Reduction of bird heat stress. M. Czarick (University of Georgia)
Published:April 19, 2012
Dr. Mike Czarick, Senior Public Service Associate at University of Georgia, discusses the principles of keeping birds cold during hot weather during the XXII Latin American Poultry Congress, August 2011.
Many thanks great friends for all your contributions and suggestions. If I may add also about the addition of organic chromium into the feed at 500 grams per ton of finished feed . The feeds could be pelletized during hot weather to ensure that the birds gets the complete nutrients from each peck . They would need to peck less thereby exerting less energy during feeding.
Information is crucial, temperature causing heat stress is probably the most important aspect that increase the mortality rate here in the Caribbean region.
I forgot to mention in my earlier post that chicken don't sweat. As such, they do not lose heat from their skin except the minimal heat radiation from combs and wattles.They thereby resort to panting to release heat from the body, during heat stress which leads excess removal of carbon dioxide from the system. Carbonic acid is used to release significant amount of carbon dioxide. Depletion of carbonic acid raises blood PH. Which is called reactive heat stress alkalosis or metabolic alkalosis. Calcium metabolism is impaired under alkaline PH and so on.
In order to better understand acid-base disequilibrium in the body it is important to remember that "pH" refers to the existing relationship between acid and basic concentrations in a solution. So pH = [bases]/ [acids], which could be also somehow expressed as Ph = [HCO3] / [CO2].
When heat stress involves panting it means that there is hyperventilation, which decreases CO2 (carbon dioxide) concentration. If Ph = [HCO3] / [CO2], this leads to an increase in pH, called alkalosis. As the "cause" is the panting it is called "respiratory alkalosis".
Trying to compensate this "excess" of HCO3 (bicarbonate) and recover the "normal pH", the body "activates" the renal system after some hours and HCO3 reabsorption in the kidneys "is reduced" while HCO3 excretion with urine "is boosted".
As bicarbonate is a negative molecule (CO3H¯), it has to be excreted together with positive charge ions, such as calcium, sodium, potassium and magnesium.
That's why heat stress in layers may be associated with eggshell quality problems, because bicarbonate is excreted with calcium through urine.
So up to which point adding bicarbonate in water can be positive or negative for the animal? Depends on which metabolic situation is the bird and this is not easy to determine in field conditions.
Adding supplements to help animals under heat stress should be done in water better than in feed as feed consumption decreases. However if we mix different products we must be sure that they are compatible and will not interact among them producing caking and water pipes or nipple obstructions, because water supply is essential.
I completely agree that if we do not reduce poultry population density and implement environment refreshing measures with fans and evaporative cooling (always that environment humidity is not too high or we will produce a rebound effect), any dietary measure will not be enough.
Another mistake people make is to build low houses with three-tier cage installation. The height of the building helps a lot to boost natural ventilation. Another mistake is to make the width of the house to accommodate 4 rows of cages instead of two or at worst three rows. Roofing materials is also a factor. Asbestos would hold heat in the day and throws them into the house during the colder period of the day which is basically in the night. Zinc roofing sheets would pick up the radiant energy and through them into the house immediately in the daytime thereby wrecking the havoc immediately. Light or white colored long span will reflect some and throw in some. The best is to use straw thatch on top of the roof during the heat periods. Though straw materials attract pest. Rather best is to use silvery roof reflectors as roof covers.
A component of Heat Stress is the production of heat by metabolism. One way metabolism might be minimized during the hottest part of the day is to have the birds sleep period from around 11am to 5pm.
They will stop eating and generating heat by exercise with the result that they will produce less heat internally.
Unless something in a bird's diet reduces its metabolic rate additives will not be much help.
Breeze sweeping away the hot moist air chickens are breathing out helps a lot otherwise they are breathing warmer more humid air than that of the ambient conditions.
For this to work well the birds heads need to be in the breeze.
Keep up the good work !
David Evans You have to be careful about having the birds sleep during the hottest portion of the day. Though heat production does decrease when a bird sleeps the problem is that our research has found that the bird body temperature actually increases a degree or two because heat loss goes down because no heat is lost from the underside of the bird.
Thank you for the advice Mike. I would be keeping the wind-chill fans operating to endeavour to keep the birds feeling the desirable temperature for their age/weight. Perhaps I should have said that but perhaps that would be insufficient - a comment on this would be welcome.
Layers like to perch when sleeping. Are broilers too heavy to perch or just not inclined to if they had perches available ?
David Evans I could see removing feed from the birds during the day to minimize heat stress (which of course would reduce growth) and keeping good air movement over them its just that you don't want them to sleep for a long period of time. I am an advocate for not giving the birds long dark periods at night during times of heat stress because it can cause the body temperature to be higher at night than during the day.
Hope this helps.
Rahat Hussain The 170 value (temperature F + Rh) really has limited use because it does not take into account air speed. The higher the air speed the higher the value can be.
In my homeland of Trinidad, where we used open sided houses, we found that fans angled to approximately 45 degrees inside of the house helped reduce heat stress during periods of high temperatures, Birds were also fed early in the morning and in the afternoon when temperatures were a little cooler. Feeding birds during the hot part of the day resulted in a lot of wasted food as birds were not digesting the feed. Water was cooled with and water tanks that were outside were painted white to reflect the heat from the sun. Water soluble Vitamin C and B vitamins were also provided to the birds at all times.
Robert Huggins our research has indicated that installing fans at a 45 degree angle does not produce maximum bird cooling. Installing 36” fans in pairs 40’ on center did a very good job of mimicking the air flow patterns seen in tunnel houses
Dr. Mike Czarick Dear prof nowadays we see so many big fans like 72” or 78” what do you think about their performance against high static pressure, especially in humid areas.
SOHAIL BASHARAT Generally, speaking larger fans are more energy efficiency than smaller fans. How well they hold up to high static pressure will vary from fan to fan based on how they are designed. In general, the larger fans can perform well under high static pressures. The 72" fans and larger are best suited for very large broiler houses (60 X 600') or large commercial layer houses.
Zahoor Sakafi
My comments on how to control E.Coli after IB, given on June 29,2018 in forum of Engormix may be of some use for you.
Regards
Dr. M.Akram
Replying to Dr Charles Ibe
Aluminium is the best reflector of infrared (heat) radiation so an aluminium paint seems an attractive solution. It will reflect solar infrared radiation very effectively. However it will also reflect infrared radiation coming up from the inside of the poultry house back down again, which is not so good. (At night one would want it be escaping.)
So, what one really needs is a coating for the iron roof, which is like a one-way mirror - reflects on one side and allows transmission from the other side.
In recent years special white paints with this property have been developed - they are excellent reflectors and very good emitters/transmitters so are excellent at reflecting in the daytime and allowing infrared radiation to pass out through them at night.
They can be located easily on the internet.
Message for Dr Charles Ibe
Look at pages 26 and 27, in particular, of http://www.ata.org.au/wp-content/uploads/cool-roofs.pdf
This may be some help. Also you may search for emittance values of metals and compare aluminium and iron. That may guide you as to the best type of metal roofing to use.
Note - the best solution is different for hot climates (such as yours) and cold climates so views differ at times.
Dr Ibe please do not follow this information. Aluminum is fine to use for poultry houses. That being said poultry house ceiling must be insulated if you want to minimize heat stress
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