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Curled Toe Paralysis

Hypovitaminosis B2, Riboflavin Deficiency


Riboflavin (vitamin B2) deficiency causes 'curled toe paralysis' in young chicks, which is a common foot abnormality in which the toes curl inward (medially). Riboflavin is an essential, water-soluble vitamin that is required for proper functioning of the nervous system. When chicks do not have enough riboflavin in their bodies, which can result from a riboflavin deficiency in the breeding chickens, and/or by not receiving adequate sources during early growth. Without having enough riboflavin in the body, it causes peripheral nerve damage that leads to degeneration of the sciatic nerve (the nerve which is found along the back of the chick's leg to the foot). This causes the inward curling of the chick's toes, giving the feet a fist-like appearance.

Progression of clinical signs

Chicks that are fed a riboflavin-deficient diet will begin to show signs at about 8 to 14 days following hatch. They will slowly develop progressive symmetrical paresis starting with initial signs of reduced growth rate, weakness and sometimes diarrhea. Affected chicks soon become reluctant to move due to weakness, followed by inward curling of their toes. Without use of the legs, the muscles in the legs will start to atrophy and may eventually extend outward out from underneath the body of the chick.

During advanced stages of this condition, chicks are seen more frequently resting on their hocks, trying to walk as little as possible. It is at this later stage that chicks are at high risk of death from starvation, due to inability to reach food or water sources, or from getting trampled on by other chicks. The condition is still treatable however, as the chick's peripheral nerves are able to rapidly regenerate once riboflavin levels are restored.

Riboflavin requirements

Riboflavin requirements for chickens fluctuate depending on genetics, stage of growth, environmental conditions, level of activity, health status, and other dietary components and synthesis.
Riboflavin (Vitamin B2)
Riboflavin requirements are highest for newly hatched chicks and for chickens used for breeding. The NRC (1994) recommends that poultry species require between riboflavin at 1.8 - 4 mg/kg (0.45 - 1.8 mg/lb) of diet. However, more recently conducted research studies have found that the NRC's recommendation is not sufficient for modern breeds of chickens, breeders, or growing chicks. All chickens should receive a diet with a minimum riboflavin content of 4.4 mg/kg (2.0 mg/lb)

Dietary Sources of Riboflavin

Riboflavin is one of the vitamins most likely to be deficient in poultry feeds. Only a few feed ingredients that are used in poultry feeds that contain enough riboflavin to contribute to the requirements for growth and reproduction.
Riboflavin food sources for chickens
Toxicity concerns
There are no reports of riboflavin toxicity studies in poultry. According to the NRC, most data from studies conducted on rats have found that dietary levels between 10 and 20 times the requirement (possibly 100 times) can be tolerated safely.

Clinical Signs

Toes curling downward and inward
Slow growth
Sitting on hocks
Using wings to walk
Reluctance to stand or walk
Emaciation despite a good appetite


  • History
  • Clinical signs
  • Physical exam
  • Diet evaluation


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chick "intensive care unit") with easy access to water and food.
Vitamin B Complex10 mg/kg administered IM for emergency careK Marx
Supplemental B VitaminsProvide riboflavin-rich feed source or two 100-µg doses of riboflavin, followed by incorporation of an adequate level in the feed
Feed managementReplace current feed with a new bag of quality chick starter feed.
SplintingSplinting the feet might help gradually restore shape and walking ability to feet
HomeopathyFor slow growth administer Alfa alfa, Kali carb, and Jondilla liquid
For birds walking on their hocks and/or diarrhea administer Rhus tox and Calc carb
For curly toes administer Antim cudum and Calc phos


  • Feed chickens a balanced diet consisting of high quality chick starter feed, that was purchased within the past two weeks and that has been properly stored. As feed ages, the nutrients present start to degrade
  • During warm weather, provide supplemental sources of riboflavin


Good if treated promptly

Scientific References


Age Range

Newly hatched chicks are most susceptible to developing curly toes

Risk Factors

  • Wrong feed - Feeding adult chickens intended for breeding, laying hen or poor quality feed
  • Stale feed - Feeding chicks outdated, improperly stored, low quality, or nutrient-deficient starter feed
  • Feeding a corn-soybean meal based diet without providing supplemental riboflavin
  • Warm climates - Environmental temperatures also have an impact on riboflavin requirements, and more is required for chickens raised in a tropical environment or exposed to chronic heat stress.