Good information, thank you!Seems like a workable method Fuzzi, though the turning seems redundant from what I've read too. Here's an overview of current thinking on the topic:
Incubation
First note that research on this is almost entirely focussed on how to improve hatchability and quality of chicks incubated in huge numbers in artificial incubators; when hens and natural incubation get a mention, it is almost always merely as a base reference point. Ironically, one of the latest techniques being tried (SPIDES) sort of mimics the behaviour of a hen building a clutch, so maybe one day soon I’ll have an answer to the question I’m really interested in (which is the effect of repeated short term heating and cooling on the developing embryo as the broody or other hens sit on it to build the clutch); but I’ll just park that for now and focus on the key takeaways for a backyard wannabe broody assistant.
Best results have been got with eggs stored between 3 and 7 days; this graph (from Brake et.al. Egg Handling and Storage 1997 Poultry Science 76:144–151) illustrates it.
View attachment 3765570
The albumen changes over time (notably, its ph), and its suitability for the embryo drops off more or less sharply after the first week. But very fresh isn’t ideal either (that chimes with my emergency Venka hatch where the only one that didn’t make it was the freshest one).
The concept of ‘physiological zero’ has been superseded by the notion of ‘embryonic diapause’ because there is development going on in the blastoderm (and some cells are dying) while in storage. There is at least one critical point in this early development where, if conditions are adverse, the mass of identical/ nearly identical cells that the blastoderm is, cannot differentiate into the wide variety of cell types needed to make all the different bits of the body of the chick (called pluripotency), and that leads to early embryonic mortality (usually mistaken for infertility).
Eggs that are stored longer may develop more slowly (than those stored for shorter times) when they resume development and not catch up, which could lead to them being left behind when the broody leaves the nest (because she has to look after the chicks that hatched earlier). Or they may notThis quote is specially for Shad
: “the biological age of an embryo from a 14-d stored egg lags behind that of an embryo from a 4-d stored egg (Fasenko and Robinson, 1998). This observation was made even though the chronological ages of the embryos were the same. In examining embryonic development every 3 hr for the first 12 h of incubation, it was determined that the development of the embryos from 14-d stored eggs began to lag behind as early as 6 hr into incubation. Further to this, it was determined that not all embryos responded the same way to long-term storage. Some embryos of long-term stored eggs, even after exposure to normal incubation temperatures for 12 h, had not initiated any development. Other embryos advanced in development, but not at the same rate as embryos from short-term stored eggs. Perhaps the most interesting result obtained was that there were some embryos from long-term stored eggs whose development was equal to that of the short-term stored eggs” Fasenko, Egg Storage and the Embryo 2007 Poultry Science 86:1020–1024.
Turning: the focus in the research papers on storage stage is almost entirely focussed on temperature and time. Even relative humidity barely registers; the tolerances there are huge. As a personal aside, I never turn eggs in storage and (as I have learned from this reading) my hatch rate is sometimes better than the industry standard. The Brazilian paper observations on turning, which are very useful and relevant to the incubation stage, I already gave in an earlier post, so I won’t repeat here.
Other relevant tidbits:
Eggs laid by older hens develop faster than eggs laid by younger hens.
If you manipulate the temperature going in or out of storage, do it slowly. Abrupt temperature changes can be damaging.
A lot of detail remains unknown, e.g. exactly how many embryonic cells need to survive storage in order to successfully resume development, and this, from one of the leaders in the field, from 2021: “Our understanding of the molecular mechanisms underlying the relationship between storage temperature and development stage within the DW [diapause window] is rather limited”.
Good luck with the hatch when it happens!
I love the way Tintern's looking over his shoulder as well as the heart shape his wings make. I also think I see Fforest's rear feathers facing backwards so to speak as he does an emergency stop (he didn't crash into Quenell at all).
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