Contrary to the Canadian "sales pitch" being shared here, Mistral Gris are just a knock off of the Kosher King. It's my understanding that the KosherKing parent lines have been sold to a BC, Canadian hatchery. Those that see the link to Hubbard's Master Gris barred have good eyes, it's obvious that the Kosher King was developed from the Hubbard product. I have 100 approaching harvest time. I will be keeping some as breeders to unlock their pedigree secrets. If anyone wants to see the truth, all they have to do is hatch chicks from Kosher Kings and also from Mistral Gris. When both produce similar diversity, you will see the truth. Sorry call duck, you bought a "sales pitch" hook, line, and sinker.
I've been hatching my own knockoffs of rustic broilers and am most impressed by their potential for backyard/small scale poultry production. Most of my hatching has been from Sasso x431b. The F2 knockoffs are a fantastic dual purpose option because grandma was a meat bird version of a bantam. This means that 1/4 of my knockoffs are bantam sized and can make great meaty layers. They dress out to about 3-3.5 lbs at 12-14 weeks. Start laying at 17-18 weeks. The regular sized siblings dress out to between 5-6.5 lbs with a small number as small as 4 pounds. This is at 12 weeks.
For those wanting premium chicken, harvesting at 12 weeks offers the best balance between flavour and tenderness. I have 30 breeder hens now and despite amazing egg production and hatch rates, I can't grow enough to keep up with demand at our local farmers market. For those that want to grow the best chicken, I highly recomend learning about and following the Label Rouge aproach which is what these rustic broilers were bred for. I follow Label Rouge aproach and most who try my chicken come back declaring that it's the best chicken they have ever had.
One word of caution for those that want to keep their own for egg production and hatching their own. You need to limit their feed intake. I feed mine at dinner time when bringing them in for the night. I feed 35g/kg live weight. There may be better formulas, I'm still learning and sharing what is working at this point.