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Frostbite

Chickens are susceptible to frostbite, which is a common welfare problem in backyard chickens due to exposure to cold weather. The majority of frostbite cases involve the unfeathered parts of the bird's body---comb, wattles, toes, feet, and legs.

Birds do possess the ability to adapt to colder environments faster then mammals. This is related to something referred to as a hunting reflex, which is the ability to preserve tissue viability of their extremities through regular, intermittent vasodilation. However, this is only for a short durations. When temperatures continue to drop, this vasodilation stops, and tissue damage occurs.

Frostbite is a localized tissue injury which develops as both direct freezing injury and ischemia resulting from impaired vascular supply. It occurs upon exposure to temperatures below the freezing point of the tissue (typically −0.55°C, but can occur as high as 2°C) for a sustained period of time. Once the fluid in the bird's body part (tissue) freezes, it results in a loss of blood supply and deprives the cells of oxygen. Without oxygen, the cells die, along with the tissue.

Stages of frostbite


Frostbite severity can range from complete resolution without significant secondary complications, to gangrene, sloughing, and amputation of extremities following frostbite. The severity depends on factors such as absolute temperature, wind chill, duration of exposure, wet/dry cold, immersion, chicken breed, age, and overall health. In mild cases,
Frostbite - chicken feet
  • First degree – Often referred to as frostnip. Simply freezes the surface level of skin. The skin of the comb or wattles will turn an off-white, pale color. If the feet and legs are affected, they will appear slightly reddened.
  • Second degree – If freezing continues, the skin may completely freeze and harden, but the deep tissues are not affected and remain normal.
  • Third and fourth degrees - In severe frostbite, this stage affects all layers of skin and the tissues beneath. As the affected tissue dries, it will turn black (as a result of gangrene), and slowly mummify and fall away from the surrounding healthy tissue---at what is known as the line of demarcation. The line of demarcation in birds may take 3 to 6 weeks to develop.
Frostbite -Comb and wattle
When birds develop frostbite, the long-term effects seen in the surviving tissue includes increases susceptibility to cold reinjury, sensory loss, decreased circulation, and osteoarthritis. In combs and wattles, this may appear as a bluish or purplish color.

Clinical Signs

Discoloration or blackening of tips or edges of comb and/or wattles
Reddening of feet or toes
Cold and/or hard skin
Blackened areas of toes
Swelling of comb, wattles and/or toes
Blood-filled blisters

Diagnosis

  • History
  • Clinical signs
  • Physical exam

Treatment

NameSummary
If tissue is still frozenRapidly rewarm in a warm (body temperature, 104-108 °F (40-42°C)) water bath.
DO NOT use direct heat (such as a heat lamp, hair dryer, heating pads, etc,) to rewarm the affected area.
DO NOT rub, massage, shake, or otherwise apply any physical force to frostbitten tissues, as it can cause more damage to the affected area.
DO NOT disturb any blisters or skin that has blackened.
DO NOT let chickens walk on frostbitten feet or toes, as walking will increase the damage. Restrict movement through the use of a sling-type restraint, splinting, or wrapping.
DO NOT trim the blackened areas. These areas actually protect the remaining, living tissue. Removing the blackened areas can expose the living tissue underneath and increase the risk of infection.
DO NOT put the chicken back outside. If there is potential for refreezing of an area, do not attempt to thaw, as thawing followed by refreezing can cause even more extensive damage to the area. Place the chicken in supportive care, in a warm environment.
Supportive careOnce the affected tissue is warmed up, gentle wrap the affected area (not too tightly!), if multiple toes are involved, make sure to wrap each toe separately. After wrapping, place the chicken in a quiet, comfortable recovery area that does does not run the risk of re-exposing them to the cold. Make an appointment to take them to see your veterinarian. Depending on the severity they may require hospitalization. In most cases, pain medication is indicated since frostbite is extremely painful. Prophylactic antibiotics may be indicated to help prevent secondary infections.
Streptokinase treatment and rapid rewarmingResulted in reduced tissue damage and was most beneficial when given within 12 h of freezing and was still effective even when treatment was delayed up to 48 h

Support

Prevention

  • Provide your chickens protection from cold temperatures by winterizing coop (insulate & prevent cold drafts), keeping bedding dry, and ensuring proper ventilation to prevent moisture build up
  • Cover combs and wattles with petroleum jelly - which helps with mild freezing
  • Perform a physical exam on each chicken, especially ones with large combs and wattles, after cold nights for signs of frostbite
  • If you live in colder climates, choose chicken breeds which are more cold-hardy and less prone to effects of frostbite
  • Monitor humidity levels in the coop with wireless weather station sensors.

Scientific References

Good Overviews

Blogs

Age Range

Adult roosters with large combs are more prone to frostbite

Risk Factors

  • Roosters and/or large comb breeds - Frostbite is most common in roosters, as they typically have larger combs and wattles, however any hen with a large comb can be vulnerable.
  • Dehydration - Keep chickens hydrated, as dehydration can increase the risk of developing frostbite. Make sure chickens have access to water that is not frozen, through the use of water heaters.
  • Poor ventilation (air flow) - Chickens that are housed in uninsulated, unheated, poorly ventilated coops have an increased risk of frostbite. This is because chickens tend to generate alot of moisture, from their droppings, and through breathing, thus increasing the humidity level. When temperatures drop below freezing, coupled with the humidity (that produces moisture or water on the areas of the body with the least amount of blood circulating through them, i.e. combs, wattles, and toes), it leads to frostbite.
  • Living in high altitude areas - Chickens living at higher elevations have reduced oxygen supplied to the capillaries.
  • Pre-existing health conditions - Chickens with certain health conditions, such as metabolic disorders or atherosclerosis which may have reduced body circulation.
  • No access to shelter - Any chickens that are left outside without shelter.
  • Wind/Rain/Snow - The presence of wind, rain and/or snow. Feather legged chicken breeds are particularly susceptible.

Case Stories

Seasonality

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