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Curly Toe Paralysis

Other Names: Curled-toe Paralysis

Curly toe paralysis presents as inward curling of the toes on the chicken's feet, which impairs their ability to walk. Affected birds may be seen walking or resting on their hocks. The condition occurs when the sciatic nerves are damaged. The two most common causes of this condition in chicks are Marek's disease and riboflavin (Vitamin B2) deficiency.

Riboflavin is one of the vitamins most likely to be deficient in commercial chicken feeds. Only a few feedstuffs fed to chickens contain enough riboflavin to meet the requirements of young growing chicks or breeding hens producing eggs to be hatched. Feeds which utilize corn or soybean meal as the primary ingredient are more likely to be deficient in riboflavin. Riboflavin is easily destroyed upon exposure to ultraviolet (UV) rays or sunlight. Therefore if chickens are fed outside the portion of the feed exposed to light won't contain much riboflavin.

Chicks with curly toe paralysis will slowly develop progressive symmetrical paresis and weakness. Affected chicks soon become reluctant to move, followed by intermittent flexing and inward curling of 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.

Nutritional Riboflavin Requirements

Nutritional 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 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 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). Recommended riboflavin levels from DSM Nutrition are as follows:

Age/Life Stage	mg/kg
Newly Hatched Chicks (0 - 10 wks)	6 to 7
Young & Growing (10 - 20 wks)	5 to 6
Laying hens (Actively laying eggs)	5 to 7
Breeders (20 wks & older)*	10 to 12
Broiler/'Meat' Breed Chicks (0-18 wks)	6 to 8
Broiler/'Meat' Breeds* (19 wks & older)	12 to 16

Clinical Signs

Toes curling inward

Diagnosis

History
Clinical signs
Physical exam
Diet evaluation

Reported Cases

Case 1: Curly toe paralysis in a Chickens Curled-toe paralysis due to Riboflavin (Vitamin B2) deficiency was attributed as the cause of neurological signs such as paralysis in 10-day-old white broiler chicks. Approximately one percent of the chicks in a flock of 25,000 exhibited signs. Microscopically the peripheral nerves had demyelination and mild inflammation. These chicks did not exhibit curled toes probably due to the acute stage of the disease. Ref

Case 2: Riboflavin deficiency in a Chicks Riboflavin (vitamin B2) deficiency in young chickens produces a demyelinating peripheral neuropathy. In this study, day-old broiler meat chickens were fed a riboflavin-deficient diet (1.8 mg/kg) and killed on posthatch days 6, 11, 16, 21, and 31, while control chickens were given a conventional diet containing 5.0 mg/kg riboflavin. Pathologic changes were found in sciatic, cervical, and lumbar spinal nerves of riboflavin-deficient chickens from day 11 onwards, characterized by endoneurial oedema, hypertrophic Schwann cells, tomacula (redundant myelin swellings), demyelination/remyelination, lipid deposition, and fibroblastic onion bulb formation. Similar changes were also found in large and medium intramuscular nerves, although they were less severe in the latter. However, by contrast, ventral and dorsal spinal nerve roots, distal intramuscular nerves, and subcutaneous nerves were normal at all time points examined. These findings demonstrate, for the first time, that riboflavin deficiency in young, rapidly growing chickens produces selective injury to peripheral nerve trunks, with relative sparing of spinal nerve roots and distal nerve branches to muscle and skin. These novel findings suggest that the response of Schwann cells in peripheral nerves with riboflavin deficiency differs because either there are subsets of these cells in, or there is variability in access of nutrients to, different sites within the nerves. Ref

Treatment

Name	Summary
Support	Provide additional support to make sure the chick has easier access to feed and water, aren't getting picked on by the other birds, and are in a location where there is zero risk of predator attacks. Help maintain or improve their quality of life.
Assist with mobility	Purchase dog shoes or make a customized corrective shoe.
Vitamin C	Research studies demonstrated that supplemental vitamin C can help nerves regenerate. The dose for chickens is 250 mg/kg body weight.	Li et al., 2019; F Rafiee et al., 2016

Support

Prevention

Feed newly hatched chicks a fresh bag of starter chicken feed (not feed that has been stored for longer than 2 months), with additional riboflavin food sources during the two weeks of life.
During warm weather, provide supplemental sources of riboflavin.
Store feed in a sealed plastic container located away from direct sunlight.
Fermenting feed significantly increases the proportion of riboflavin present.

Scientific References

Rebecca Duerr, DVM MPVM. Splinting Avian Fractures International Bird Rescue Research Center (2020)
UC Davis California Animal Health and Food Safety Laboratory System. CAHFS Connection Newsletter August 2018 Issue (2018)
DSM in Animal Nutrition & Health. Riboflavin DSM (2017)
DSM in Animal Nutrition & Health. DSM Vitamin Supplementation Guidelines 2011 DSM (2017)
Z Cal, P Blumbergs, J Finnie, J Manavis, P Thompson.. Selective Vulnerability of Peripheral Nerves in Avian Riboflavin Deficiency Demyelinating Polyneuropathy Veterinary Pathology (2009)
Z. CAI, J. FINNIE, P. BLUMBERG Avian Riboflavin Deficiency: An Acquired Tomaculous Neuropathy. Veterinary Pathology (2006)
Powers, Hilary J.. Riboflavin (vitamin B-2) and health The American journal of clinical nutrition 77.6 (2003)
White HB 3rd. Sudden death of chicken embryos with hereditary riboflavin deficiency Journal of Nutrition (1996)
Abrams VA, Han CC, White HB 3rd. Riboflavin-deficient chicken embryos: hypoglycemia without dicarboxylic aciduria Comp Biochem Physiol B Biochem Mol Biol (1995)
National Academy. Nutrient Requirements of Poultry Washington, D.C. (1994)
W. Johnson, R. Storts. Peripheral Neuropathy Associated with Dietary Riboflavin Deficiency in the Chicken Veterinary Pathology (1988)
Summers, J. D., et al. Influence of vitamin deficiency and level of dietary protein on the incidence of leg problems in broiler chicks Poultry science (1984)
Gries CL, Scott ML. The pathology of thiamin, riboflavin, pantothenic acid and niacin deficiencies in the chick.. J Nutr (1972)
Maw, A. J. G. Inherited riboflavin deficiency in chicken eggs Poultry Science 33.1 (1954)

Geographical Distribution

Age Range

Newly hatched chicks are most susceptible.

Risk Factors

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.
Genetics - Commercial chicken breeds require additional riboflavin.