Offspring larger than their parents

[Hopeful homesteader]

I got my first flock last year, all were 2-3 day old chicks from tractor supply. Their breeds are speckled sussex, blue laced gold wyandottes, blue laced red wyandottes, partridge rock, dark brahma, and blue orpington. The roosters were a speckled sussex and a blue laced red wyandotte. I got rid of the speckled roo because he became human aggressive but I know I fathered at least one.
From my original flock that came from a hatchery, they seem just a tad small for standard sized hens, they are healthy but just didn't grow as large as I expected them to. Now their offspring they hatched and raised from earlier this spring, these pullets are all larger then their mothers already, half just started laying and the other half hasn't yet. Is it common for hatchery birds to just be stunted but their offspring be a little bigger like this? Does anyone have an explanation for how or why this happened?

 

[SmiYa0126]

Are the off springs mixes?

 

[Hopeful homesteader]

Are the off springs mixes?

It's about 50/50 the wyandottes and speckled sussex are full bred but the other half are mixed

 

[Hopeful homesteader]

I also wonder if it could have been diet related. My oldest birds were on a Purina brand the first 5-6 months and it had a lot of cracked corn in it that they would fill up on so I switched to another brand that has no corn or soy, only pellet/crumbles so the offspring have had a more balanced diet, additionally I know they have had significantly more protein compared to the parents because we had tons of grasshoppers these last few months but idk if those things would be enough to have much impact on their growth if any at all.

 

[SmiYa0126]

Ooh, that makes more sense. I was going to ask if you fed them the same food. Yes, the higher protein increases their size. I feed my chicks gamebirds crumble. You should see the size of my cockerel, he's taller than his dad, and he's not even six months yet.

 

[Ridgerunner]

Is it common for hatchery birds to just be stunted but their offspring be a little bigger like this?

No, this is not common.

One thing that controls how big they grow is genetics. Different breeds and just different birds within that breed can grow to different sizes with all else being equal. I see that a lot. People like to think that every bird of a certain breed are identical in all regards. They are not. There can be natural differences in size within a breed. Since the offspring are consistently bigger, that is not the issue in your case.

If you mate a larger bird with a smaller bird the offspring is generally somewhere in between the parents in size. This can be within a breed or across breeds. This might actually be a factor in some of yours but not all. If it is, probably a really small contribution.

What I suspect is how you raised the two groups. The time of year can play a part, what you feed them, how you feed them, and other things like how much exercise they get. They can be stunted if they get too cold, run out of water or are short of food for a while. I don't know what the protein level was in your two different feeds. It sounds like one group foraged for food and the other may not have, at least not at a good time of year. Having a higher protein food when they are young chicks can get them off to a good start.

I did not see you raise them but I suspect the difference in what you fed them, especially in their first few weeks if that was different, is the biggest factor, more than a few grasshoppers later in life. But any or all of it could contribute.

 

[TooCheep]

I'd say two factors are most likely. Hybrid vigor and more protein. Scratch grains provide more carbs/energy, but don't build much bone/muscle. The energy is generally easier to come by than actual nutrition.

Pure breeds are more likely to propagate various defects and recessive characteristics. Hybrids will often grow faster and/or be less likely to continue genetic defects. The downside is that they will have less-predictable characteristics.