I am totally interested in this!!!
I just asked this question not more then a few hours ago!!
Was looking for what the weight loss should be at the end of day 18 going into lockdown. I have been weighing the eggs for the last 3 years and doing this but used the numbers of 13% in 21 days which took me to .62% loss per day. Was thinking that it wasn't enough for me as we have had chicks fully formed that never hatched or piped the inner membrane. Thinking of upping it to .66% which would give me a loss of 11.88% by the end of day 18.
We also candle them and draw the air sac development on them each time. We try for day 3/4, 7/8, 14 and 18. Found that I have to kind of go with the average or if you have eggs you really, really want to go with them as a base for the humidity. Found the eggs from our pullets 10months of age and from our 1.5 year olds and even older girls have different weight losses and also from bird to bird and breed to breed. Ideal would to be have 10 small incubators on the go with each having the same style egg in them. OF COURSE THAT ISN'T GOING TO HAPPEN
As for your eggs candle them, the one that weighs the same as day 7 could have stopped but it could also be a hard shell and not loosing as much. We have made notes in the past that we thought that an egg or two was bad and the little bugger came into this world and proved us wrong!!
Can you give me the title of the book you found, would love to check it out! Thanks
Hi,
Glad somebody else is interested in this, I thought I was just being obsessive! The book is "Incubation A Guide to Hatching and Rearing" by Katie Thear, Broad Leys Publishing. The ISBN is 0 906137 25 X. Otherwise, just let me know and I'll type up the formula for you.
Since asking my question, I've found a sticky thread in the incubating section called "A guide to humidity, weighing and lockdown" -
https://www.backyardchickens.com/t/577310/a-guide-to-humidity-weighing-and-lockdown#post_7493364
That says hen eggs should lose 15-16% of their fresh laid weight to hatch. My Katie Thear book says 11-13% from starting to incubate to day 19.
I don't know what our eggs laid when they were hatched, I think they were pretty fresh when I got them (passed on from my cousin's friend).
This is the start of day 18 for us, I think (Tuesday evening, 21st Feb, and I put the eggs in the incubator Saturday evening, 4th Feb). Our eggs have lost too much weight if anything! From 13.8% up to 20%... the egg that hadn't lost much weight earlier on is at 13.7% now.
I have no idea whether you would expect the weight loss be higher for dry incubation, and this is now completely fine, or whether it's bad news.
I've candled the eggs too, we have some brown and some white eggs, and most of the air sacs look good, as far as I can see. I'm rather new to all this! Some of the eggs definitely look full, apart from the air sac, some don't, but I'm leaving them all in - I don't know enough to be throwing eggs out.
Please could you tell me if you dry incubate?
Our humidity has generally been around 22%, except when I tried to increase it because the egg weight generally seemed rather high. But it didn't seem to be possible to just increase it by a little, so I've left it alone since then. The incubator has a fan, and I alternate between worrying about drowning chicks and shriveling them up!
So now I think I'm going to put a lot of water in and go into lockdown....
