Nankins are one of a small number of breeds that have two varieties that can be kept and bred together, but shown in seperate classes. Leghorns and Rhode Island Red bantams are the most common of this group. This can lead to some confusion in judging in poultry shows because the after the best of variety for each is selected, the two varieties should be judged against each other so there is only one best and reserve of breed. Then only this bird goes on to compete for class champion in either the SCCL or RCCL (Single/Rose Comb Clean Legged). The reserve of breed can be from the same variety, age, and/or gender as the best of breed, but it does not have to be.
My first trio of Nankins were of Rose Combs, and the roses have always been my favorite of the two varieties. However, after a few years, I did start hatching and breeding singles as well. I just considered myself fortunate to raise a breed where the two varieties are so similiar and can be kept and bred together but shown in seperate classes. However, when I first started breeding single combs, I tried my best to follow the advise of older breeders and only breed rose-to-rose and single-to-single to maintain comb quality. Since the rose comb gene is dominant over single comb, I would often have single comb chicks come from two rose comb parents. I just moved these into the single comb part of my breeding program and kept going.
After a few years, I decided to try deliberately crossing the two varieties. I tried putting my darkest SC cock with a RC hen with good earlobes to balance the relative strengths and weaknesses of the two groups. The first year was a disappointment. The hen did hatch 15 chicks in two clutches, but her lighter feather color influenced the chicks more than I hoped. Disappointed, the next year I decided to give it one more go, but this time the rose comb pullets I put with him were two of his daughters from the previous year. I normally don’t make breeding pens with birds this closely related, but I thought I could try it once as I hoped the girls were carrying one dose of his dark color, even if they didn’t show much of it. That time I was very successful. The chicks, especially a pair of RC cockerels, were beautiful. They had the dark color of the single combs, but the comb and earlobes from the rose combs. The next spring, my favorite brothers were put in with my normal RC breeding pens where they gave me a SC son as beautiful as they were among other chicks.
After I started mixing the rose and single combed birds in my breeding pens, I noticed that the comb quality did not seem to degrade as I heard it would. Admittly, the quality of my rose combs was not high to start with as I am still battling the “spike that looks like a blade” problem. Having not seen any issues, I decided not to worry about comb type so much when setting up my breeding pens. I do still breed single-to-single and rose-to-rose most of the time, but that is for other reasons. Since I prefer rose combs, I try to keep more of them than the singles, roughly 2:1. This can be a bit challenging as I seem to hatch as many or more singles than rose combs although this can vary a bit from year to year.
This year for Christmas I recieved “Genetics of the Chicken Extremes: The Basics” by Sigrid Van Dort. I haven’t had the chance to really read it, but I did flip through it earlier. It has several sections I want to examine further later including sections on the Polish skull and various lethel genes, but the one section I did read through as I was flipping was about the rose comb. I already knew that the rose comb gene was dominant to the single comb and could be combined with the pea comb to form the walnut, but there was alot more information there!
Much of the section focused on fertility problems related to the rose comb dating back to research published in 1963. This book claims that each copy of the rose comb gene is linked to a fertility penalty in males. In females comb type does not matter to fertility, and it even claims that males prefer rose comb hens over pea and single comb hens despite them having a more aggresive attitude (apparently they don’t like a “sneak attack” mating style). I wish this book gave more details about this research such as the breeds, age, numbers and breeding setup used, as well as, some discussion of how these factors and individual bird personality could affect the results. If this was only done once, with one breed, I would be very interested in knowing if it was ever duplicated with other breeds later. I couldn’t help but wonder as I read this if this was an actual connection with the rose comb gene, or linkage drag with something else in the genetic background of the birds being used.
The big conclusion of the study was that each copy of pea and rose comb gene reduces fertility so that that from most to least fertile it goes Single Comb –> Rose/Pea Comb carrying a single comb gene –> Rose/Pea Comb –> Walnut Comb. Apparently single combs have a higher percentage of dead sperm, but rose combs sperm dies faster, and has a tendency to have a more crooked swim path. The researchers tried artifically inserting the sperm deep into the hens’ reproductive system and found that the fertility issues disappeared. This indicates the problems are physical (not genetic like lethal genes) and located solely on the male side.
I thought that this was all very interesting. When you put these facts together, you find that single and “half-single” roosters are likely to be more successful at passing their genes along than “pure rose” males. This might explain some of the inbalance in comb type of my chicks. I had thought that the extra single combs came from a high freqency of the single comb gene hiding in my rose comb breeding pens, but I guess it could also come from mating and physiological differences as well.
I need to look into this more, and possibly test it in my own birds, but if this is true, then I need to adjust my breeding strategy if I want to increase my proportion of rose:single comb chicks.
Thoughts From a Wandering Hoosier 