Shadrach's Ex Battery and Rescued chickens thread.

[Ladies-Eight]

Ex Batts good afternoon one and all!

Tea is ready.

Temperature is in the 70s with strong gusty winds expected.

Have a great day!

 

[Shadrach]

When a hen goes to lay the second egg in the clutch, she is unavoidably starting to incubate the first egg laid. I have read nothing to date (and I've read a lot ) to indicate that there is some physical or biological mechanism in the egg that can distinguish between this short incubation period and incubation proper. After dropping the second egg and sitting on it (and egg 1) till the bloom's dried, she stops sitting/incubating, and goes about her daily business, till she comes back the next day to lay the third one, and thereby temporarily incubates egg 1 again, and now egg 2 as well. And so it repeats until she deems the clutch complete, by which time egg 1 might have been partially incubated say 6, or 9, or 12 times. I think it quite possible that the earliest laid eggs in the clutch start to develop and then die early through this stop-start process of growing the clutch. It would be relatively trivial to test this hypothesis.

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 have on a few occasions marked eggs by day, 1,2, etc. Also, whether correct or not, I've removed the latest eggs to whatever number I've wanted her to sit on, leaving the earliest in the series in the nest. The eggs hatched okay.

There is also the matter of those hens who hatch outside on an unregulated clutch and hatch what they laid bar a few percent over a number of hatches.

 

[Perris]

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 have on a few occasions marked eggs by day, 1,2, etc. Also, whether correct or not, I've removed the latest eggs to whatever number I've wanted her to sit on, leaving the earliest in the series in the nest. The eggs hatched okay.

There is also the matter of those hens who hatch outside on an unregulated clutch and hatch what they laid bar a few percent over a number of hatches.

Clearly individual differences in behaviour will apply here. My hens vary in behaviour between about 20 mins to lay an egg and sitting there for around 2 hours. What triggers the start of incubation conditions to which you refer? Is it absolute, or might some hens trigger it prematurely sometimes or even normally? And what exactly are they?

 

[Shadrach]

Thanks for your thoughtful and informative post @fluffycrow ; lots of good points there, not least raising awareness that different people can have different reasons for doing the same thing. What immediately springs to mind for me on broodies v incubators is 1. huge difference in scale - that's why incubators are used commercially, and have such a long history (the ancient Egyptians designed them even before the Greeks started writing!) and 2. all eggs start together and endure the same (more or less) conditions in an incubator, certainly by comparison with being under a hen.

@Molpet thanks for your input too; personal experience is the reality check on all our ideas! None of this is simple, and multiple types and possible causes of the variation is why it's tricky to unravel this one.

This egg hatching business is complicated.

https://www.scielo.br/j/rbca/a/ZFYLhJkZ8VSVpXZSJmCcKvr/?lang=en

https://original-ufdc.uflib.ufl.edu/IR00004437/00001

 

[Perris]

This egg hatching business is complicated.

https://www.scielo.br/j/rbca/a/ZFYLhJkZ8VSVpXZSJmCcKvr/?lang=en

https://original-ufdc.uflib.ufl.edu/IR00004437/00001

Thanks for the links; I shall read them in the morning when I am fresh. Need to sleep now; goodnight.

 

[fluffycrow]

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 have on a few occasions marked eggs by day, 1,2, etc. Also, whether correct or not, I've removed the latest eggs to whatever number I've wanted her to sit on, leaving the earliest in the series in the nest. The eggs hatched okay.

There is also the matter of those hens who hatch outside on an unregulated clutch and hatch what they laid bar a few percent over a number of hatches.

I've spent hours observing the females laying. They don't all have the same laying positions, nor take the same time on the nest. Some girls sit for 30, 20 minutes, and I've clocked others at two hours. Some hens will barely touch the eggs, not even sitting after laying, and others will spend hours sitting on eggs, laying the eggs, and then sitting back down before leaving. I should mention that the bird that take the longest to lay have never gone broody in their lives, so that's something interesting to see. The batch in which 14 out of 15 eggs hatched successfully, Cruella laid, and cared for completely on her own. Batches where I took a much more active role, have not been as successful. I think this matter is complicated, and don't have enoigh evidence to dismiss this hypothesis. The first eggs might have some kind of early developement; I just don't think it leads to their death later in developement

 

[Shadrach]

It was quite a pleasant afternoon weatherwise. A bit of a shock after yesterdays snow. Two and half hours today.

Henry demonstrating the more mature, empathetic attitude to hen care to Dig.

 

[Perris]

This egg hatching business is complicated.

https://www.scielo.br/j/rbca/a/ZFYLhJkZ8VSVpXZSJmCcKvr/?lang=en

https://original-ufdc.uflib.ufl.edu/IR00004437/00001

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?

 

[Perris]

their death later in developement

good point. Cause of death is unknown at this point. Let's try to keep the focus on the first 5 days, because that's where the conflation with infertility resides.

 

[Perris]

This egg hatching business is complicated.

https://www.scielo.br/j/rbca/a/ZFYLhJkZ8VSVpXZSJmCcKvr/?lang=en

https://original-ufdc.uflib.ufl.edu/IR00004437/00001

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

"6.4 to about 25.5 h post-ovulation (oviposition)-- Continued division and growth; cells segregate into groups for special functions. Several hundred cells at oviposition. Between oviposition and incubation -- No growth; embryo is inactive (if embryo is held below 76°F or 25.5°C, which is physiological zero); normal storage temperature is 55° to 65°F or 13° to 18°C."

So temperature is identified as the (only) trigger here. And obviously a normal hen naturally generates the right temperature to incubate eggs when she sits on them.

Another useful bit is this (under Troubleshooting)

"2. Sign: Eggs candle clear; broken out eggs show enlarged germinal disc; no blood. Fertile. Some are termed "blastoderm without embryo." Causes: 1. Eggs stored too long. They should be stored<7 days. 2. Eggs held under poor conditions, temperature too high or too low. Fluctuating temperatures. Temperature should be 60°to 65°F (15.6° to 18.3°C). 3. Fumigation improper -- too severe or done between 12 and 96 h of incubation. Incorrectly spraying or foaming eggs with disinfectant. 4. Eggs damaged during handling and transport by jarring, temperature shock (temperature increased or decreased too rapidly), etc. 5. Eggshell sealed -- respiration inhibited. 6. High temperature in early incubation. 7. Very young or very old breeders. 8. Heredity, inbreeding, chromosome abnormalities, or parthenogenesis. 9. Breeder flock diseases. 10. Failure of a basic organ system to develop normally. 11. Egg wash temperature too high. 12. Egg-borne infections (e.g., salmonella). 13. Drugs, toxins, pesticides, etc. 14. Infrequent or incomplete egg collection." And points 3 and 4 then continue the analysis for D1-3 mortality and D3-6 mortality.
That's comprehensive on possible causes of early mortality, and again temperature features prominently.