Egg size and genetic potential

[Mike Gilbert]

Here is an interesting post from an Australian expert on the Classroom at the Coop Genetics Forum today:

"You're forgetting what D. Caveny & R. Okimoto said, ie you are excluding genetics potential again. A pullet laid egg has the same genetic potential as when the hen lays an egg when 2 years old. The pullet egg will hatch as a smaller chick, the mature hen's egg will hatch as a larger chick, but both chicks will reach the same adult size. So no, a bigger egg yolk does not mean bigger end weight, when comparing apples with apples (given the same genetics).

I look at it this way. A budgie lays a proportional size egg to it's adult body size - no disadvantage laying this tiny egg to the viability of the chicks & reaching fast maturity. And I don't see it as a disadvantage to the Red Jungle fowl laying a small egg, in fact it can be a disadvantage to lay a larger egg (proportional to adult body size - eg R. Okimoto's example - prolapse). Which ironically is how my brother selects cattle for beef production - a breed with average smaller calf birth size (& cow with good hindquarters/pelvis for birthing, less birthing problems for 1st time heifer-cows) & very fast sexual maturity (he has less deaths for 1st time mothers/calves & more calves produced -earlier sexual maturity, plus quick growth for weener market).

Sounds like those German forum breeders are multipliers, not exhibition breeders (no exhibition breeder is going to get rid of quality older breeders so lightly).

But also it sounds counter-intuitive to me. If someone wants to multiple bird numbers &/or generations quickly season after season, the pullets that lay the earliest, & viable young mature the earliest for next generation, are going to be passing on these genetics generation after generation. So there is some natural selection going on for early maturity."

[John W Blehm]

Mike, you must have been posting that here while I made the reply on the Coop...
 

Originally Posted By: KazJaps

You're forgetting what D. Caveny & R. Okimoto said, ie you are excluding genetics potential again. A pullet laid egg has the same genetic potential as when the hen lays an egg when 2 years old. The pullet egg will hatch as a smaller chick, the mature hen's egg will hatch as a larger chick, but both chicks will reach the same adult size. So no, a bigger egg yolk does not mean bigger end weight, when comparing apples with apples (given the same genetics).

That backs up my assumption and what I told others over the years, not just with pullet vs. hen eggs but crossing bantams and large fowl.

And here is a post of mine from several years ago...

Egg size   Â« Reply #1 on: March 13, 2007, 08:33:34 PM »

a hen that is the proper size lays a small egg

For the most part bigger birds lay bigger eggs, but there seems to still be a range of egg size.  Even with bantams I have some hens/pullets that lay pretty big eggs for bantams.  Some of the commercial egg laying chickens that lay extra large eggs are not extra large - large fowl.  I think we need to breed birds that are to the "standard" by weight according to a scale, not just by eye.  I think you will find most silver and wheaten Ameraucana LF are under size. 
The Standard doesn't say what size the eggs should be.  The eggs have to be big enough or small enough to produce "standard" size chickens - both LF and bantams.  I would strive for chickens of the proper size first.  I think that by selective breeding for bird size that proper egg size will follow.  I wouldn't cull chicks because of the size of the egg they came from, but only breed from the ones that grow up to "standard" size.  If none are to size, breed from the ones that are closest.  And do the same every year.  Sometimes a cross is needed to bring in genes that are needed to accomplish the goal.

[Mike Gilbert]

 I guess great minds think alike?   

[Suki]

I don't agree.  A bird cannot pass on what is not yet expressed in their physiology and as it ages different diseases and traits form.  Genetic material is not static, but evolutionary and enviromental, it seems everyone here is arguing for the former.

[John W Blehm]

I don't agree.  A bird cannot pass on what is not yet expressed in their physiology and as it ages different diseases and traits form.  Genetic material is not static, but evolutionary and enviromental, it seems everyone here is arguing for the former.

The advice I heard from more than one source years ago was that if you are crossing LF and bantam you should use the hen of the size you are breeding toward.  Their logic was that a chick from a smaller egg would be small and mature closer to bantam size and larger eggs produce larger chicks that mature into bigger chickens. 
There have been four loci identified with dwarfing mutations, one locus with multiple mutation alleles:
A few of these dwarfing genes are sex-linked. 
Dwarf dw Recessive. Males are reduced in size by about 43%, females by 26-32%. Multiple alleles have been proposed. dw is responsible for some beneficial effects. dw homozygotes are more resistant to Marek's Disease and spirochetosis, fewer laying accidents, more aggressive immune response. Abnormal eggs are suppressed (soft-shelled, double yolks). Dwarfism, dw, does not effect mortality but does postpone the onset of lay in pullets up to two weeks. Although egg number and mass are slightly decreased by dw, feed efficiency (feed consumption per egg layed) in laying stocks is usually increased 13-25%.
Because of that I prefer to use the male of the size I'm breeding toward over a female of the other size.  The chick's size at hatch will be determined by the female's egg size.  Even though they will mature to an intermediate size the pullets should favor the male's breed size and be good candidates to breed back to him.

I'm making an outcross between LF brown red and LF black.  Brown reds are on the small side.  I believe there is a dwarfing gene floating around in their lines.  I'm using medium sized brown red males over a large black pullet, but know wish I had a brown red pullet to put under my large black cockerel.  I believe the size issue would improve quicker that way.  Since it is too late to change, I will breed the F1 birds among themselves selecting for size.

[Suki]

Because of that I prefer to use the male of the size I'm breeding toward over a female of the other size.  The chick's size at hatch will be determined by the female's egg size.  Even though they will mature to an intermediate size the pullets should favor the male's breed size and be good candidates to breed back to him.

Shouldn't it be that the males will favor the female size and maybe intermediate while the pullets be smaller then?

[Tailfeathers]

I don't agree.  A bird cannot pass on what is not yet expressed in their physiology and as it ages different diseases and traits form.  Genetic material is not static, but evolutionary and enviromental, it seems everyone here is arguing for the former.

I disagree.  A bird can and does most certainly pass on what is not yet expressed in their physiology.  Color being one of the most obvious traits.  Recessive genes being another.  Diseases and the antibodies that stem from them may or may not be passed on.

That said, I'm a proponent of breeding birds that are 2yrs old or older and not breeding pullets unless absolutely necessary primarily because of the disease and vigor factors.  Pullets simply may not have been alive long enough to demonstrate their vigor and their resistance to diseases.

I first considered this issue several years ago after reading Kenny Troiano write about it in the PP.  I know he brought up other factors besides disease and vigor that made sense but I can't remember now what they were.   The thing that matters to me is that it just seems to make sense you're gonna know a whole lot more about a bird at 2yrs old than at 6mos old.

[Mike Gilbert]

Other reasons for waiting to breed hens until they are two years old are several I can think of offhand.   Sustained egg production is one.  Tail and wing color in wheatens and blue wheatens is another.   Maintaining decent feather conditioning could be another.    I know my buff Chantecler females lose many of their back feathers over a breeding season, while the partridge variety does not.   Edited to add:   Shell quality is sometimes less than optimum in older hens, so that is another thing to be considered. 

[Suki]

from the USDA circular 1917


A hen does not need to be culled on account of her age. If a hen lays well one year, she should be kept for another as a breeder. The older she is and the more culling she survives, the better, for then she has proved that she has the vitality to stand up under long-continued laying, and hence is many times more valuable as a breeder than is a pullet or a yearling hen. A flock of persistent layers should be kept each year for breeding; the older they are, the better

[Suki]

 In this test,, the eggs laid by hens three years old were more satisfactory for hatching than those laid by the young pullets for the chicks were heavier, and much more vigorous than the chickens hatched from pullet eggs, and apparently somewhat more vigorous than the chicks hatched from eggs laid by hens two years old. There was not much difference in the hatchability of the eggs.

----Prof Horace Atwood, Morgantown WV, 1909 from a paper given at the Poultry Breeders Conf in
Columbia MO

[John W Blehm]

Sue,

Both of those are about 100 years old.  I understand some things never change and what was true then can still be true today, but also keep in mind that a lot has changed.  Most breeds are quite different today than they were then, incubation has made huge advances, feed has improved and so on.  All of this can make a difference and should be considered when reading old papers. 
As I'm working on our latest Handbook I know that several articles from our previous Handbooks, over the past 34 years, would need to be revised/updated before being reprinted.

[Suki]

Sue,

Both of those are about 100 years old. 

Yes i know that.  Take it as you wish.  I haven't seen much done lately on that topic btw, except anecdotally so that's all I have.

[Shari Nees]

I decided to sell of my nice Bantam white Am's as I could not find a really good white AM rooster,  I let them run in the main flock, until sold.  Collected the eggs and decided to hatch out a couple.
The Bantam AMs were in with a Legbar.  The resulting chicks hatched out bantam sized, but grew about 1/3 bigger than my d'Anvers of the same age. d'Anver's are quite small.
Time will tell if they get any bigger.

Also agree on waiting until the pullets are older before hatching out eggs from them.  Less problems that way.