Dwarfism in bantams?

[seriousbill]

I have a rather odd situation with one of my young Buff Brahma Bantams. It's a 6-week-old pullet, and it is about half the size of its siblings. It is extremely small.

To me, a six-week old bantam is already tiny, but this little female appears to be an ultra-bantam. She's perfectly healthy, though, from what I can see. She eats fine, and she runs around after her Delaware foster mother just fine, but she's a tiny, tiny bird. I know only a little about the size genes that go into creating a bantam, and what I know didn't prepare me for this. I expected all of my birds to be roughly the size of the parents. Furthermore, my understanding is that if there's another dwarfism gene at work, it should involve less than a 50% size reduction. Or is there something I'm missing?

Her parents are unrelated. Could she be a mutation? Or, might I expect more of these tiny ones from the same mating? If I breed her back to her father could I end up with a race of ultra-bantams? I know there's know way to know for certain, but I'm hoping for some informed speculation. Thanks.

Here she is with her normal-sized male clutch-mate:

 

[Guitartists]

There was a pic of a dwarf bird on Feathersite... lemme see if I can find it

 

[horsecrazy]

wow, that is amazing! She looks adorable. Could we have some side shots?

I would totally breed her with the tiniest Brahma roo you can find. You could create a line of micro-bantam Brahmas!!

 

[Guitartists]

I know I saw it there.... but cannot find the breed it was posted in .... if I find it someday again, I will be sure to post

 

[poultrykeeper08]

i had a barred rock hen like that and i was told it was stunted . Meaningit wouldnt grow but somthing was wrong with it

 

[Attack Chicken]

Breed her with a Serama

 

[DTchickens]

i think i'd enjoy a ultra bantam even more

 

[seriousbill]

Quote:
It could be a health issue, but with stunting, there's usually sickliness and failure to thrive. And she doesn't seem to be sickly, just miniature. She eats fine and runs around pretty lively. And, she's survived outdoors so far just fine with no coddling from a standard-sized mama and three much larger brothers. Ya gotta hand it to her, eh?

However, I guess it's possible that there's some underlying health problem that I just can't see. I guess time will tell on that.
To me, right now, this looks like something genetic. And she did look a little different even when she was hatched (she's the small chick at top right):

 

[Guitartists]

Here's some info.... from http://home.ezweb.com.au/~kazballea/genetics/mutations2.html#top

Dwarfing Genes:

There have been four loci identified with dwarfing mutations, one locus with multiple mutation alleles:

* Z
* rg
* adw
* dw, dwM, dwB

* Z "Dominant Sex-linked Dwarfism"– found in Golden Sebrights (Maw 1935, crossed Light Brahma with Gold Sebrights).

* rg "Recessive Sex-linked Dwarfism"– Black Rosecomb Bantams (Godfrey 1953, crossed Barred Plymouth Rock with Black Rosecomb bantams)

* adw "Autosomal Dwarfism"- mutation occurred in Cornell K strain White Leghorns (Cole 1973)

* dw, dwM, dwB "Sex-linked Dwarfism"- closely linked to silver-gold & slow-rapid feathering loci.

-------------------------

- dw Mutation appeared in a New Hampshire flock (Hutt 1959)

- dwB found in Golden Sebright (Custodio & Jaap 1973) (dwB dominant over dw)

dwM found in a meat-type line (Hsu et al 1975). (inheritance relationship with other locus alleles not determined).

Generally large & bantam crosses produced F1 offspring intermediate in size (sometimes closer to bantam size). F2 offspring had the greatest variation in size. An exception was found in a study by Danforth (1929). There was variation between bantam breeds when he crossed a Millefleur Belgian d'Uccle Bantam male with Sebright females. Some F1 progeny were larger than the parents, & in later generations birds both larger and smaller than the parental types were obtained.

I haven't crossed Standard size to bantams, but there is a lot of difference in size between various bantam breeds I have crossed, and sometimes there is obvious variation in sizes within a breed, between lines. Usually the first crosses are intermediate in size, but I've had results similar to Danforth, where F1 offspring were larger than both parent birds (eg Orpington Bantam X Indian Game Bantam, resulting F1 were close to commercial layer size, and unrelated d'Uccle X d'Uccle, some F1 offspring larger than parents, etc). Something that I thought was amiss in “Poultry Breeding and Genetics” was that there was little mention in the chapter of mutations that INCREASE size. Crosses were made between bantam breeds to large Standard size breeds, these much larger than the Red Jungle Fowl –wild type. Obviously mutations that increase size would need to be taken into consideration when determining dwarfing genes.

There is another chapter in the book, dealing with studies on the dw gene, for possible commercial use. Usually these dwarfing genes have little in the way of deleterious effects to general health (sometimes heath gains), but of course there are few production issues, eg reduced egg size, body weights, etc (tend to be more efficient with feed consumption to production outputs though).​

 

[Chickndaddy]

The dwarf bird on Feathersite was a Cuckoo Marans hen. I remember her from the auction they put up on eggbid several years ago. That picture is the one from her auction.

http://www.feathersite.com/Poultry/CGK/Marans/BRKMarans.html

She is eight pictures from the bottom.