Last year 2013, nearly 1/2 of my dom chicks had single combs. This year none. And yes, they are all Dominiques. The single comb gene is in my flock, which is OK, as single comb cockerels are delicious. They are all Dominiques, though I don't use any single combed birds in my breeding program. Sometimes it just happens. The "Single comb=Barred Rock" concept was started after the two breeds were defined and split in the APA standards in the 1870's. Before that there were a lot of single combed Dominiques, based on type and color/pattern.
As far as measuring egg production, the reason I use the calendar year method is that for me, its easier. I'm not so concerned with an individual hen's lay factor, but with that ot the whole flock. For me, it gives me a better overall judge of flock production, and where my particular line is going. This year the lay factors are slightly lower, mostly due to the fact that I didn't keep many pullets from last year, and my older hens are dropping off a little in production, which brings the overall numbers down a bit. That's OK. Again, I am measuring the flock as a whole, and don't want just first or second year layers. As the year progresses, and this year's pullets start laying in earnest, the overall flock egg numbers will come up a bit. Eventually I would like to have a line that lays just under 200 eggs per year per hen, but not more than that. That would be an overall lay factor of .548 for the year. Just a goal at this point.
My dom eggs average 2.0 for mature hens. That's barely in the "large" category. A couple of them lay a larger egg, but they aren't the norm. One of them my daughters named Patty McFatty....... LOL
I will start looking for a coorelation between high egg numbers/larger eggs and thinner shells. Interesting thought.
Some of the eggs are thinner shelled than the others. Not sure why. they have ground up shell free choice at all times, plus regular layer feed. Some have very thick hard shells. Hopefully the shell thickness will even out for the flock as a whole...
Fun projects!