That is normal in some breeds, could be frostbite (but I doubt it at those temps), or some other condition--like from fighting or bumping their heads on a short doorway.
We have had roosters lose combs to frostbite, and a couple lose toes or feet (you can't MAKE them go into the coop when they can fly into the tree). They lived long lives to die of other causes (but went into the coop easier from then on).
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Yes, that sounds like frostbite. The boys with their big combs and wattles are more prone to this! If I see a rooster with frostbite I know that it is past time to give them supplemental heat, and so I turn the heater in the coop on, to prevent a re-occurance and to protect the laying hens. Anything that causes harm to the hens will decrease their productivity!
Actually, my hens are not laying now because the days are short. That is OK, I try to take gentle good care with the critters that feed me! It seems fair to me. So, the heater will be on and they may be bored but they will be warm!
Sometimes roosters are "dubbed" to remove some of the comb and wattles but I never cared to do that. It sounds as painful as frostbite and not an improvement at all!
Comb color is a sign of the chickens health. Bright red is best, pale means unhealthy, and somewhere inbetween is most common, at only 20-30F they shouldn't be getting frostbite. Unless they're some over-bred bird like a white leghorn rooster that has been bred for only laying genetics.
Slight discoloration may happen as the chicken is adjusting to colder temps, but it isn't frostbite. Really, frostbite hasn't occurred until it's black, before that you can't be sure.
The comb is called a Cornish comb. Makes all the sense in the world to me for a cold climate chicken. My barns are all off-grid, so heating is not an option, nor an interest. I do not see any frostbite with this Cornish comb, ever. With birds that have more traditional combs, I only see frostbite when the temps go below zero Fahrenheit.
I really think that by selecting the right breeds, there is no reason to heat coops in climates that are conducive to good chicken raising. Just like matching seed varietals to our growing season, we should match our livestock breeds to our climates.
We put up some plywood interior sheeting in my dad's little barn in Ontario and blew in cellulose insulation. A good vapor barrier on the warm side is a must. Quite often, I see large barns used to keep too few animals through the winter.
At one point we had a big old barn on a hobby farm that could only support 4 horses, 2 cows and a bunch of chickens and ducks. Dad built a wall to confine the animals to a third of that space. Hay and straw were piled against the cold side. Snow was piled against the outside for both insulation and wind proofing. The birds had a roost above the furry critters. The barn was always much warmer than the winter conditions outside and there was never an attempt to heat it. Animals that have a well insulated home that they share with other warm blooded creatures will be happier and healthier and they won't eat nearly as much as those who are cold.
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