Landrace/adaptive breeding discussion

[Shadrach]

What?! Nature vs nurture is complicated???

I don't believe I said anything about nurture vs nature. It's one of those meaningless expressions that gets tossed about without anyone defining either, much like survival of the fittest.

 

[LaurenRitz]

I don't believe I said anything about nurture vs nature. It's one of those meaningless expressions that gets tossed about without anyone defining either, much like survival of the fittest.

No, you said "The whole genetics completely determines behaviour is just plain wrong. It's not that genes don't play their role but there is a balance in there somewhere between environment and genes."

Therefore, both genes and environment need to be taken into consideration.

 

[LaurenRitz]

Ok. From my records, which are anything but complete and cover only 4 hens that go broody.

1-BA. From first lay to first broody was 70+ eggs. All her eggs were taken by a snake. From broody 1 to broody 2, 18 eggs. Broody 3, 94 eggs. Broody 4, 78 eggs. Currently raising chicks.

2-JG. To first broody was 108 eggs. Broody 2, 72 eggs. Broody 3, 72 eggs. Currently sitting.

3-BA. To first broody was 70 eggs. All eggs lost. Broody 2, 20 eggs, Broody 3, 72 eggs.

4-MJ. To first broody was 52 eggs. She wasn't taking care of herself and died on the nest

I do see one possible pattern. When not allowed to continue the broody cycle, they appear to go broody again more quickly.

 

[Perris]

If you find the source at some point in the future, I'd like to read it too.

I haven't found it yet, but in looking I have rediscovered something of relevance to this thread and perhaps of interest to its readers.

It's from Birkhead Bird Sense 2012, the chapter on touch: if eggs are removed as they are laid, some bird species will keep laying daily or thereabouts, until they have laid many more than is normal for that species. In these species, the brood patch plays a vital role in determining how many eggs the female lays. "If the eggs are not removed, touch sensors in the brood patch detect their presence in the nest and then, via a complex hormonal process, allow only the 'right' number of ova to develop in the ovary". But if the eggs are removed, they get no tactile stimulation of the brood patch, so no message is sent to the brain to limit egg laying, and they continue.

The key hormone is prolactin.

 

[Shadrach]

I haven't found it yet, but in looking I have rediscovered something of relevance to this thread and perhaps of interest to its readers.

It's from Birkhead Bird Sense 2012, the chapter on touch: if eggs are removed as they are laid, some bird species will keep laying daily or thereabouts, until they have laid many more than is normal for that species. In these species, the brood patch plays a vital role in determining how many eggs the female lays. "If the eggs are not removed, touch sensors in the brood patch detect their presence in the nest and then, via a complex hormonal process, allow only the 'right' number of ova to develop in the ovary". But if the eggs are removed, they get no tactile stimulation of the brood patch, so no message is sent to the brain to limit egg laying, and they continue.

The key hormone is prolactin.

That's one of the things I did, not even touch the eggs until a hen had proven broody.

 

[LaurenRitz]

I haven't found it yet, but in looking I have rediscovered something of relevance to this thread and perhaps of interest to its readers.

It's from Birkhead Bird Sense 2012, the chapter on touch: if eggs are removed as they are laid, some bird species will keep laying daily or thereabouts, until they have laid many more than is normal for that species. In these species, the brood patch plays a vital role in determining how many eggs the female lays. "If the eggs are not removed, touch sensors in the brood patch detect their presence in the nest and then, via a complex hormonal process, allow only the 'right' number of ova to develop in the ovary". But if the eggs are removed, they get no tactile stimulation of the brood patch, so no message is sent to the brain to limit egg laying, and they continue.

The key hormone is prolactin.

Interesting. So that should be another question--does the keeper remove all eggs, or leave some in the nest? And how does that affect broodiness?

I remove all eggs, so the only broodies I would get are "broken" in this sense.

 

[LaurenRitz]

Being able to approximate when one is close to going broody would be a big help.

If this pattern exists, I wonder if it resets with the seasonal molt?

 

[Perris]

I still haven't re-found the source I'm looking for, but stumbled across another in the process, and it's also relevant:

The thyroid stimulating hormone receptor (or TSHR) mutated, naturally, and that broke the seasonal nature of reproduction; egg laying was no longer confined to the spring. (It also made hens with the mutation more tolerant of confinement and of overcrowding, which also favoured the human selection of hens with the mutation.) This seems to have happened initially about 1000 AD, and then artificial selection by poultry keepers favoured it going forward. The numbers of eggs laid were still low by modern standards: tallies in Medieval manorial records show the improved lay rates were averaging around 70 to 80 eggs per bird per year, but bit by bit average annual lay rates rose, and got to around 180 eggs per year by the 1930s. Coulthard Fowl Play 2022 chapter 6.

If my memory is correct, the mutation that broke the complete clutch process came along after all this, and is what brought about the jump from those 20th century lay rates to the modern ones of around 300 eggs per year for production strains.

 

[Shadrach]

Indeed. The production breeds came from the highly selected strains that just kept laying, the switch had been killed. But since it was a genetic error (from an evolutionary point of view) naturally enough the same sort of mistake can happen in reverse, and turn it back on, even in the most highly inbred strains.

Not quite. What made the modern production breeds what they are is when we learnt how to keep them ovulating. While breeding over time for hens that laid the most eggs pushed into the 250 plus egg range, the 300 plus eggs a year birds are different. There are only so many eggs in a hen to put it simply. This quantily is fixed at hatch. There is no way of changing it. What has been done is make the hen lay all the eggs she can lay in a continous burst.
I've written this a lot. You can have say 1000 eggs from a hen is approximately 3.5 years or you can have 100 eggs a year over 10 years. You still only get 1000 eggs. Yep, it's simplistic, but it's a good way to look at it.

 

[LaurenRitz]

Did it indicate whether the mutation came from a single bird? I can't see the same mutation popping up in hundreds of carefully maintained heirloom breeds simultaneously.