A Vitamin B2 or Vitamin E deficiency in chicks can cause a variety of nervous system symptoms including pulling their head/neck pulled towards the back, shivering, paralysis, and in worst cases death. These symptoms may begin to appear at 2 weeks of age. Be sure to use a high-quality poultry feed to ensure your little ones are getting the nutrition they need to thrive.
If you have a chick displaying symptoms of illness its best to separate it from the rest of its brooder mates. Providing an electrolyte free-choice is also suggested to encourage hydration. We also suggest contacting your local Agriculture Extension office to assist with a proper diagnosis and treatment plan.
Consumption of poisons such as pesticides can also cause nervous signs such as those listed. Be sure to keep pesticides in a safe place and clear of your poultry.
More detailed information can be found here.