Chicks hatching at different rates

[EggSighted4Life]

If curled toes and spraddle leg are caused by heat and or humidity fluctuations why was the one exposed to the most of those hatch a normal chick?

Welcome to BYC!

There can be many causes.. and individual egg nutrition should not be dismissed, in addition to hot or cold spots, etc already mentioned. Are they from your flock?

I wouldn't ditch the bator.. but learn to work with it. Every bator will have it's ins and outs. For example I hate the nurture right 360 that so many are fond of and prefer Styrofoam or at least side walls so eggs or chicks can not fall out when I open the lid..

Possible causes of embryonic mortality and specific conditions seen start around page 51 of the following link..

https://www.hubbardbreeders.com/media/incubation_guideen__053407700_1525_26062017.pdf

 

[Chikitty]

Thank you, very interesting information! From the previous answer and the link you provided the temperature and humidity not being consistent throughout the incubator seems to be the most logical answer.
With a forced air incubator how do you combat that issue? I understand having a separate thermometer/hygrometer would tell if the settings on the incubator were accurate, but how does that keep from having said hot/cold spots within the incubator?

 

[Huntmaster]

Thank you, very interesting information! From the previous answer and the link you provided the temperature and humidity not being consistent throughout the incubator seems to be the most logical answer.
With a forced air incubator how do you combat that issue? I understand having a separate thermometer/hygrometer would tell if the settings on the incubator were accurate, but how does that keep from having said hot/cold spots within the incubator?

By getting to know where they are and not using those areas if possible, finding sweet spot. Rotating eggs around in incubator regularly to even out the incubation in eggs can help also. But getting to know where they are and how much difference in temp would tell you if it's worth working with or not. But you did get eggs to hatch so I would have to believe with some testing/work you should be able to make it work.

 

[EggSighted4Life]

With a forced air incubator how do you combat that issue?

Enough.. I move eggs to a new spot in the bator every day or two or at candling.. as part of my standard hatching practice.. and to get hatches dialed in to within hours if possible.

Forced air and auto turning decreased my hatch rates as compared to still air and hand turning.

I once had a long power outage when not home midterm incubation.. with known hatching stock.. and got 50% bent toes at hatch.

I have nutrition dialed in and bred Silkies for a short while, but with attention to detail disorder in full swing as it is for me, one specific (Silkie) hen's eggs threw splay legs.. Whether one chooses even more dietary supplementation, facing that possibility at hatch, or culls or otherwise eliminates from breeding stock however they see fit, the offender of weak genes.. is a consideration for the keeper.