Curious about yolk size

[Margaid]

Hi folks, I wondered if anyone on the forum has any knowledge or theories about what determines the size of egg yolks.

My Welsummers are with a mix of other hens - Favarolles, Cream Legbar, Barnvelder, unknown bantam and a Silkie cross (there are also Houdans but I don't get their eggs very often). The Welsummers lay the biggest eggs and the yolks are bigger than all of the others, but there is very little perceptible difference in the size of the yolk in all the other eggs. Even the bantam egg has a big yolk - great for eating but not so good if you want the white to make meringues.

Because the hens went off lay I had to buy free range eggs from my previous supplier. They are quite big eggs, larger than any from the mixed flock except for the Welsummers, but the yolks are small - a lot smaller than the smallest of ours. They are also very pale. I have no idea what these hens are fed on but I'm very curious as to why there is such a difference. The eggs are sold as free range but I suspect the hens may actually be quite restricted i.e. not ranging over the meadows, hedges and garden as our hens do.

Any ideas?

 

[foxy]

Interesting question Margaid The size of the yolk should be in relation to the size of the chick and of the parent..large chicks need larger yolks to sustain them through the first 48 hours. I guess there will be variables like age and diet. With regard to age, it is always better to hatch from older birds, they lay bigger eggs(bigger yolks..) than pullets therefore the chick would be better off in respect of nutrition as well as the fact that an older bird would be more likely to pass through the benefits of healthy maternal antibodies.
There again there are some large breeds, eg: cochin and orpington which lay a relatively small egg for their stature, however it has been noted that the egg yolks are very much on the large size. This begs the question have certain breeds evolved different nutritional requirements or have more efficient physiologies which have adapted differently to their surroundings? For example Jungle Fowl in their native environment versus a commercial hybrid? Taking this one step further...an ostrich compared to a quail egg? 07
Methinks I need to go out and clean out a few more sheds now!

 

[Marigold]

Interesting question Margaid The size of the yolk should be in relation to the size of the chick and of the parent..large chicks need larger yolks to sustain them through the first 48 hours.This begs the question have certain breeds evolved different nutritional requirements or have more efficient physiologies which have adapted differently to their surroundings? For example Jungle Fowl in their native environment versus a commercial hybrid? Taking this one step further...an ostrich compared to a quail egg?

Quail eggs actually have a very large yolk in relation to their size, relative to the size of the egg it's much bigger than a chicken's yolk, and of course this goes to sustain a really tiny chick. The large yolks make them very pretty when hard boiled and cut open in salads. Apparently they are very nutritious compared with hens eggs as well, with more Omega 3 naturally occurring. Since the yolks are a very deep colour, they make beautiful scrambled eggs and sponge cakes.

I don't know how big the yolk of an ostrich egg would be in relation to its total contents.