Maternal vs Paternal Heritability

[SourRoses]

You see most chromosomes chickens have are the normal x shape.
But sex chromosomes are special. Females have W and Z and males have two Zs. Traits that are on the Z chromosome are only inherited from the father on females. Males get a Z from each parent. These are sex linked genes.
Most genes aren’t sex linked but quite a few are. Some quantitive traits without assigned genes seem to have it where one parent has more effect than the other in determining the outcome.
There is a sex linked gene associated with dark shell color

Thank you, this is very interesting!

 

[3KillerBs]

Another I remember had to do with commercial laying operations, that they choose breeding roosters based on the laying traits of his mother + grandmother, in order to arrange the most effectual improvement.

That's normal breeding practice when selecting for a trait that only shows in one sex.

Cows give milk and hens lay eggs. Bulls don't give milk and roosters don't lay eggs. Therefore, if you want increased production for milk or eggs you use the males' mothers and grandmothers as proxy in the expectation that males whose female relatives had high production will carry the genes for high production even though they themselves don't produce.

You could do it in reverse -- say selecting for really glorious sickle feathers in the roosters. You'd use hens whose fathers and grandfathers had really glorious sickle feathers since hens don't grow sickles.

You select more critically for traits in the male because your chicks may have 10 different mothers but only one father.

 

[nicalandia]

I have read that egg color is passed more from the rooster.
Is the same true for egg size?

Egg Color, Egg Size, Egg proficiency and Broody traits are Polygenic traits(multiple genes play a factor) many of those genes are located on the sex linked chormosome Z.

Somewhere else (less verified) someone stated that feather type is more influenced by the hen. True/False?

Feather Type, like soft/hard feather, Silkie, Frizzle are Autosomal in nature and both parents contribute to the expression.

What about body size? Egg size? Leg color? Comb type? Other traits?

Body size, Body shape are Autosomal and both parents contribute. Dark vs Light shank is a sex linked trait so a Dark Shank rooster will give it's dark shanks to it's F1 female offspring.

Since roosters are passing on more genes in general (right?) would they be a better choice for almost all pairings where you were trying to breed in certain traits? What traits might you look to use a hen for?

This is a very accurate assumption.

What traits might you look to use a hen for?

That will depend on the end goal of the breeding project. Don't breed a Leghorn to a Silkie hen if your end goal is max amount of eggs or meat production.

 

[Amer]

While it’s true roosters pass on more genes to their daughters, many breeders find that for whatever reason, hens have more effect on the offspring’s quality. I don’t think I believe it though.
A breeder of of bantam Buckeyes found that hens will have more effect on the type and comb of the offspring while cocks will tend to effect size and coloring. Why this is true or whether this is purely coincidental I don’t know. I think it’s best to say both parents affect offspring equally, though sometimes differently.

 

[nicalandia]

I think it’s best to say both parents effect offspring equally, though sometimes differently.

From a purely scientific standpoint/Objectivity. I can't agree with that point if I view

 

[Amer]

From a purely scientific standpoint/Objectivity. I can't agree with that point if I view

I suppose so.
Let me rephrase.
While one parent may pass on more genetics than the other, both are equally important when it comes to selection for traits, as the higher quality of each parent means higher quality offspring. In the same way, both parents need to have the genes you want unless you are focusing on a single sex linked gene.
Many overlook the importance of the female in breeding and will always post pictures of males. Especially in game birds. In reality, both sexes need just as much care in selection. People will fall into the trap of producing mediocre birds because they breed multiple females of varying quality with an excellent male, thinking he will fix their problems. People rarely look at the combs of females.
Males and females must balance their traits out, a weak point on the female must be a strong point on the male, and vice versa.

 

[DarJones]

On a pure one on one basis, rooster and hen contribute pretty much equally to the offspring. But when I have 3 roosters and 21 hens, the rooster is far more important to flock traits.

My normal routine is to choose the best rooster I have and cull half of the hens. As an example, I have a round of 18 chicks of which 3 meet almost all needed traits. One is male and two are female. I will probably keep all three for breeding after I DNA test them for the blue egg gene. Of the remaining 15 chicks, 7 have odd color combinations so I will either slaughter or give them away for egg laying. That leaves 8 chicks of which I will keep the hens and slaughter the males. After the hens are old enough to lay, I will cull any that lay brown eggs.

What does the above highlight? Selection for breeding stock should be done in stages with early culling of chicks that don't meet requirements followed by culling all the way through to the point where they reproduce. BUT! Be very very picky with your roosters.