Shadrach's Ex Battery and Rescued chickens thread.

[Perris]

I missed the Aurora Borealis last night! Looks like it was fab here!
https://www.bbc.co.uk/news/uk-wales-68465549

 

[BDutch]

Batty Ol' Hens Broody Tincture

Why do you think incubation of the first egg starts when a hen goes to lay her second egg? Having watched hens laying eggs the posture to lay and the posture to hatch are very different and I suggest that the eggs already laid do not reach start incubation conditions when the hen lays subsequent eggs.

I wonder how long it actually takes to sit to actually start the development of a fertile egg. If a hen has to sit non stop for 12 to 18 hours to actually start the embryo going, it would make it all clear for me.
If so the pre-brooding has no effect on the development of a fertile egg.

PS Most times I don't read the English research reports, only summaries or an interesting page, because in general these are quite difficult to read for me. So if you can point out the most important pages I would be grateful.

PS2
About the early development. Translated from Dutch (Radboud university):
In the stage from 10 p.m., the somites become visible, which have formed from the mesoderm to the right and left of the neural walls. After 24 hours, 4 to 5 pairs of segmented blocks can be distinguished. Later, these structures will differentiate into vertebrae, ribs, part of the skin and the back muscles. Only the area of the head protrudes above the area pellucida. In the drawings below from Patten (1920) one can see the chorda (notochord) at 24 hours in the area of the 'anterior intestinal portal'. This structure marks the differentiating foreintestine formed like a blind pocket surrounded by endodermal tissue. The neural walls end in a neural pore at the front and on the side of Hensen's knot they become smaller and more apart and end in the sinus rhomboidal. Sometimes the outer-embryonal blood vessels can already be seen in the vasculosa area. Later, they will make contact with the vitellian arteries and veins formed in the embryo via the ductus omphalosentericus.

https://www.vcbio.science.ru.nl/virtuallessons/embryology/chicken-22-28h
(They used literature : Development stages after 10-28 p.m., according to Patten (1920). And new research/testing.)

 

[Perris]

I wonder how long it actually takes to sit to actually start the development of a fertile egg.

Yes, that's exactly the question we're pursuing.

If a hen has to sit non stop for 12 to 18 hours to actually start the embryo going, it would make it all clear for me.

It would be so easy if so, but sadly, there's no known mechanism that registers time in an egg. But things do change with temperature (amongst other things).

 

[BDutch]

The relevant bit of the second (which is a really useful document, thanks for linking!) is this (under Landmarks of Embryonic Development):

Yes, that's exactly the question we're pursuing.

It would be so easy if so, but sadly, there's no known mechanism that registers time in an egg. But things do change with temperature (amongst other things).

Thanks Perris for posting the most relevant parts.

 

[BDutch]

I found this in a Dutch presentation for commercial hatcheries. About collecting the hatchery eggs.
. „When you pick up eggs that have just been laid in the middle on a paper tray, they may not cool down to 25 degrees Celsius within 6 hours. The development of the embryo then goes too far and this will lead to embryonic mortality,” says De Lange.

Source: https://www.pluimveeweb.nl/artikel/...ng-wanneer-broedeieren-niet-uniform-afkoelen/

 

[Perris]

I found this in a Dutch presentation for commercial hatcheries. About collecting the hatchery eggs.
. „When you pick up eggs that have just been laid in the middle on a paper tray, they may not cool down to 25 degrees Celsius within 6 hours. The development of the embryo then goes too far and this will lead to embryonic mortality,” says De Lange.

Source: https://www.pluimveeweb.nl/artikel/...ng-wanneer-broedeieren-niet-uniform-afkoelen/

that's very useful; thank you.

 

[Perris]

I found this in a Dutch presentation for commercial hatcheries. About collecting the hatchery eggs.
. „When you pick up eggs that have just been laid in the middle on a paper tray, they may not cool down to 25 degrees Celsius within 6 hours. The development of the embryo then goes too far and this will lead to embryonic mortality,” says De Lange.

Source: https://www.pluimveeweb.nl/artikel/...ng-wanneer-broedeieren-niet-uniform-afkoelen/

my turn to struggle with a foreign language and google translate! Perhaps you can help again?
On the webpage the first paragraph is translated by google as
„ The body temperature of a hen and thus the hatching temperature is 41 degrees Celsius. As long as the temperature of the hatching egg is higher than 25 degrees Celsius, the embryo continues to develop to a limited extent. When an egg cools quickly, the breeding duration will be longer and with slow cooling the breeding duration is shorter. If hatching eggs do not cool uniformly, there will be a greater spread of results ”, says poultry specialist Gerd de Lange of incubator manufacturer Pas Reform.
could what is translated as 'the breeding duration' also/instead be translated as 'viable' / 'viability' / some word indicating still alive and able to continue development in due course?

 

[Shadrach]

The first paper is full of detail but the only trigger I see there relevant (to the question: what initiates incubation?) is temperature, in particular, this bit: "Although the interaction among several physical agents during incubation influences in-ovo development, temperature has the strongest influence (Freeman & Vince, 1974; Decuypere & Michels, 1992; Meijerhof, 2009), because it can hinder, promote, or maintain embryonic and fetal development, as well as determine its rate and duration. Eggs are submitted to different temperatures from reception of the eggs at the hatchery until hatching. During storage, temperature is reduced to delay embryonic development. Subsequently, eggs are heated to reactivate embryonic development immediately before setting. "
When a hen goes in to lay another egg and sits on the egg(s) already there, she heats them, variably of course, depending on her temperature, their position etc.. Anyone with laying hens can test this easily.

Also relevant, "In chicken eggs, eggshell temperature remains low during the first week of incubation and increases during the second week, reaching a temperature plateau around day 14-15 of incubation", so a relatively low temperature may be enough to activate the embryo to start growing, and maybe it gets high enough, at one or another spell of the hen sitting to lay, to trigger it in one or another egg. According to Assersohn et al (linked before) "Cell division begins approximately 2 hours after fertilization, and by the time the egg is laid, the germinal disc typically contains thousands of embryonic cells" so I don't think it can need very long or a higher temperature than a sitting hen normally generates to get the process started.

I haven't worked through their references yet; did you have something specific in mind in that paper that I've missed?

No, just posted as general interest.

 

[Perris]

According to Assersohn et al (linked before) "Cell division begins approximately 2 hours after fertilization, and by the time the egg is laid, the germinal disc typically contains thousands of embryonic cells" so I don't think it can need very long or a higher temperature than a sitting hen normally generates to get the process started.

Thinking further about this, the process (development of the embryo) starts with fertilization, and continues as long as it's in the nice warm hen's body, and continues after the egg is laid for a time depending on the temperature, until it drops to about 25 C (according to that Dutch firm). So actually what we call incubation is re-starting it, and it would seem that it only needs to get to a temperature of 25 C or more to do so (all other things - like humidity - being equal, and conducive to egg incubation of course).

If a hen's normal body temp is 41 C, how long would she need to sit on a previously laid egg to reactivate it?

 

[Shadrach]

I'm not firing on all cylinders but if I've understood correctly the idea is that perhaps thermal cycling of an egg reduces it's viability and picking the most recently laid eggs to put under a broody increases the hatch rate because they've undergone n number of thermal cycles.
A temperature of 25C gets mentioned as a cut off point where below this temperature there is no development and above, the egg developes.

I've had nest that have been exposed to direct sunlight in Catalonia which would heat an egg way beyond the 25C mark. I think, during the spring and summer months in Catalonia the nest temperature in a coop nest wouldn't drop below 25C for most of the day and maybe not at night either during the summer yet hens have sat and hatched perfectly healthy chicks under these conditions.

It is difficult to accept the some will and some won't type arguement when dealing with something as specific as temperature.

Trying to match the science to reality makes me think that if the eggs do undergo thermal cycling it isn't a critical feature.