caltanissetta

I intended with the way you write the abbreviations.
Because "Breda" comb is caused by a recessive mutation and is written with a lowercase as bd/bd or bdbd (need both alleles to can express).
When is intended NO "Breda" comb which is the original and that is written with a uppercase as Bd+/Bd+ or BdBd .
The "+" indicates also it's NO mutation but it's not necessary to write it but then when used the abbreviations must do attention to the uppercase & lowercase to not give confusion.

When males have the small double (horns) crest (similar to Breda) then the genotype should be Dv/Dv ,r+/r+ ,p+/p+ ,bd/bd which is still combless, but suppressing V-shaped Duplex comb.

The long horned crest must contain for sure 1 allel of Dv the other allel is unsure d+ or Dc but most probably no Breda = Bd+/Bd+.
Their is a "modifying gene(s)" at work to extend, enlarge the hornes an that is supposed to be the "exceptional" single crest gene of the Livorno !

Nothing of this is scientifically proved yet but all is conceptual.