Shadrach's Ex Battery and Rescued chickens thread.

[Perris]

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.

If it was constant (or as constant as a hen that might get off for a couple of hours a day during the first week - I've had such a hen) then the egg would just develop slowly. Development is faster and more problems arise if the temps get too high. From what I've been reading on artificial incubators, around 38 C / 99 F is ideal and the chick emerges in 21 days; if cooler it takes longer, if faster it takes less time.

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

I don't think that's a helpful way to think about variables. Biology isn't all or nothing, black or white; it's mostly grey. The temperature of eggs in a nest varies from those directly under the hen to those on the outside and even either side of the same egg under the hen. One of the explanations for hens turning eggs at the start of incubation is to ensure an even temperature gradient in the egg, before the chick has developed a blood system and can redistribute heat around itself.

 

[Perris]

I'm not firing on all cylinders

I do hope you're not going down with something again It's been a tough winter for you.

 

[L-plate chicken mum]

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

Cloudy here but did get an alert from Aurora Watch when it was still light! Continued with red alert (possibly visible from anywhere in the UK) until after dark.
One day I may be somewhere without all the light pollution & cloud cover

 

[Shadrach]

If it was constant (or as constant as a hen that might get off for a couple of hours a day during the first week - I've had such a hen) then the egg would just develop slowly. Development is faster and more problems arise if the temps get too high. From what I've been reading on artificial incubators, around 39 C / 99 F is ideal and the chick emerges in 21 days; if cooler it takes longer, if faster it takes less time.

I don't think that's a helpful way to think about variables. Biology isn't all or nothing, black or white; it's mostly grey. The temperature of eggs in a nest varies from those directly under the hen to those on the outside and even either side of the same egg under the hen. One of the explanations for hens turning eggs at the start of incubation is to ensure an even temperature gradient in the egg, before the chick has developed a blood system and can redistribute heat around itself.

As I mentioned earlier egg hatching is a complicated business, according to the studies at least.

If it was constant (or as constant as a hen that might get off for a couple of hours a day during the first week - I've had such a hen) then the egg would just develop slowly. Development is faster and more problems arise if the temps get too high. From what I've been reading on artificial incubators, around 39 C / 99 F is ideal and the chick emerges in 21 days; if cooler it takes longer, if faster it takes less time.

From what I've read a hen has the ability to regulate the progression of her eggs. They can do this to reduce the chances of a badly staggered hatch. Ideally the hen wants the eggs to hatch in the shortest time period so all the chicks have approximately the same development when they leave the nest.
This makes sense to me.

The main reason a hen turns her eggs in the first three days is to prevent the embyro from sticking to the inside of the shell is what I've read.

Thermal cycling happens in every natural incubation I can think of. I have yet to read anything that states after so many cycles within a specified temperature range the eggs wont develop. Yes, there is evidence that temperature over time accelerates or decelerates incubation time which is why the hen can compensate for this by how she distributes the eggs she's sitting on.

For the proposition that hatch rates are improved by picking the most recently laid eggs to have relevance someone needs to come up with a number and temperature range of cycles after which there is a reduction in viability. I haven't read any such evidence.
In my experience the nest has the greatest impact on hatchability.
I'm going to stick with whatever the hen thinks. After all, they've managed without our interference for thousands of years.

I don't play with the eggs. This is likely to lead to hatching problems.
I don't candle eggs.
The most I do is mark them and remove donations and breakages.

 

[Shadrach]

I do hope you're not going down with something again It's been a tough winter for you.

More a case of too many late nights due to social activities.

 

[notabitail]

 

[Perris]

Glad to hear the cause of your feeling you're firing on half cylinders is you've been out on the town rather than confined to bed @Shadrach !

From what I've read a hen has the ability to regulate the progression of her eggs.

Yes I've read that and believe it too

Ideally the hen wants the eggs to hatch in the shortest time period so all the chicks have approximately the same development when they leave the nest.

Indeed, and I think this is true for most bird species

For the proposition that hatch rates are improved by picking the most recently laid eggs to have relevance someone needs to come up with a number and temperature range of cycles after which there is a reduction in viability. I haven't read any such evidence.

Agreed. But no-one has looked for it to date I think (so there are no papers about it). Would you like to frame a suitable experiment for this year's breeding season, to be undertaken by any of us with broodies who might want to participate in a bit of citizen science?

I don't play with the eggs. This is likely to lead to hatching problems.
I don't candle eggs.
The most I do is mark them and remove donations and breakages.

Same here.

The Brazilian paper from 2016 you cited has a lot more on the action and functions of turning: here are some highlights

"Egg turning is a natural behavior of birds during incubation, and therefore, this practice was included in the artificial incubation process. Egg turning allows the diffusion of gases inside the eggs and between the eggs and the external environment. It is critical particularly during the first week of incubation, due to the long distance between the embryo and the shell, and to the high albumen density. During this period, the embryo depends on the diffusion of gases through the eggshell and the albumen to obtain O2 and eliminate CO2, because the embryo develops on the yolk surface and gases are exchanged directly by the embryonic cells. ... By days 13-14 of incubation, fetal metabolic heat production increases, and egg turning aids the circulation of air in the inner surface of the egg (external shell membrane) and air chamber, and allows heat loss by conduction, convection, and evaporation. However, egg turning is also important to prevent dehydration and incorrect embryo development (Wilson, 1991). Moreover, egg turning moves nutrients, facilitating their absorption (Brinsea, 2006). Egg turning is not as simple as it may seem. Egg turning frequency, axis of setting, angle, and plane of rotation influence in-ovo development, which may affect hatchability and chick quality (Wilson, 1991). Landauer (1967) demonstrated that chicken hens turned eggs approximately 96 times daily during natural incubation. ... During natural incubation, eggs are often exposed to temperature fluctuations in the nest, which may be caused by environmental temperature variations or changes in the attention hens direct to the eggs. Before the complete development of the chorioallantoic membrane, around day 12 of incubation (Tullett & Deeming, 1987), the embryo responds to the temperature gradient between the egg region in contact with the hen and the part of the egg in contact with the nest material, directing the blood flow to the colder region, regulating its internal temperature (Tzschentke & Nichelmann, 1997). After the complete development of the chorioallantoic membrane, the embryo is able to redistribute heat through its bloodstream (Turner, 1997), which allows regulating its temperature within certain limits. Both the direction of the heat flow and heat distribution through the bloodstream make the embryo less dependent of climate conditions around the egg. This shows that the embryo is able to react to minor temperature fluctuations inside the egg, and that it attempts to regulate its internal temperature within a very narrow range (Tzschentke & Nichelmann, 1997)."

 

[fluffycrow]

Cruella was broody on 5 eggs while we had two (and one minor) heat waves this summer. We had days where it got to 46°C, 43°C, 39°C. On the hottest days, she would not leave the nest until the afternoon, what it had cooled down significantly. This seems to indicate that females do have some control over how they allow outside factors such as temperature and humidity to influence their hatch. Cruella did not have any viable chicks hatch out of those eggs (I gave her some from the incubator on lockdown day, and those came to be the chicks she raised in August). She was about 8 months old at the time. Is it worth bringing female experience into this discussion? I think so. I do agree that nests play a big role in the success of a hatch.

@Perris Just an idea that came to mind after reading your last post on here. We know chicks can communicate through the egg, and they use this to synchronise hatching. If they were able to have some sort of control over their internal temperature, it is not wildly inaccurate to assume that they use it to synchronise their hatch. Faster growing embryos cooling down, while embryos that are a bit behind, warming up

 

[Perris]

@Perris Just an idea that came to mind after reading your last post on here. We know chicks can communicate through the egg, and they use this to synchronise hatching. If they were able to have some sort of control over their internal temperature, it is not wildly inaccurate to assume that they use it to synchronise their hatch. Faster growing embryos cooling down, while embryos that are a bit behind, warming up

Interesting thought; I have no idea how they would achieve that. Everything I've read so far on thermoregulation is far more basic (or is very directed toward 'improving' the chick that hatches to withstand heatwaves, and not much interested in embryonic development in its own right).

But one rather old paper involving some pretty brutal experiments concluded that there are critical changes around day 7 of incubation (when the embryo begins to have some control over its temperature) and again around hatch (when it begins to cope with cold much better); https://www.sciencedirect.com/science/article/pii/S0032579119511671 (open access; paper from 1951). It also suggests (table 2) that a temperature spike (up to 110 F / 43C) around 4 days into incubation doesn't need to last long to be fatal (50% dead in 10 minutes; 30 eggs used in the trial, but only the one trial undertaken, so the stats aren't great).

 

[Ladies-Eight]

Ex Batts good afternoon one and all!

Tea is ready.

Temperature is in the 70s and sunny.

Have a great day!