Thiamin (vitamin B1) deficiency affects many systems of the chicken's body, including the muscles, heart, nerves, and digestive system.
Thiamin is one of the B vitamins and plays an important role in energy metabolism and tissue building. It combines with phosphate to form the coenzyme thiamin pyrophosphate (TPP), which is essential in reactions that produce energy from glucose or that convert glucose to fat for storage in the tissues. When there is not enough thiamin in the diet, these basic energy functions are disturbed, leading to problems throughout the body.
Chickens are more susceptible to neuromuscular effects of thiamine deficiency than mammals. Clinical signs of thiamin deficiency include ataxia (incoordination), ascending paralysis of the muscles (where chicks are seen sitting on their flexed legs), and drawing back their head in a stargazing position (which is often referred to as wry neck
) as a result of paralysis of the anterior neck muscles. At this stage, the chick soon loses the ability to stand or sit upright, and falls to the floor where it may lie with it's head still retracted. In adult chickens, polyneuritis is usually observed approximately three weeks after they are fed a thiamin-deficient diet. When breeding chickens don't have enough thiamin in their diet, it usually results in high mortality of embryos prior to hatching. Any chicks that do hatch will demonstrate clinical signs of severe thiamine deficiency.
Thiamin requirements for chickens generally range between 0.8-2.0 mg/kg (0.36 to 0.90 mg/lb). Light breeds (Leghorns) seem to have higher thiamin levels than heavy breeds. As the chicken ages, its need for thiamin increases because efficiency of vitamin utilization usually diminishes.