

D. Hill has identified the most common problems that result in a failure of chicks to remain in the thermoneutral comfort zone1:

Overheating in the hatcher

The hatchers used in most hatcheries today were designed based upon a heat production of .11 to .12 watt/egg. Current research on today�s yield breeds indicates that the actual heat production is .14 to .3 watt/egg2. That�s a 27-173% increase in heat production! Hatcheries struggle to remove sufficient heat from high-hatching flocks.

Overheating in the holding area or during transport

Careful troubleshooting by taking rectal temperatures is needed to discover and correct overheating problems in the holding area or during chick transport to the farm.

The air temperature within the basket of chicks will be higher than the surrounding air temperature. One hundred 40-gram chicks at 90�F will produce 165 btus per hour. If the air circulation stops, the temperature within the basket will rise 1.5�F per minute3 resulting in an ambient temperature around the chicks of 104�F in about 10 minutes.

Chilling in the first 12-48 hours of brooding

Chicks do not have the ability to control their body temperature completely until they are 2 weeks old. They are reacting as a cold-blooded animal during the first few days. Floor temperature and insulation will be more important to chicks during this time than the air temperature.

Floor temperature in the area of the feed and water should be 90-92�F at placement. Smaller chicks from young flock sources have more trouble controlling body temperature than larger chicks: they will be the easiest to chill. Floor temperature is more critical to these chicks, and warm temperatures must be held longer to achieve maximum survival and performance.

Insulation from the cold and condensation inherent with concrete flooring is also essential. At least 5 to 7 cm of fluffy dry litter material is needed. Litter with a tendency to mat and hold moisture at the surface should be avoided. Thin floor coverage may be adequate for summer brooding, but doesn�t provide enough protection from cold concrete and moisture in the cooler seasons.

Impact of overheating and chilling

� Ernst et. al.4 found that heat stress at 104�F (environmental temperature) for one hour significantly reduced growth rate to 16 days. The weight difference persisted with no compensatory gain!

� Van der Hel et. al.5 examined feed intake at environmental temperatures over 95 to 97�F, especially during the first 48 hours. He noted that exposure to temperatures above this �upper critical temperature� resulted in decreased feed intake during the following 14 days, as well as increased mortality.

� Students at the University of Georgia6 submitted chicks to 55�F for 45 minutes. At 35 days of age, the liveweight of the cold-stressed chicks was 0.24 pounds (0.11 kg) less than the normally brooded controls.

� Increased metabolism required to meet the demand for heat production in a chilled chick requires increased oxygen. The heart works harder to meet this need, predisposing the chick to ascites later on.

� Although cold stress negatively impacts all chicks, those from young flock sources suffer the greatest impact, most noticeably reflected as �dehydration� or �starve-out� losses.

Beyond temperature: the rest of the story

Chicks also require feed, water and proper air quality to perform at the genetic potential.

Feed

Feed must be within the comfort zone of the chicks. Proper physical composition (good crumbles, not pellets or mash) will encourage uniform distribution of nutrients and efficient consumption by the chicks. Proper nutritional composition will give the chicks a good start. US integrators have experimented with reduced protein levels and reduced starter feed duration (as short as 7 days) with positive effects on cost and feed conversion. Careful management of these programs is necessary to avoid hurting flock uniformity and to avoid spiking mortality.

Water

Water must be easily available to the chick, and it must reside within the chicks� comfort zone. Nipple drinker height is important to adjust according to the actual size of the chick delivered. Pressure must be low enough to allow easy access to water for a small chick, while not wetting the floor. 360� nipples are easier for chicks of all sizes to trigger than nipples that must be pushed straight up. Check nipples by depressing them lightly from the side, to see how easy it is to access water. Older drinkers may become less responsive to the light pressure a small chick might apply.

Air Quality

Gases such as carbon dioxide and ammonia (in water vapor) are heavier than oxygen. If they are present in the house, they will tend to sink to floor level, displacing oxygen. The result can be the dual problem of ammonia blindness due to ammonia concentration at the floor, and ascites due to low oxygen at floor level!

Uniformity

Chick uniformity is influenced by temperature, access to feed, access to water and the influence of air quality. Any time a portion of the flock is forced to struggle to maintain temperature, to access feed or water, or to breathe, uniformity will suffer.

Remedial Measures?

Studies have shown that some of the damage caused by early stress is irreversible: a percentage of the genetic potential will be permanently lost. Measures can be taken to minimize the impact of short-term management lapses and the subsequent performance loss:

Culling

Avoid culling before day 7, especially in flocks composed of chicks from young breeders, mixed breeder sources or split placements. Give chicks an opportunity to start. By day 7, however, poor chicks should be obvious. These struggling chicks will serve as an infection source and a drain on feed and floor space. No amount of medication will �fix� these chicks. Cull them from the flock.

Walk the chicks!

When chicks are congregating in feed lids, along walls or in corners, frequent walking will force the birds to move out. This allows the chicks in the center to access feed and water, and may prevent �sweating� due to condensation in the groups. Attempt to correct the temperature, humidity or air movement issues that are causing the bunching in the first place, but try to manually keep the chicks spread out in the meantime.

Be alert to flock differences!

The identical environment may produce 104� rectal temperatures in chicks from older flocks but only 101-102� rectal temperatures in chicks from younger flocks. Don�t assume that the birds will always respond to management the same way!

Vitamins? Electrolytes? Antibiotics?

All of these measures may be helpful to the borderline chick. The unstressed chick doesn�t need them, and the severely stressed chick will probably be irreversibly damaged, and ultimately culled. The use of vitamins, electrolytes or antibiotics will not be deemed cost-effective by a large integrated operation. On a house-by-house basis, however, logical use may improve the performance of the struggling chicks.

Take time to Assess and Correct the Problem!

The first 48 hours go by quickly. It�s easy to let the problems go, especially since the rectal temperatures of most birds will be 104-105.5�F after 48 hours anyway. Don�t let it slip by! Failure to properly assess and correct problems flock after flock lets the genetic performance potential of every flock slip through your fingers!

� Check rectal temperatures of chicks in hatchers, holding areas and during delivery�make adjustments in airflow where possible to correct problems.

� Check rectal temperatures of chicks in the barn after placement. Make corrections in early management for the current flock, or adjust management for future flocks as needed. Be sure to walk chicks to keep them spread out, eating and drinking, until the corrections take effect.

� Observe feeding and drinking behavior.

� Note any repeated incidence of the indicators of poor air quality: ascites and ammonia blindness. Correct early air quality issues with improved ventilation and temperature control.

� Do not rely on remedial measures once damage is already done! Some of the lost performance is irretrievable!

References

1. Hill, D, 2001. The crucial first 48 hours in the life of a chick. Proceedings of Virginia Poultry Health and Management Seminar, Roanoke, Virginia, 2001.

2. Hulet, R. M. and R. Meijerhof, 2001. Multi- or single-stage incubation for high-meat yielding broiler strains. Proceedings of Southern Poultry Science and Southern Conference of Avian Diseases, Page 35.

3. Savage, S. The University of Georgia Cooperative Extension Broiler Tip, March, 1991.

4. Ernst, R. A., W. W. Weathers, and Jean Smith. 1984. Effect of heat stress on day-old broiler chicks. Poultry Sci. 63:1719-1721.

5. van der Hel, W., M.W.A. Verstegen, L. Pijls, and M. van Kampen, 1992. Effect of two-day temperature exposure of neonatal broiler chicks on growth performance and body composition during two weeks at normal conditions. Poultry Sci. 71:2014-2021.

6. Lacy, M. P., The University of Georgia Cooperative Extension Service Broiler Tip, January, 1994.

Many thanks to Dr. Donna Hill who has done most of the pioneering work on chick temperature as well as incubation and hatcher temperature and their effects on embryos and subsequent chick quality and performance.