Walnut comb phenotype associated with reduced fertility?

[centrarchid]

I am starting year four in a long-term project to develop what is to be called the Missouri Dominique. It is a composite of American Dominique, American Game and California grey. Now that backcrossing is stopped, subsequent generations will be just over 1/2 American Dominique, about 1/3 American Game with the balance being California grey. All birds are carry at least one copy of the rose comb allele and about 1/3 carry the pea comb allele (coming from the American Game side) at their respective loci where the alternative allele for each loci are for the wild-type single comb. Male birds with both rose comb and peacomb alleles have been performing very well with respect to growth and type probably based on chance. After two winters of suffering my keep the walnut phenotype has done very well showing no signs of frostbite related injuries and their fertility has been very good. Rose comb is good but not as good. Based on parentage all birds in breeding pens are currently heterozygous at both loci. I am thinking very seriously selecting so birds are homozygous at both loci needed to code for walnut comb. Not only will the phenotype then breed true, it will hopefully also help further tighten comb and wattles reducing concern about frostbite.

Is the walnut phenotype associated with reduced fertility when birds are homozygous for the trait?

 

[centrarchid]

I am guessing the walnut calm has not been considered with respect to fertility?

 

[Old Rando]

I have read of rose comb being associated with a reduction in fertility but I have never read of reduced fertility being associated with walnut comb. But it is not anything I have made any effort to investigate.

 

[Henk69]

Walnut comb is the combination of peacomb and rosecomb, so yes there could be a fertility issue.

 

[centrarchid]

Walnut comb is the combination of peacomb and rosecomb, so yes there could be a fertility issue.

Thanks Henk,

Among my pure rosecomb birds, some exhibit reduced hatch rate, particularly when ambient temperatures are high. I am not certain if it is due to actual male fertility or failure during embryonic development. I am very much concerned the peacomb would be additive to that.

 

[Henk69]

The rosecomb issue is fertility only, afaik.

 

[centrarchid]

The rosecomb issue is fertility only, afaik.

As in sperm motility, count or viability? I have not seen original literature regarding issue. To partially compensate hens producing hatching eggs get continuous exposure to roosters while hens not bred to rose comb birds get exposure every third day and good hatch still realized even with 5 days between exposures.

 

[Henk69]

The main problem is that when a rooster is heterozygous rosecomb, the single comb sperm cells are superior.

 

[centrarchid]

The main problem is that when a rooster is heterozygous rosecomb, the single comb sperm cells are superior.

My goal is to realize homozygous rosecomb allele in the walnutcomb birds. I did not realize the rosecomb allele impacted the phenotype of the sperm carrying it. Once the rosecomb genotype is fixed, no singlecomb heterozygotes or homozygotes will be allowed to compete with the otherwise lower fertility rosecomb birds.

 

[Henk69]

That would work.