Poor hatch rate

[CKHuggins]

Nearly 50% of my eggs did not hatch. Looks like they were nearly fully developed, but just stopped growing / or didn't hatch in the last days before hatch. 40% humidity for 18 days then 70+% for last few. Home made incubator (mini fridge) with little giant egg turner, forced air. Multiple thermometers, incubator warehouse thermostat. Set my egg-o-meter to 99.5 deg. Some chicks hatched 2 full days early!!!! All hatched before the 21st day. So I am thinking my temp is too high. Any other pointers?

 

[CluckyCharms]

So sorry for the hatch rate.

Questions:

Were they shipped eggs? (did you order them online and have them sent to you) If so - do you know how long it was from the time of collection to the time of shipment? How long did the package take to get to you from the point of origin?
What breed were they?
Were they under a broody hen at any point after laying and if so, how long?
If they weren't shipped eggs, what temperature did you store all the eggs at until you had the clutch amount you wanted?

 

[CKHuggins]

The eggs were all fresh from my chicken, I have mostly Blue Cochins, a couple of New Hampshire reds, Baird rocks, and a few other egg layers. Also have Silkies, only tried 3 of their eggs, and they all took. The eggs were all less than a week old. Collected each day, and stored at room temp (75 ish deg.) this is only my first batch of hatching, so any advice would e greatly appreciated. I have done a ton o reading on this site before I even built the incubator.
Thanks.

 

[CluckyCharms]

Hmm...I would have assumed shipped eggs would fully contribute to the cause, but since they're your own eggs...well..nope. lol I'm hoping someone else with more experience will chime in to help you!

I do have a question though: Forced air incubators are built in such a way that they 'force' the heated air around the incubator via a fan. Since you used a mini-fridge - how many ventilation holes (if any) were auto-drilled in through the exterior and into the interior of the mini refrigerator? Were they drilled in such a way as to promote fresh air being drawn inside via many areas, so the air from inside your house could circulate around? I don't know much about incubating eggs, but I do know that fresh air is a big part of it and they need a constant supply (hence all the holes and vents in commercial bators). Refrigerators are sealers (they're built to keep things cold and thus the seals everywhere) Other than possible ventilation issues (not enough fresh air getting inside) I don't know why your hatch rate was so low - everything seems like it was a very comfortable environment for the eggs.

 

[CKHuggins]

Thanks for the input, I am going to try and add additional ventilation, it is limited right now, but its not "sealed" by any means. I have a 1/2 hole toward the top, and there is a lock assembly at the bottom of the fridge that leaks a lot of air, I figured those two things would be good enough. maybe not. I am also going to re-engineer the fan to make sure it is drawing up the cooler air from the bottom of the incubator.

 

[CKHuggins]

Does anyone have a reason other than too much heat for the early hatch?

 

[johnderosa1]

I built my own incubator as well and ran into early hatches the first few times i used it. My problem was due to a higher average temperature than anticipated. The temperature would continue to rise well after the thermostat shut off due to the size of the heating element and position of the probe. Not only did this increase the average temperature it also caused temperature differences in different parts off the incubator - even with a strong fan. I was able to solve my problems by adding a dimmer switch to the circuit and positioning the thermostat's probe directly down wind from the heating element. With the dimmer's power set almost all the way down and the quicker thermostat cycling due to the new probe location I am able to keep an almost constant temperature in all parts of the incubator.

John

 

[CKHuggins]

I am using light bulbs for heating elements, I started with 60 watt, but downgraded to 40 watt bulbs for the same reason. The 40 watt bulbs cool off pretty quickly and do not spike the temperature, however i have just noticed the temperature is only accurate at the location of the probe, so I am going to re- engineer the fan to draw air from the bottom of the incubator to the top and mix the air more thoroughly. I have the probe at the heidth of the eggs, but i use the lower part as a hatcher, so i need the temp to be right there too.