Thank you so much for the info! The article confirms that Icelandics have the R1 gene thought to be causing low infertility, meaning it's indeed something I need to consider when breeding Icelandics.That is pretty much what I've read, too, about homozygous rose comb roosters being less fertile than others. I've read that the sperm does not live as long after mating (so the rooster needs to mate with each hen more often), and I've read that they tend to mate less often. I have no personal experience to back up any of this.
The obvious workaround is to have fewer hens per rooster, so it is easier for him to mate with them all frequently.
I've also read that there are two different rosecomb alleles, one with that effect on fertility and one with no problems. If you could breed a flock with the other rosecomb allele, you wouldn't have trouble with fertility-- but there is the trouble of getting the right allele in the first place, and recognizing when you have it.
A study that talks about the matter:
https://pmc.ncbi.nlm.nih.gov/articles/PMC3386170/
"The Rose-comb Mutation in Chickens Constitutes a Structural Rearrangement Causing Both Altered Comb Morphology and Defective Sperm Motility"
Published in 2012
(Not easy reading, but it is the most authoritative source I can easily find. It does contain a table of what breeds were found to have which rosecomb alleles. I don't know if any of them would be easy for you to get, or whether they would even be welcome in your breeding program because they might bring other traits you don't want.)
For your flock, as a practical first step, I would probably give the rooster more time before you make any drastic changes. He might improve with time and practice.
If that doesn't work, I might split the flock so he is with just a few hens, the ones you most want to hatch eggs from. If you want to hatch eggs from them all, maybe give him one group, get a batch of their eggs developing nicely in the incubator, and then put the next group of hens with the rooster. You could work your way through the whole flock in small clumps.
And most of that was probably stuff you already read elsewhere, or thought of for yourself before I got around to typing it
I'm going to focus the breeding on combs, to prevent frostbite in winter. For some reason many Icelandic chickens in my country have huge single-combs, with I find terribly impractical in a cold-weather country! I've never bred specifically for combs before, so it's all new to me. I'm thankful I found the information about rosecombs and fertility here on BYC, or I'd probably be at loss of what was happening if I kept breeding only rosecombs.
I'm looking into the genetics of comb size too, as small single/v/butterfly-combs (haven't found pea-combed Icelandics yet) would also do well, on hens at least, when it comes to frostbite.
I'm probably not keeping the rooster another season, as I'm going to have a lot of new blood this year, but it would be a practical "experiment" to incubate some eggs from him later this year (oh no more chicks how awful
)So I think the best solution long-term is to have a rosecombed rooster and other-combed hens. That way I'll never get an RR rooster.
Oooh that's interesting! And it will be interesting to see how long it lasts, if they go back to low fertility when you have RR roosters again.
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