The Classroom @ The Coop

Cuckoo Leghorn from White Leghorns

The Classroom @ The Coop: Poultry Breeding/Genetics: Cuckoo Leghorn from White Leghorns

By Hemlock on Saturday, February 16, 2002 - 11:30 pm:

Purdue University has a program where they sell Production White Leghorns to schools and fairs as day 19 eggs. We bought some of these for our county fair. One chick hatched out to have black down. We kept it and it turned out to be a female. She had the color pattern cuckoo, but was essentially the same as any other production white leghorn. When we told the head of Purdue's poultry department, he said he had never seen or heard about a bird like that from their entire program. He also said every so often one would grow up to have little black spots all over it, but never a totally different color. Would her genotype be the same as a White Leghorn, or would she be very different even with the strict breeding program?

By Leee on Sunday, February 17, 2002 - 12:27 am:

Hemlock, Leghorns usually have extended black, E, sex-linked barring (cuckoo), B, silver, S, and dominant white, I. We have gotten some Leghorn females that are only heterozygous with respect to dominant white. The heterozyous pullets are usually the ones that have some black specks or spots coming through the white.

If for some reason, the dominant white does not express, then the white Leghorn becomes a black bird with barring. Dominant white is actually incompletely dominant to the wild-type allele, i+. I am under the impression at this time that a bird that is heterozygous (I / i+) is more likely to experience the lack of expression of the dominant white. We have seen this in our Leghorn strain. What happens is the occasional odd-ball 'sport' appears that is black and barred and is more than likely heterozygous for dominant white but the dominant white didn't express. Breeding experiments can demonstrate that the black barred bird is carrying one gene for dominant white.

Incomplete dominance usually implies the existence of unknown inhibiting factors.

By Rokimoto on Sunday, February 17, 2002 - 10:11 am:

If Purdue sees chicks with black spots some of their birds are heterozygous for dominant white Ii+ (have only one copy of the incompletely dominant gene). If spotted chicks are rare a totally non dominant white i+i+ bird would be even rarer. Two rare spotted birds would have to mate and then only 1/4 of their progeny would be expected to be black barred.

By Leee on Sunday, February 17, 2002 - 04:06 pm:

Rokimoto makes a good point. You would have to know details of the Purdue breeding program to know which is more probable, the accidental breeding of two rare heterozygotes or the occasional non-expression of dominant white in a chick that is a dominant white heterozygote. Our flock has two black barred birds of Leghorn ancestry that we are pretty sure are dominant white heterozygotes from the breeding records. In the same breath, I have been wrong many many times in the past.

If the Purdue researchers hatch a lot of their eggs and have never gotten a black barred bird before, it is surely an extremely rare event. If they accidentally breed some heterozygotes to each other on a regular basis, one might think that they would have seen some black barred progeny.

There are literature references to the incomplete dominance of 'dominant white'.

By Hemlock on Monday, February 18, 2002 - 04:27 pm:

Purdue does a lot of work with their leghorns for egg production and research into "friendly chickens" that won't pick on others in cages. I don't know much about the breeding program other than the spotted chicks are rare too.

By Hemlock on Tuesday, February 19, 2002 - 10:43 pm:

Here is a picture of "Cuckoo"