This is essential for normal growth and health. Deficiency results in condition in chicks 10-14 days old known as curled toe paralysis. Birds are unable to rise from their hocks but remain alert, the legs being outstretched with flaccid paralysis and frequent incoiling of the toes. Sciatic and brachial nerves are swollen and discoloured. Response to vitamin B2 is rapid. In newly hatched chicks, downfeathers are clubbed and glued together resulting in condition known as clubbed down.
Biotin
This is necessary for growth, food utilization, epidermal tissue sustenance, bone growth and development and reproduction. It is a cofactor for various carboxylation enzymes, two of the most relevant being pyruvate carboxylase (gluconeogenesis) and acetyl coenzyme A carboxylase (lipogenesis). In young birds deficiency signs include impaired feathering, periocular dermatitis, encrustations in beak and eyelid angles and on toes and footpads in early stages. Subsequently, there is depressed growth, heamorrhagic encrustation of the feet, poor feathering, parrot beak and abnormal bone formation. In adult breeder birds, severe deficiency results in reduced egg production and reduced hatchability. In young broilers, it may cause fatty liver kidney syndrome.
Choline
This is a lipotrophic factor involved in fat immobilization and it is a structural part of acetylcholine involved in nerve impulse transmission. Deficiency results in reduced growth, fatty liver, reduced hatchability and chondodystrophy.