What did I do wrong?

[Junglebob]

I just finished hatching some eggs in 2 hova-bators with fans and wafer thermostats. I had automatic turners in them. Out of a total of 90 eggs I got 36 to hatch. I had a medical digital thermometer (acccurate to .2 degree) in a zip lock bag in the center. I checked the temperature and humidity 3 times a day, always when the heating element indicator light was off and temperature was in 100 to 100.5 range. They started hathing 3 days early, so I assume temperature was high, I know 99.5 is often recommended. Humidity was normally 50 to 55% except when they started to hatch and I planned to go into lockdown I upped it to about 65+%.

Is the center of the incubator the best place to read the temperature? I figured so since the thermostat was there.

I think fertility of the eggs should be good as someone hatched about 80% on eggs they got from me.

 

[Mrs. Feathers]

So many factors involved in getting these little chicks into the world....before, during and after we try to be mama hen in incubating them...
It sounds like you have a very similar bator set up to me. I would suggest observing when your temp indicator light comes on and what the low and peak is. For mine I like the light to come on at 99.5. This usually means a low of 99ish and a high of 100.5 to 101max giving me an average temp between 99.5 and 100. We hatch at an average of between 99.5 - 100. Lots of people seem to use 99.5 thought ...seems to be a learning curve and whatever works with all the factors at play at once. I keep our themometer sensor just outside of the middle of the bator (slightly away from the fan) and at mid egg height. It`s one of those external units with a sensor that we suspend in the bator. What breed(s) of chicks did you hatch? Congrats on the 36 you did get! I am learning that nothing is completely predictable with this hatching process....

 

[Junglebob]

Mrs, Feathers, Thanks for the reply. I hatched mostly black star, RIR and Barred Rock Cross, and some Silver Laced Wyandotte. Maybe the next time I try I'll have the thermometer closer to the front of the bator, which would be farther from the fan.

 

[Kedreeva]

Sounds like they are your eggs and not someone else's, so that rules out shipping issues. If you're past 21 but not at 25 or so, you may have late hatchers, unless you candled and they did not develop.

Your temp does sound high for a forced air incubator, but not out of healthy range unless there were other factors (like placement of thermometer). If your thermometer was at the bottom of the incubator but your eggs were higher (on an auto turner, as opposed to the floor where the thermo might have been) then the degree difference might have been enough.

If you are able to look at the remaining eggs, you may try cracking them open to see fertility (there's a guide somewhere here to an unfertilized yolk and a fertilized yolk, but I don't have its link), or to see what the time of death was in the cycle. That may give you a better idea of why you lost them.

You also want to make sure that you're not storing them too hot or too cold or too humid or too long or too short before incubating. Too hot, they may start incubation, to cold and they may die, too long and they may die, too short and they may not have settled from being moved around. We made the mistake of storing them a little too warm once and they all died while moving them from there to the incubator.