How sensitive are chicken eggs to temperature changes?

Discussion in 'Incubating & Hatching Eggs' started by phy, Oct 10, 2012.

  1. phy

    phy Out Of The Brooder

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    Hi everyone!!!

    I am a senior in college, who has raised chickens for years (but never incubated eggs). Since I'm studying engineering, for my senior project, I am constructing an incubator with automatic temperature/humidity control and automatic egg turning.

    My question is: how sensitive are eggs to temperature change? Some websites said a 0.5*F deviation will be enough to harm the embryo/get a poor hatch, but so far I can only find temperature sensors that have an error margin of +/- 1*F -- in other words, the sensors I'm looking at are not precise enough to detect a 0.5*F change in temperature.

    Thanks so much!!! I love BYC and its forum, and your expertise would be so much appreciated :)
     
  2. Ridgerunner

    Ridgerunner Chicken Obsessed

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    Think back to your thermo class on heat transfer. There are some mechanical engineering methods you can use on energy transfer if you flunked thermo. Air will heat up a lot faster than the solid egg especially with your fan. It will take a long time for the core of the egg to match changing air temperature.

    A half degree Fahrenheit will not cause serious problems in the hatch rate. A full degree Fahrenheit probably won't cause that many problems. What it will do is cause the eggs to hatch early if the average is warm or late if it is cool.

    Back to your problem. The important thing is average incubating temperature, not an instantaneous temperature as long as it does not get hot enough long enough for the core temperature to change dramatically. I've read different things about how much that core temperature can change and not harm the eggs, but I don't know that I believe any of them. Too hot is more damaging than too cool, but different eggs seem to have different toughnesses. Too much heat when they are first developing can lead to chicks developing with defects. That does not mean that each and every chick will develop those defects, just that some can. And at some point they will die. There is not a magic number where this happens to all of them, but things start to happen to some of them as the temperature changes.

    If you can maintain the temperature within half a degree to the core temperature of the egg, you will do great. You should be able to do much better than that. You'll find that you need to put your thermostat pretty close to the heat source so it keep cycling. That way you can keep the average incubating temperature much closer to what you want than than the air temperature because of the density of the egg and how much slower it heats up and cools off.

    Good insulation is very important in keeping the temperature steady. Another trick is to add thermal mass. That will give off or absorb heat and slow the rate if overall temperature transfer but the incubator I bought does not use that. Good insulation and regular cycling of the thermostat alone work well enough.

    Good luck on your project from a retired Civil Engineer.
     
  3. Ridgerunner

    Ridgerunner Chicken Obsessed

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    Since you are really interested in the temperature of the inside of the egg, you can use a water wiggler to measure the actual temperature inside the egg. Take a plastic Easter egg or something similar, fill it with a gel to simulate the density of the egg white, insert a sensor so you can track temperature, and see what is actually going on inside the egg. A graph that shows incubator air temperature versus inside of egg temperature would be a good addition to your project.

    You may need to do some calibration to assure your sensors are reading the same. Hopefully one of your professors can help you find a sensor that will record temperatures to that accuracy. If your school has an advanced degree engineering program they should have those somewhere.
     
  4. LTygress

    LTygress Chillin' With My Peeps

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    The answer to the original question is - not very. I have accidentally bumped my thermostat and sent the temp up to 108 degrees for several hours. But likewise, I have seen it go down to 96 degrees. But I'm still having close to a 100% hatch rate on fertile eggs. I also don't actually measure humidity. I keep water in the bottom of my incubator, and that's it. The only eggs that have not hatched were odd-shaped eggs, double-yolk eggs, or eggs from a hen that hasn't been near a rooster recently. I also just had my first 'exploding egg' (ugh) which was an odd-shaped one, since both ends were small.

    So in my experience, eggs are pretty hardy as long as you keep an eye on them. I got confused to hear some sources say the eggs should be 99 degrees, while other sources say 102 degrees. I just try to keep it BETWEEN 99 and 102, and it seems to do just fine.
     
  5. Ridgerunner

    Ridgerunner Chicken Obsessed

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    The difference in the recommended temperature is in the incubator type. In a forced air, the temperature should be the same all throughout the incubator, so you target 99.5 degrees. In a still air, since hot air rises, you can get a big difference in temperature depending on where you measure the temperature. The usual recommendation in a still air is 101.5 degrees taken at the top of the eggs.

    The core temperature of the egg is what matters, not the air temperature. You should try to get that as close as you can. But a lot of those eggs are pretty tough. You can be off some and the eggs will still hatch.
     
  6. hallerlake

    hallerlake Chillin' With My Peeps

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    The hen gets off her eggs everyday to eat and poop. The eggs temps drop some while she's off them. They survive. High temps seem to be more of an issue. Slightly high, and the chicks hatch ahead of schedule. Much too high, and they cook.

    In my experience, humidity is more important than slight temperature variations. I live in a rainy climate, and hatch breeds that are sensitive to too much humidity during the first 18 days.
     
  7. phy

    phy Out Of The Brooder

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    Wow!!! thanks so much, everyone! This information is extremely valuable and will help me a lot. I'll keep all of this in mind when I am building it. :)
     
  8. hallerlake

    hallerlake Chillin' With My Peeps

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    Be thankful you're not trying to hatch goose eggs. I'm told one has to cool them for twenty minutes every day, then spritz them with water. I guess that's what happens when Mothe Goose goes for her daily swim and comes home all wet.
     
  9. cmfarm

    cmfarm Chillin' With My Peeps

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    I hatched out a couple goose eggs and didn't do any of that. I set them the same a chicken eggs and they did just fine. As for the temperature that you hatch them I would think it could vary a little and not be a big deal. I think 99.5 is more of an average. I would think that chickens temps. can vary slightly just as humans can. An average human temp. is 98.6, but not everyone is that temp. Some a little higher and some a little lower.
     
  10. hallerlake

    hallerlake Chillin' With My Peeps

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    I guess I was mistold.
     

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