Ok.......I think I finely got it. Thanks to lots of links, reading, research, and plenty of advice from vets in here. I was so totally confused when I started, I thought I should post this so it just might help somebody. And PLEASE.....I don't mean to sound like a know-it-all. I just have really worked hard to figure this all out and want to try to help others as well.
Ok, so here is the thing. My first ever attempt to hatch was 28 golden buff eggs. They were from my hens, and fairly fresh. Long story short, only 3 hatched. I had 3 early quitters and 2 infertile. 20 of them were fully developed chicks that died just before they were due to hatch. Eggtopsy showed me they never turned in the shell so obviously didn't internally pip. I had to know why.
Research taught me I probably had the humidity a little too high. The chick got too big and couldn't turn to finish the process.
Ok....round #2
The next batch was 22 golden buff eggs also from my same hens. Keep humidity low this time I told myself. I didn't want that to happen again. So.....I ended up with 22 dehydrated "jerky" chicks!
Ok......research..............research........................research!
So then I asked a whole bunch of really stupid questions of some really patient people who tolerated me and kept trying to tell me there was no way to answer my questions. I didn't get it! What humidity do you use I asked. Depends was the answer. I was frustrated, and so were they. NOW, I GET IT!
During incubation, each egg needs to loose between 12% and 15% of it's body weight. That allows things to shrink up enough inside to allow the embryo to grow, but still have room to turn around to internally and externally pip.
What is also happening during this same time is the air cell at the top of the egg is getting larger. This air cell is where the chick will take its first breath after internally pipping.
If the air cell is full of water (from too high of humidity during incubation) the chick will drown. If the air cell is too small, there is no air in there to breath, and if the air cell is too large, the chick was probably dehydrated and is now dead anyway.
So....the correct answer to how high should my humidity be is: It depends on where your egg is at in the process of evaporating just enough, but not too much water from within the egg.
There are two ways to scale this.
#1 Look at and monitor the air cell by means of candling the egg. The problem here, is enough experience to know how big is should be at the time you check it. There is also the problem I have of not being able to see the air cell. I don't know if it is just these old half blind eyes, or my shells are thicker than some, or maybe because they are brown eggs. But what ever the reason, I just can't make out the air cell.
But, there is another way! I am putting a batch of 40 in tomorrow. I will weigh and mark every egg. Then, every 3 days, I am going to weigh them again. Each 3 days, they should have lost just about 2.4% of their original weight. If they are on track, fine. If they are too heavy, I need to reduce the humidity in the incubator. If they are too light, I need to increase the humidity in the incubator.
• To alter egg weight loss by 1%, humidity should be changed by about 5% Rh or 2 degrees F.
I will keep you posted, but from everything I know now, this should lead to a very successful hatch. It will be a long 3 weeks waiting to know!
And PLEASE veterans, PLEASE, PLEASE let me know if there is something here I am mistaken about.
Ok, so here is the thing. My first ever attempt to hatch was 28 golden buff eggs. They were from my hens, and fairly fresh. Long story short, only 3 hatched. I had 3 early quitters and 2 infertile. 20 of them were fully developed chicks that died just before they were due to hatch. Eggtopsy showed me they never turned in the shell so obviously didn't internally pip. I had to know why.
Research taught me I probably had the humidity a little too high. The chick got too big and couldn't turn to finish the process.
Ok....round #2
The next batch was 22 golden buff eggs also from my same hens. Keep humidity low this time I told myself. I didn't want that to happen again. So.....I ended up with 22 dehydrated "jerky" chicks!
Ok......research..............research........................research!
So then I asked a whole bunch of really stupid questions of some really patient people who tolerated me and kept trying to tell me there was no way to answer my questions. I didn't get it! What humidity do you use I asked. Depends was the answer. I was frustrated, and so were they. NOW, I GET IT!
During incubation, each egg needs to loose between 12% and 15% of it's body weight. That allows things to shrink up enough inside to allow the embryo to grow, but still have room to turn around to internally and externally pip.
What is also happening during this same time is the air cell at the top of the egg is getting larger. This air cell is where the chick will take its first breath after internally pipping.
If the air cell is full of water (from too high of humidity during incubation) the chick will drown. If the air cell is too small, there is no air in there to breath, and if the air cell is too large, the chick was probably dehydrated and is now dead anyway.
So....the correct answer to how high should my humidity be is: It depends on where your egg is at in the process of evaporating just enough, but not too much water from within the egg.
There are two ways to scale this.
#1 Look at and monitor the air cell by means of candling the egg. The problem here, is enough experience to know how big is should be at the time you check it. There is also the problem I have of not being able to see the air cell. I don't know if it is just these old half blind eyes, or my shells are thicker than some, or maybe because they are brown eggs. But what ever the reason, I just can't make out the air cell.
But, there is another way! I am putting a batch of 40 in tomorrow. I will weigh and mark every egg. Then, every 3 days, I am going to weigh them again. Each 3 days, they should have lost just about 2.4% of their original weight. If they are on track, fine. If they are too heavy, I need to reduce the humidity in the incubator. If they are too light, I need to increase the humidity in the incubator.
• To alter egg weight loss by 1%, humidity should be changed by about 5% Rh or 2 degrees F.
I will keep you posted, but from everything I know now, this should lead to a very successful hatch. It will be a long 3 weeks waiting to know!
And PLEASE veterans, PLEASE, PLEASE let me know if there is something here I am mistaken about.
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I had my eggies in an egg carton (homemade turner).
